151
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Yan J, Bouchard EF, Samassekou O, Chen BZ. Identification of a human chromosome-specific interstitial telomere-like sequence (ITS) at 22q11.2 using double-strand PRINS. Cytogenet Genome Res 2007; 116:29-37. [PMID: 17268175 DOI: 10.1159/000097415] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2006] [Accepted: 07/25/2006] [Indexed: 12/28/2022] Open
Abstract
Interstitial telomeric sequences (ITSs), telomere-like repeats at intrachromosomal sites, are common in mammals and consist of tandem repeats of the canonical telomeric repeat, TTAGGG, or a repeat similar to this. We report that the ITS in human chromosome region 22q11.2 is, in the sequenced genome database, 101 tandem repeats of the sequence TTAGGGAGG. Using the primed in situ labeling (PRINS) technique and primers against the canonical telomeric repeat (TTAGGG), we illuminated telomeric sites for all chromosomes and an ITS locus at 22q11.2. Using the TTAGGGAGG sequence, we designed PRINS primers that efficiently and specifically illuminate the 22q11.2 ITS locus without illuminating telomeric and other ITS loci. The 22q11.2 locus has more repeat units than other ITSs loci enabling an unprecedented high detection frequency for this interstitial telomere locus. The 22q11.2 is associated with hot spots for disease-related chromosome breaks for multiple disorders, such as DiGeorge syndrome and chronic myeloid leukemia. We describe our findings that the ITS at 22q11.2 is in the same area of, and proximal to the common rearrangement region of multiple disorders. We suggest that the ITS might be involved in DNA repair processes in this area to protect the chromosome from more serious damage.
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Affiliation(s)
- J Yan
- Service of Genetics, Department of Pediatrics, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Canada.
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152
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Sandrin-Garcia P, Richieri-Costa A, Tajara EH, Carvalho-Salles AB, Fett-Conte AC. Fluorescence in situ hybridization (FISH) screening for the 22q11.2 deletion in patients with clinical features of velocardiofacial syndrome but without cardiac anomalies. Genet Mol Biol 2007. [DOI: 10.1590/s1415-47572007000100006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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153
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Lee JA, Lupski JR. Genomic rearrangements and gene copy-number alterations as a cause of nervous system disorders. Neuron 2006; 52:103-21. [PMID: 17015230 DOI: 10.1016/j.neuron.2006.09.027] [Citation(s) in RCA: 199] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Genomic disorders are a group of human genetic diseases caused by genomic rearrangements resulting in copy-number variation (CNV) affecting a dosage-sensitive gene or genes critical for normal development or maintenance. These disorders represent a wide range of clinically distinct entities but include many diseases affecting nervous system function. Herein, we review selected neurodevelopmental, neurodegenerative, and psychiatric disorders either known or suggested to be caused by genomic rearrangement and CNV. Further, we emphasize the cause-and-effect relationship between gene CNV and complex disease traits. We also discuss the prevalence and heritability of CNV, the correlation between CNV and higher-order genome architecture, and the heritability of personality, behavioral, and psychiatric traits. We speculate that CNV could underlie a significant proportion of normal human variation including differences in cognitive, behavioral, and psychological features.
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Affiliation(s)
- Jennifer A Lee
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, 77030, USA
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154
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de La Rochebrochard C, Joly-Hélas G, Goldenberg A, Durand I, Laquerrière A, Ickowicz V, Saugier-Veber P, Eurin D, Moirot H, Diguet A, de Kergal F, Tiercin C, Mace B, Marpeau L, Frebourg T. The intrafamilial variability of the 22q11.2 microduplication encompasses a spectrum from minor cognitive deficits to severe congenital anomalies. Am J Med Genet A 2006; 140:1608-13. [PMID: 16761289 DOI: 10.1002/ajmg.a.31227] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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155
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Pavlicek A, House R, Gentles AJ, Jurka J, Morrow BE. Traffic of genetic information between segmental duplications flanking the typical 22q11.2 deletion in velo-cardio-facial syndrome/DiGeorge syndrome. Genome Res 2006; 15:1487-95. [PMID: 16251458 PMCID: PMC1310636 DOI: 10.1101/gr.4281205] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Velo-cardio-facial syndrome/DiGeorge syndrome results from unequal crossing-over events between two 240-kb low-copy repeats termed LCR22 (LCR22-2 and LCR22-4) on Chromosome 22q11.2, comprised of modules, each of which are >99% identical in sequence. To delineate regions in the LCR22s that might contain hotspots for 22q11.2 rearrangements, we scanned the interval for increased rates of recombination with the hypothesis that these regions might be more prone to breakage. We generated an algorithm to detect sites of altered recombination by searching for single nucleotide polymorphic positions in BAC clones from different libraries mapped to LCR22-2 and LCR22-4. This method distinguishes single nucleotide polymorphisms from paralogous sequence variants and complex polymorphic positions. Sites of shared polymorphism are considered potential sites of gene conversion or double cross-over between the two LCR22s. We found an inverse correlation between regions of paralogous sequence variants that are unique to a given position within one LCR22 and clusters of shared polymorphic sites, suggesting that these clusters depict altered recombination and not remnants of ancestral single nucleotide polymorphisms. We postulate that most shared polymorphic sites are products of past transfers of DNA information between the LCR22s, suggesting that frequent traffic of genetic material may induce genomic instability in the two LCR22s. We also found that gaps up to 1.5 kb long can be transferred between LCR22s.
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Affiliation(s)
- Adam Pavlicek
- Genetic Information Research Institute, Mountain View, California 94043, USA
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156
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Ming JE, Geiger E, James AC, Ciprero KL, Nimmakayalu M, Zhang Y, Huang A, Vaddi M, Rappaport E, Zackai EH, Shaikh TH. Rapid detection of submicroscopic chromosomal rearrangements in children with multiple congenital anomalies using high density oligonucleotide arrays. Hum Mutat 2006; 27:467-73. [PMID: 16619270 DOI: 10.1002/humu.20322] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Chromosomal rearrangements such as microdeletions and interstitial duplications are the underlying cause of many human genetic disorders. These disorders can manifest in the form of multiple congenital anomalies (MCA), which are a significant cause of morbidity and mortality in children. The major limitations of cytogenetic tests currently used for the detection of such chromosomal rearrangements are low resolution and limited coverage of the genome. Thus, it is likely that children with MCA may have submicroscopic chromosomal rearrangements that are not detectable by current techniques. We report the use of a commercially available, oligonucleotide-based microarray for genome-wide analysis of copy number alterations. First, we validated the microarray in patients with known chromosomal rearrangements. Next, we identified previously undetected, de novo chromosomal deletions in patients with MCA who have had a normal high-resolution karyotype and subtelomeric fluorescence in situ hybridization (FISH) analysis. These findings indicate that high-density, oligonucleotide-based microarrays can be successfully used as tools for the detection of chromosomal rearrangement in clinical samples. Their higher resolution and commercial availability make this type of microarray highly desirable for application in the diagnosis of patients with multiple congenital defects.
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Affiliation(s)
- Jeffrey E Ming
- Division of Human Genetics, Stokes Research Institute, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104, USA
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157
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Thomas NS, Durkie M, Potts G, Sandford R, Van Zyl B, Youings S, Dennis NR, Jacobs PA. Parental and chromosomal origins of microdeletion and duplication syndromes involving 7q11.23, 15q11-q13 and 22q11. Eur J Hum Genet 2006; 14:831-7. [PMID: 16617304 DOI: 10.1038/sj.ejhg.5201617] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Non-allelic homologous recombination between chromosome-specific LCRs is the most common mechanism leading to recurrent microdeletions and duplications. To look for locus-specific differences, we have used microsatellites to determine the parental and chromosomal origins of a large series of patients with de novo deletions of chromosome 7q11.23 (Williams syndrome), 15q11-q13 (Angelman syndrome, Prader-Willi syndrome) and 22q11 (Di George syndrome) and duplications of 15q11-q13. Overall the majority of rearrangements were interchromosomal, so arising from unequal meiotic exchange, and there were approximately equal numbers of maternal and paternal deletions. Duplications and deletions of 15q11-q13 appear to be reciprocal products that arise by the same mechanisms. The proportion arising from interchromosomal exchanges varied among deletions with 22q11 the highest and 15q11-q13 the lowest. However, parental and chromosomal origins were not always independent. For 15q11-q13, maternal deletions tended to be interchromosomal while paternal deletions tended to be intrachromosomal; for 22q11 there was a possible excess of maternal cases among intrachromosomal deletions. Several factors are likely to be involved in the formation of recurrent rearrangements and the relative importance of these appear to be locus-specific.
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Affiliation(s)
- N Simon Thomas
- Wessex Regional Genetics Laboratory, Salisbury District Hospital, Salisbury, UK.
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158
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Jolin EM, Weller EB, Weller RA. A biologic model to study the genetics of psychotic, mood, and anxiety disorders: the velocardiofacial syndrome. Curr Psychiatry Rep 2006; 8:90-5. [PMID: 16539882 DOI: 10.1007/s11920-006-0004-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Recent advances in molecular genetics have led to new insights on the velocardiofacial syndrome (VCFS). Most patients have a large deletion on one copy of chromosome 22 (encompassing up to 30 genes), which can be confirmed with genetic testing. A wide spectrum of psychiatric symptoms has been reported in patients with VCFS, including schizophrenia and bipolar disorder. Preliminary studies of candidate genes from the deletion region suggest that allelic differences may increase susceptibility to psychiatric disorders, but these studies await replication. Mouse models with genetically engineered deletions have the potential to isolate the genes associated with VCFS neuropsychiatric symptoms. VCFS is likely to represent the deficiency of several genes with complex interactions. Further psychiatric research is warranted to delineate more comprehensively the neuro-psychiatric phenotype associated with VCFS. Accurate psychiatric diagnosis will better inform and advance ongoing genetic research.
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Affiliation(s)
- Edith M Jolin
- Children's Hospital of Philadelphia, Department of Child and Adolescent Psychiatry, 3440 Market Street, Suite 200, Philadelphia, PA 19104, USA
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159
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Uddin RK, Zhang Y, Siu VM, Fan YS, O'Reilly RL, Rao J, Singh SM. Breakpoint Associated with a novel 2.3 Mb deletion in the VCFS region of 22q11 and the role of Alu (SINE) in recurring microdeletions. BMC MEDICAL GENETICS 2006; 7:18. [PMID: 16512914 PMCID: PMC1413517 DOI: 10.1186/1471-2350-7-18] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/29/2005] [Accepted: 03/02/2006] [Indexed: 11/10/2022]
Abstract
BACKGROUND Chromosome 22q11.2 region is highly susceptible to rearrangement, specifically deletions that give rise to a variety of genomic disorders including velocardiofacial or DiGeorge syndrome. Individuals with this 22q11 microdeletion syndrome are at a greatly increased risk to develop schizophrenia. METHODS Genotype analysis was carried out on the DNA from a patient with the 22q11 microdeletion using genetic markers and custom primer sets to define the deletion. Bioinformatic analysis was performed for molecular characterization of the deletion breakpoint sequences in this patient. RESULTS This 22q11 deletion patient was established to have a novel 2.3 Mb deletion with a proximal breakpoint located between genetic markers RH48663 and RH48348 and a distal breakpoint between markers D22S1138 and SHGC-145314. Molecular characterization of the sequences at the breakpoints revealed a 270 bp shared sequence of the breakpoint regions (SSBR) common to both ends that share >90% sequence similarity to each other and also to short interspersed nuclear elements/Alu elements. CONCLUSION This Alu sequence like SSBR is commonly in the proximity of all known deletion breakpoints of 22q11 region and also in the low copy repeat regions (LCRs). This sequence may represent a preferred sequence in the breakpoint regions or LCRs for intra-chromosomal homologous recombination mechanisms resulting in common 22q11 deletion.
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Affiliation(s)
- Raihan K Uddin
- Department of Biology, University of Western Ontario, London, Ontario, N6A 5B7, Canada
| | - Yang Zhang
- Department of Biology, University of Western Ontario, London, Ontario, N6A 5B7, Canada
| | - Victoria Mok Siu
- Division of Medical Genetics, University of Western Ontario, London, Ontario, N6A 5B7, Canada
| | - Yao-Shan Fan
- Division of Medical Genetics, University of Western Ontario, London, Ontario, N6A 5B7, Canada
| | - Richard L O'Reilly
- Department of Psychiatry, University of Western Ontario, London, Ontario, N6A 5B7, Canada
| | - Jay Rao
- Department of Psychiatry, University of Western Ontario, London, Ontario, N6A 5B7, Canada
| | - Shiva M Singh
- Department of Biology, University of Western Ontario, London, Ontario, N6A 5B7, Canada
- Division of Medical Genetics, University of Western Ontario, London, Ontario, N6A 5B7, Canada
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160
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Holländer G, Gill J, Zuklys S, Iwanami N, Liu C, Takahama Y. Cellular and molecular events during early thymus development. Immunol Rev 2006; 209:28-46. [PMID: 16448532 DOI: 10.1111/j.0105-2896.2006.00357.x] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The thymic stromal compartment consists of several cell types that collectively enable the attraction, survival, expansion, migration, and differentiation of T-cell precursors. The thymic epithelial cells constitute the most abundant cell type of the thymic microenvironment and can be differentiated into morphologically, phenotypically, and functionally separate subpopulations of the postnatal thymus. All thymic epithelial cells are derived from the endodermal lining of the third pharyngeal pouch. Very soon after the formation of a thymus primordium and prior to its vascularization, thymic epithelial cells orchestrate the first steps of intrathymic T-cell development, including the attraction of lymphoid precursor cells to the thymic microenvironment. The correct segmentation of pharyngeal epithelial cells and their subsequent crosstalk with cells in the pharyngeal arches are critical prerequisites for the formation of a thymus anlage. Mutations in several transcription factors and their target genes have been informative to detail some of the complex mechanisms that control the development of the thymus anlage. This review highlights recent findings related to the genetic control of early thymus organogenesis and provides insight into the molecular basis by which lymphocyte precursors are attracted to the thymus.
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Affiliation(s)
- Georg Holländer
- Pediatric Immunology, The Center for Biomedicine, Department of Clinical-Biological Sciences, University of Basel, and The University Children's Hospital of Basel, Basel, Switzerland.
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161
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Jiang L, Duan C, Chen B, Hou Z, Chen Z, Li Y, Huan Y, Wu KK. Association of 22q11 deletion with isolated congenital heart disease in three Chinese ethnic groups. Int J Cardiol 2006; 105:216-23. [PMID: 16243116 DOI: 10.1016/j.ijcard.2005.01.012] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/25/2004] [Revised: 01/06/2005] [Accepted: 01/12/2005] [Indexed: 01/18/2023]
Abstract
BACKGROUND Congenital heart disease (CHD) is the most common type of heart disease among children. About 75% of DiGeorge syndrome (DGS) and velo-cardio-facial syndrome (VCFS) includes CHD. A deletion within chromosome 22q11.2 has been identified in the majority of patients with DGS and VCFS. And 22q11.2 deletion has become one of the markers used to study CHD in these syndromes. Whether 22q11.2 deletion is associated with isolated CHD is not known and was the topic of this study. METHODS AND RESULTS We studied the 22q11.2 deletion in three Chinese ethnic groups (Tai, Bai and Han people) with 19 sporadic, isolated CHD by genotype and haplotype analysis with D22S420 etc. 11 consecutive polymorphic microsatellite markers. Among 19 isolated CHD patients, four had Tetralogy of Fallot (TOF), five exhibited Ventricular Septal Defect (VSD), five showed Atrial Septal Defect (ASD) and 5 had Patent Ductus Arteriosus (PDA). In some isolated CHD patients, 3 Mb and 1.5 Mb deletion to chromosome 22q11.2 was found. 2 of 4 TOF (50%) and 1 of 5 VSD (20%) and 1 of 5 PDA (20%) respectively were found to have deletions at D22S944. CONCLUSIONS 22q11.2 deletion can be detected in isolated TOF, VSD and PDA of three Chinese ethnic groups, without detectable 22q11.2 deletion in those isolated ASD patients examined thus far. Our finding may be the first to show the 22q11.2 deletion in sporadic, isolated PDA/VSD patients whose family members are without CHD. In addition, D22S420 etc. 11 consecutive polymorphic microsatellite markers are very useful for the determination of 22q11.2 deletion in isolated CHD in China.
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Affiliation(s)
- Lihong Jiang
- Department of Ecology and Environmental Sciences, College of Life Sciences, Yunnan University, Kunming, Yunnan 650091, P.R. China.
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162
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Brunet A, Gabau E, Perich RM, Valdesoiro L, Brun C, Caballín MR, Guitart M. Microdeletion and microduplication 22q11.2 screening in 295 patients with clinical features of DiGeorge/Velocardiofacial syndrome. Am J Med Genet A 2006; 140:2426-32. [PMID: 17041934 DOI: 10.1002/ajmg.a.31499] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The 22q11.2 region is susceptible to chromosomal rearrangements, leading to various types of congenital malformation and mental retardation. The most common anomaly is 22q11.2 microdeletion, associated with DiGeorge/Velocardiofacial syndrome (DG/VCFS). Recently the microduplication 22q11.2 syndrome has been identified. Some clinical features in patients with this new chromosomal disorder present a substantial overlap with DG/VCFS. The aim of this hospital-based study was to evaluate the incidence of deletions and duplications on 22q11.2 in patients with DG/VCFS features. We investigated a group of 295 patients with widely variable manifestations associated with DG/VCFS. Along with the clinical diagnoses different anomalies were noted such as conotruncal cardiac anomaly, velopharyngeal insufficiency, characteristic facial dysmorphic features, language impairment, developmental delay/learning difficulties, and immunologic anomalies or thymic hypoplasia. Laboratory studies included conventional cytogenetic and FISH testing. Metaphase and interphase cells were analyzed for the presence of 22q11.2 microdeletion or microduplication. There were 12 patients who carried 22q11.2 microdeletion and no microduplication in the region was identified. Other chromosomal anomalies were reported in five patients with an overlapped DG/VCFS phenotype. All patients with 22q11.2 microdeletion showed a characteristic phenotype of DG/VCFS. We did not identify 22q11.2 microduplication, suggesting that this is a rare event in patients with DG/VCFS features.
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Affiliation(s)
- Anna Brunet
- Laboratori de Genètica, UDIAT-Centre Diagnòstic, Servei de Pediatria, Fundació Parc Taulí Institut Universitari UAB, Corporació Sanitària Parc Taulí, Sabadell, Spain.
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163
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Chen YF, Kou PL, Tsai SJ, Chen KF, Chan HH, Chen CM, Sun HS. Computational analysis and refinement of sequence structure on chromosome 22q11.2 region: application to the development of quantitative real-time PCR assay for clinical diagnosis. Genomics 2005; 87:290-7. [PMID: 16307865 DOI: 10.1016/j.ygeno.2005.10.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2005] [Revised: 09/29/2005] [Accepted: 10/06/2005] [Indexed: 02/09/2023]
Abstract
The low-copy repeat (LCR) is a new class of repetitive DNA element and has been implicated in many human disorders, including DiGeorge/velocardiofacial syndrome (DGS/VCFS). It is now recognized that nonallelic homologous recombination (NAHR) through LCRs flanking the chromosome 22q11.2 region leads to genome rearrangements and results in the DGS/VCFS. To refine the structure and content of chromosome 22q11.2 LCRs, we applied computational analysis to dissect region-specific LCRs using publicly available sequences. Nine distinct duplicons between 1.6 and 65 kb long and sharing >95% sequence identity were identified. The presence of these sequence motifs supports the NAHR mechanism. Further sequence analysis suggested that the previously defined 3-Mb deletion may actually comprise two deletion intervals of similar size close to each other and thus indistinguishable when using fluorescence in situ hybridization (FISH) analysis. The differentially deleted regions contain several hypothetical proteins and UniGene clusters and may partially explain the clinical heterogeneity observed in DGS/VCFS patients with the 3-Mb common deletion. To implement further sequence information in molecular medicine, we designed a real-time quantitative PCR assay and validated the method in 122 patients with suspected DGS/VCFS. The assay detected 28 patients with chromosome 22q11.2 deletion later confirmed using FISH. Our results indicated that the developed assay is reliable as well as time and cost effective for clinical diagnosis of chromosome 22q11.2 deletion. They also suggest that this methodology can be applied to develop a molecular approach for clinical detection and diagnosis of other genomic disorders.
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Affiliation(s)
- Ying-Fan Chen
- Institute of Basic Medical Sciences, National Cheng Kung University Medical College, Tainan 70101, Taiwan
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164
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Baldini A. Dissecting contiguous gene defects: TBX1. Curr Opin Genet Dev 2005; 15:279-84. [PMID: 15917203 DOI: 10.1016/j.gde.2005.03.001] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2005] [Accepted: 03/17/2005] [Indexed: 10/25/2022]
Abstract
DiGeorge syndrome is mainly caused by a multigene, heterozygous, interstitial chromosomal deletion. Of the approximately 30 deleted genes, Tbx1 is the only gene that, after an extensive functional analysis in the mouse, has been found to be haploinsufficient. The mutant phenotype is convincingly similar to the human syndrome, and its human homolog, TBX1, is the only gene for which mutations have been found in some patients without the chromosomal deletion. The research interest in this syndrome is driven not only by the obvious clinical significance of the disease but also by a broader biological importance. In particular, this syndrome is the most typical developmental defect of the embryonic pharyngeal system: a transient, vertebrate-specific structure that contributes to diverse tissues of the head, neck and thorax. Many birth defects, including a large fraction of congenital heart disease cases, derive from developmental problems of the pharyngeal system. Tbx1 is an excellent tool to probe the genetic network governing embryonic pharyngeal development.
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Affiliation(s)
- Antonio Baldini
- Center for Cardiovascular Development, Department of Pediatrics (Cardiology), Baylor College of Medicine, Houston, TX 77030, USA.
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165
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Cotter PD, Nguyen H, Tung G, Rauen KA. Incidence of microduplication 22q11.2 in patients referred for FISH testing for velo cardiofacial and DiGeorge syndromes. Eur J Hum Genet 2005; 13:1245-6. [PMID: 16175191 DOI: 10.1038/sj.ejhg.5201494] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
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166
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Sharp AJ, Locke DP, McGrath SD, Cheng Z, Bailey JA, Vallente RU, Pertz LM, Clark RA, Schwartz S, Segraves R, Oseroff VV, Albertson DG, Pinkel D, Eichler EE. Segmental duplications and copy-number variation in the human genome. Am J Hum Genet 2005; 77:78-88. [PMID: 15918152 PMCID: PMC1226196 DOI: 10.1086/431652] [Citation(s) in RCA: 682] [Impact Index Per Article: 35.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2005] [Accepted: 05/04/2005] [Indexed: 01/15/2023] Open
Abstract
The human genome contains numerous blocks of highly homologous duplicated sequence. This higher-order architecture provides a substrate for recombination and recurrent chromosomal rearrangement associated with genomic disease. However, an assessment of the role of segmental duplications in normal variation has not yet been made. On the basis of the duplication architecture of the human genome, we defined a set of 130 potential rearrangement hotspots and constructed a targeted bacterial artificial chromosome (BAC) microarray (with 2,194 BACs) to assess copy-number variation in these regions by array comparative genomic hybridization. Using our segmental duplication BAC microarray, we screened a panel of 47 normal individuals, who represented populations from four continents, and we identified 119 regions of copy-number polymorphism (CNP), 73 of which were previously unreported. We observed an equal frequency of duplications and deletions, as well as a 4-fold enrichment of CNPs within hotspot regions, compared with control BACs (P < .000001), which suggests that segmental duplications are a major catalyst of large-scale variation in the human genome. Importantly, segmental duplications themselves were also significantly enriched >4-fold within regions of CNP. Almost without exception, CNPs were not confined to a single population, suggesting that these either are recurrent events, having occurred independently in multiple founders, or were present in early human populations. Our study demonstrates that segmental duplications define hotspots of chromosomal rearrangement, likely acting as mediators of normal variation as well as genomic disease, and it suggests that the consideration of genomic architecture can significantly improve the ascertainment of large-scale rearrangements. Our specialized segmental duplication BAC microarray and associated database of structural polymorphisms will provide an important resource for the future characterization of human genomic disorders.
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Affiliation(s)
- Andrew J Sharp
- Department of Genome Sciences, University of Washington School of Medicine, Seattle, WA 98195, USA
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167
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Yobb TM, Somerville MJ, Willatt L, Firth HV, Harrison K, MacKenzie J, Gallo N, Morrow BE, Shaffer LG, Babcock M, Chernos J, Bernier F, Sprysak K, Christiansen J, Haase S, Elyas B, Lilley M, Bamforth S, McDermid HE. Microduplication and triplication of 22q11.2: a highly variable syndrome. Am J Hum Genet 2005; 76:865-76. [PMID: 15800846 PMCID: PMC1199375 DOI: 10.1086/429841] [Citation(s) in RCA: 180] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2004] [Accepted: 02/21/2005] [Indexed: 12/17/2022] Open
Abstract
22q11.2 microduplications of a 3-Mb region surrounded by low-copy repeats should be, theoretically, as frequent as the deletions of this region; however, few microduplications have been reported. We show that the phenotype of these patients with microduplications is extremely diverse, ranging from normal to behavioral abnormalities to multiple defects, only some of which are reminiscent of the 22q11.2 deletion syndrome. This diversity will make ascertainment difficult and will necessitate a rapid-screening method. We demonstrate the utility of four different screening methods. Although all the screening techniques give unique information, the efficiency of real-time polymerase chain reaction allowed the discovery of two 22q11.2 microduplications in a series of 275 females who tested negative for fragile X syndrome, thus widening the phenotypic diversity. Ascertainment of the fragile X-negative cohort was twice that of the cohort screened for the 22q11.2 deletion. We also report the first patient with a 22q11.2 triplication and show that this patient's mother carries a 22q11.2 microduplication. We strongly recommend that other family members of patients with 22q11.2 microduplications also be tested, since we found several phenotypically normal parents who were carriers of the chromosomal abnormality.
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Affiliation(s)
- Twila M Yobb
- Department of Biological Sciences, University of Alberta, Edmonton, Canada
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168
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Gentile M, Wuyts W, Grittani S, Di Carlo A, Cariola F, Verdyck P, Margari L, Perniola T, Buonadonna AL. Clinical, cytogenetic, and molecular characterization of a patient with a de novo interstitial 22q12 duplication. Am J Med Genet A 2005; 127A:186-90. [PMID: 15108208 DOI: 10.1002/ajmg.a.20672] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
We report a 19-year-old woman with minor craniofacial anomalies, mild mental retardation, and foramina parietalia permagna (FPP) (OMIM 168500). Cytogenetic analysis showed a de novo interstitial chromosome 22 long arm duplication. FISH with a panel of chromosome 22q12-q13 bands-specific BAC clones refined the cytogenetic investigation, and restricted the duplicated segment to the q12 region. Mutation analysis of FPP genes identified an insertion mutation in the ALX4 gene (344insC) in the proband and her father with loss of function of the gene. The patient's phenotype is considered in the light of the results of the cytogenetic, FISH, and molecular investigations, and her features are compared with those of other patients with similar duplications. Finally, variable phenotypic findings due to different 22q duplicated chromosomal segments are discussed. Our report indicates that 22q12 interstitial duplications are associated with craniofacial anomalies and mild mental retardation, while life threatening malformations are usually not present. Although these phenotypic changes are common and non-specific, molecular study of our patient established more precise relationships between clinical findings and 22q duplicated region(s). This approach fosters better counseling of the families of patients with newly diagnosed, similar duplications.
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Affiliation(s)
- M Gentile
- Department of Medical Genetics, I.R.C.C.S. Saverio de Bellis, via della Resistenza, 70013 Castellana Grotte (BA), Italy.
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169
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Gentile M, De Sanctis S, Cariola F, Spezzi T, Di Carlo A, Tontoli F, Lista F, Buonadonna AL. FISH approach to determine cat eye syndrome chromosome breakpoints of a patient with cat eye syndrome type II. Eur J Med Genet 2005; 48:33-9. [PMID: 15953404 DOI: 10.1016/j.ejmg.2005.01.020] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2004] [Accepted: 10/20/2004] [Indexed: 11/19/2022]
Abstract
We report a 19-year-old man with craniofacial dysmorphic features, anorectal malformations, eye colobomas, orthopaedic anomalies, and mild neurodevelopmental delay. Cat eye syndrome (CES) was suspected, and confirmed by cytogenetic analysis which showed the presence of a supernumerary bisatellited chromosome, identified by fluorescence in situ hybridization (FISH) as invdup(22). The marker was further analyzed with six BAC clones located at the 22q11.1 and 22q11.2 regions; this analysis allowed correct assignment at low copy repeat 4 on chromosome 22 (LCR22-4) of the two breakpoints, confirming the presence of a CES chromosome type II. The patient's phenotype is considered in the light of the cytogenetic, and FISH investigations results and other patients reported in literature. Molecular definition of the breakpoints at the LCR22-4 copy confirms the role of different chromosome 22-specific LCRs in CES chromosomes generation, as well as in other chromosome 22 germ line rearrangements. Our report confirms that, unlike other conditions, i.e. the invdup(15) bisatellited dicentric marker, the CES phenotype does not appear to correlate with the size of the marker chromosome. Additional cases are necessary to be able to draw more specific genotype-phenotype correlations and to determine the outcome of patients with CES, especially when this rare condition is diagnosed in prenatal age.
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Affiliation(s)
- M Gentile
- Department of Medical Genetics, I.R.C.C.S. Saverio de Bellis, 70013 Castellana Grotte (BA), Italy.
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170
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Karayiorgou M, Gogos JA. The molecular genetics of the 22q11-associated schizophrenia. ACTA ACUST UNITED AC 2005; 132:95-104. [PMID: 15582150 DOI: 10.1016/j.molbrainres.2004.09.029] [Citation(s) in RCA: 120] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/27/2004] [Indexed: 01/04/2023]
Abstract
Schizophrenia has a strong genetic component but the mode of inheritance of the disease is complex and in all likelihood involves interaction among multiple genes and also possibly environmental or stochastic factors. A number of studies have shown that the 22q11 deletion syndrome (22q11DS) is a true genetic subtype of schizophrenia and as such may play an extremely important role in deciphering the genetic basis of schizophrenia. Microdeletions of the 22q11 locus are associated with a staggering increased risk to develop schizophrenia. The same locus has also been implicated by some linkage studies. Systematic examination of individual genes from the 1.5 Mb critical region has identified so far the PRODH and ZDHHC8 as strong candidate schizophrenia susceptibility genes from this locus. Discovery of these genes implicates neuromodulatory aminoacids and protein palmitoylation as important for disease development. Other genes, including the gene encoding for COMT, have been implicated by candidate gene approaches. It therefore appears that the 22q11-associated schizophrenia may have the characteristics of a contiguous gene syndrome, where deficiency in more than one gene contributes to the strikingly increased disease risk. Mouse models for individual candidate genes will provide the investigators with the opportunity to start understanding the function of these genes and how they may impact on schizophrenia. Mouse models that carry long-range deletions will likely capture the interactions among the culprit genes and help explain the genetic contribution of this locus to the high risk for schizophrenia. In-depth human and animal model studies of 22q11DS promise to answer critical questions relating to the devastating illness of schizophrenia, whose causes remain largely unknown.
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Affiliation(s)
- Maria Karayiorgou
- Laboratory of Human Neurogenetics, The Rockefeller University, New York, NY 10021, USA.
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171
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Kotzot D, Haberlandt E, Fauth C, Baumgartner S, Scholl-Bürgi S, Utermann G. Del(18)(q12.2q21.1) caused by a paternal sister chromatid rearrangement in a developmentally delayed girl. Am J Med Genet A 2005; 135:304-7. [PMID: 15887269 DOI: 10.1002/ajmg.a.30727] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Monosomy of 18q12.3 has been reported in only 16 cases, in one as a mosaic with a normal cell line. Abnormal behaviour, developmental delay, normal measurements, and minor facial anomalies including ptosis, bilateral epicanthus, strabismus, short and slightly down-slanting palpebral fissures, and full cheeks are characteristic manifestations. We report on a 26-month-old girl with del(18)(q12.2q21.1) and typical phenotype. Microsatellite mediated haplotype analysis showed approximately 12 Mb deletion and demonstrated that the deletion was most likely formed during paternal meiosis by a rearrangement between the grandpaternal sister chromatids.
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Affiliation(s)
- Dieter Kotzot
- Institute of Medical Biology and Human Genetics, Medical University of Innsbruck, Innsbruck, Austria.
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172
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Wieser R, Fritz B, Ullmann R, Müller I, Galhuber M, Storlazzi CT, Ramaswamy A, Christiansen H, Shimizu N, Rehder H. Novel rearrangement of chromosome band 22q11.2 causing 22q11 microdeletion syndrome-like phenotype and rhabdoid tumor of the kidney. Hum Mutat 2005; 26:78-83. [PMID: 15957176 DOI: 10.1002/humu.20195] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The 22q11.2 microdeletion syndrome is the most frequent microdeletion syndrome in humans, yet its genetic basis is complex and is still not fully understood. Most patients harbor a 3-Mb deletion (typically deleted region [TDR]), but occasionally patients with atypical deletions, some of which do not overlap with each other and/or the TDR, have been described. Microduplication of the TDR leads to a phenotype similar, albeit not identical, to the deletion of this region. Here we present a child initially suspected of having 22q11 microdeletion syndrome, who in addition developed a fatal malignant rhabdoid tumor of the kidney. Detailed cytogenetic and molecular analyses revealed a complex de novo rearrangement of band q11 of the paternally derived chromosome 22. This aberration exhibited two novel features. First, a microduplication of the 22q11 TDR was associated with an atypical 22q11 microdeletion immediately telomeric of the duplicated region. Second, this deletion was considerably larger than previously reported atypical 22q11 deletions, spanning 2.8 Mb and extending beyond the SMARCB1/SNF5/INI1 tumor suppressor gene, whose second allele harbored a somatic frameshift-causing sequence alteration in the patient's tumor. Two nonallelic homologous recombination events between low-copy repeats (LCRs) could explain the emergence of this novel and complex mutation associated with the phenotype of 22q11 microdeletion syndrome.
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Affiliation(s)
- R Wieser
- Abteilung für Humangenetik, Klinisches Institut für Medizinische und Chemische Labordiagnostik, Medizinische Universität Wien, Wien, Austria.
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173
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Morrissette JJD, Medne L, Bentley T, Owens NL, Geiger E, Pipan M, Zackai EH, Shaikh T, Spinner NB. A patient with mosaic partial trisomy 18 resulting from dicentric chromosome breakage. Am J Med Genet A 2005; 137:208-12. [PMID: 16082706 DOI: 10.1002/ajmg.a.30845] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
We present a patient with minor dysmorphic features and a mosaic karyotype with two different abnormal cell lines, both involving abnormalities of chromosome 18. Twenty percent of cells studied (4/20) had 46 chromosomes with a large derivative pseudoisodicentric chromosome 18. This chromosome was deleted for 18pter and duplicated for part of proximal 18p (18p11.2 based on fluorescence in situ hybridization (FISH) studies and all of 18q. The two copies of portions of chromosome 18 were fused in an inverted fashion (duplicated for 18qter->18p11.3). The smaller der(18) was present in 80% of cells studied (16/20) and had a normal q-arm, while the p-arm was missing the subtelomere region but had duplication of a part of 18p. FISH studies showed that the larger derivative 18 contained the 18q subtelomere at each end, but the 18p subtelomere was absent, consistent with fusion of two regions within 18p resulting in deletion of the subtelomeric regions. The smaller der(18) was also missing the 18p subtelomere (with normal 18q as expected). Further testing with BAC clones mapping within 18p11.2 showed that these sequences were duplicated and inverted in both of the der(18)s. These findings lead us to hypothesize that the smaller der(18) was derived from the larger, dicentric 18 following anaphase bridge formation, with breakage distal to the duplicated segment.
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Affiliation(s)
- Jennifer J D Morrissette
- Division of Human Genetics and Molecular Biology, 1007A Abramson Research Center, Children's Hospital of Philadelphia, 34th Street & Civic Center Boulevard, Philadelphia, PA 19104, USA
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174
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Portnoï MF, Lebas F, Gruchy N, Ardalan A, Biran-Mucignat V, Malan V, Finkel L, Roger G, Ducrocq S, Gold F, Taillemite JL, Marlin S. 22q11.2 duplication syndrome: Two new familial cases with some overlapping features with DiGeorge/velocardiofacial syndromes. Am J Med Genet A 2005; 137:47-51. [PMID: 16007629 DOI: 10.1002/ajmg.a.30847] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Twenty-one patients, including our two cases, with variable clinical phenotype, ranging from mild learning disability to severe congenital malformations or overlapping features with DiGeorge/velocardiofacial syndromes (DG/VCFS), have been shown to have a chromosome duplication 22q11 of the region that is deleted in patients with DG/VCFS. The reported cases have been identified primarily by interphase FISH and could have escaped identification and been missed by routine cytogenetic analysis. Here we report on two inherited cases, referred to us, to rule out 22q11 microdeletion diagnosis of VCFS. The first patient was a 2-month-old girl, who presented with cleft palate, minor dysmorphic features including short palpebral fissures, widely spaced eyes, long fingers, and hearing loss. Her affected mother had mild mental retardation and learning disabilities. The second patient was a 7(1/2)-year-old boy with velopharyngeal insufficiency and mild developmental delay. He had a left preauricular tag, bifida uvula, bilateral fifth finger clinodactyly, and bilateral cryptorchidism. His facial features appeared mildly dysmorphic with hypertelorism, large nose, and micro/retrognathia. The affected father had mild mental retardation and had similar facial features. FISH analysis of interphase cells showed three TUPLE1-probe signals with two chromosome-specific identification probes in each cell. FISH analysis did not show the duplication on the initial testing of metaphase chromosomes. On review, band q11.2 was brighter on one chromosome 22 in some metaphase spreads. The paucity of reported cases of 22q11.2 microduplication likely reflects a combination of phenotypic diversity and the difficulty of diagnosis by FISH analysis on metaphase spreads. These findings illustrate the importance of scanning interphase nuclei when performing FISH analysis for any of the genomic disorders.
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175
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Adeyinka A, Stockero KJ, Flynn HC, Lorentz CP, Ketterling RP, Jalal SM. Familial 22q11.2 deletions in DiGeorge/velocardiofacial syndrome are predominantly smaller than the commonly observed 3Mb. Genet Med 2004; 6:517-20. [PMID: 15545748 DOI: 10.1097/01.gim.0000144011.97407.b6] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
PURPOSE DiGeorge/velocardiofacial syndrome (DG/VCFS) is the most common cytogenetically characterized microdeletion of 22q11.2 region. In approximately 90% of patients, the deletion size is 3 Mb, whereas the remaining range from 1.5 to 2.5 Mb. The purpose of this study was to test the hypothesis that small deletions may be more easily tolerated in a familial fashion than larger deletions, especially for this syndrome. METHOD Sixteen FISH probes designed from bacterial artificial chromosomes (BACs) and P1 artificial chromosomes (PACs) mapped to 22q11.2 were used to determine the deletion sizes in 22 individuals from ten families with familial 22q11.2 deletion detected by standard FISH tests. RESULT Seven families had deletions of < 3 Mb ( approximately 1.5 Mb) in size and 3 families had the common 3-Mb deletion. The 70% frequency of smaller sized deletions among this group of patients with familial del(22)(q11.2) is significantly higher than that reported among unselected group of patients with del(22)(q11.2) (P < 0.0001, Fisher exact test). CONCLUSION Familial del(22)(q11.2) are predominantly smaller than the common deletion size of 3 Mb, indicating that there may be some underlying mechanisms that favor parent-to-child transmission of smaller deletions in individuals with del(22)(q11.2), therefore, underscoring the need to exclude a familial basis in cases of del(22)(q11.2) smaller than 3 Mb.
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Affiliation(s)
- Adewale Adeyinka
- Cytogenetics Laboratory Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota, USA
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176
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Mewborn SK, Lese Martin C, Ledbetter DH. The dynamic nature and evolutionary history of subtelomeric and pericentromeric regions. Cytogenet Genome Res 2004; 108:22-5. [PMID: 15545712 DOI: 10.1159/000080798] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2004] [Accepted: 02/06/2004] [Indexed: 02/02/2023] Open
Abstract
The organization and evolution of the subtelomeric and pericentromeric regions of human chromosomes exhibit unique characteristics compared to other regions of the genome. As shown in Fig. 1 the functional elements of the centromere and telomere are comprised of highly repetitive DNA sequences, which are responsible for carrying out the main mechanistic duties of these two regions: chromosome segregation and end replication, respectively. The nature of the repeats in these two regions and their function have been reviewed separately and, therefore, will not be discussed in more detail here (Sullivan et al., 1996, 2001; McEachern et al., 2000; Henikoff et al., 2001). Adjacent to these functional element regions, the centromere and telomere regions share an interesting architecture as depicted in Fig. 1. For both pericentromeric and subtelomeric regions, blocks of recent genomic duplications form a zone of shared sequence homologies between certain subsets of human chromosomes. The dynamic nature and evolutionary history of these regions and the unique DNA sequence adjacent to them will be the focus of this review.
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Affiliation(s)
- S K Mewborn
- Department of Human Genetics, University of Chicago, Chicago, IL, USA
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177
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Bailey JA, Eichler EE. Genome-wide detection and analysis of recent segmental duplications within mammalian organisms. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2004; 68:115-24. [PMID: 15338609 DOI: 10.1101/sqb.2003.68.115] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Affiliation(s)
- J A Bailey
- Department of Genetics, Center for Computational Genomics, Case Western Reserve University School of Medicine and University Hospitals of Cleveland, Cleveland, Ohio 44106, USA
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178
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Kehrer-Sawatzki H, Kluwe L, Sandig C, Kohn M, Wimmer K, Krammer U, Peyrl A, Jenne DE, Hansmann I, Mautner VF. High frequency of mosaicism among patients with neurofibromatosis type 1 (NF1) with microdeletions caused by somatic recombination of the JJAZ1 gene. Am J Hum Genet 2004; 75:410-23. [PMID: 15257518 PMCID: PMC1182020 DOI: 10.1086/423624] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2004] [Accepted: 06/21/2004] [Indexed: 11/03/2022] Open
Abstract
Detailed analyses of 20 patients with sporadic neurofibromatosis type 1 (NF1) microdeletions revealed an unexpected high frequency of somatic mosaicism (8/20 [40%]). This proportion of mosaic deletions is much higher than previously anticipated. Of these deletions, 16 were identified by a screen of unselected patients with NF1. None of the eight patients with mosaic deletions exhibited the mental retardation and facial dysmorphism usually associated with NF1 microdeletions. Our study demonstrates the importance of a general screening for NF1 deletions, regardless of a special phenotype, because of a high estimated number of otherwise undetected mosaic NF1 microdeletions. In patients with mosaicism, the proportion of cells with the deletion was 91%-100% in peripheral leukocytes but was much lower (51%-80%) in buccal smears or peripheral skin fibroblasts. Therefore, the analysis of other tissues than blood is recommended, to exclude mosaicism with normal cells in patients with NF1 microdeletions. Furthermore, our study reveals breakpoint heterogeneity. The classic 1.4-Mb deletion was found in 13 patients. These type I deletions encompass 14 genes and have breakpoints in the NF1 low-copy repeats. However, we identified a second major type of NF1 microdeletion, which spans 1.2 Mb and affects 13 genes. This type II deletion was found in 8 (38%) of 21 patients and is mediated by recombination between the JJAZ1 gene and its pseudogene. The JJAZ1 gene, which is completely deleted in patients with type I NF1 microdeletions and is disrupted in deletions of type II, is highly expressed in brain structures associated with learning and memory. Thus, its haploinsufficiency might contribute to mental impairment in patients with constitutional NF1 microdeletions. Conspicuously, seven of the eight mosaic deletions are of type II, whereas only one was a classic type I deletion. Therefore, the JJAZ1 gene is a preferred target of strand exchange during mitotic nonallelic homologous recombination. Although type I NF1 microdeletions occur by interchromosomal recombination during meiosis, our findings imply that type II deletions are mediated by intrachromosomal recombination during mitosis. Thus, NF1 microdeletions acquired during mitotic cell divisions differ from those occurring in meiosis and are caused by different mechanisms.
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179
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Wiehahn GJ, Bosch GP, du Preez RR, Pretorius HW, Karayiorgou M, Roos JL. Assessment of the frequency of the 22q11 deletion in Afrikaner schizophrenic patients. Am J Med Genet B Neuropsychiatr Genet 2004; 129B:20-2. [PMID: 15274032 DOI: 10.1002/ajmg.b.20168] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A hemizygous deletion of the q11 band on chromosome 22 occurs in 1 of every 5,950 live births (0.017%). The deletion is mediated by low copy repeats (LCRs) flanking this locus. Presence of the deletion is associated with variable phenotypic expression, which can include distinctive facial dysmorphologies, congenital heart disease and learning disabilities. An unusually high percentage of individuals with this deletion (25-30%) have been described to develop schizophrenia or schizoaffective disorder. In previous studies, the prevalence of the 22q11 deletion in patients with schizophrenia was found to be approximately 2% in Caucasian adults and 6% in childhood-onset cases. Both these frequencies represent a dramatic increase from the prevalence of the deletion in the general population. In this study, we investigate the occurrence of the 22q11 deletion in an independent sample of schizophrenic patients of Afrikaner origin. We first ascertained a sample of 85 patients who meet full diagnostic criteria for schizophrenia for presence of two or more of the clinical features associated with presence of the 22q11 deletion. A group of six patients (7%) met these criteria. This group was subjected to fluorescent in situ hybridization (FISH) and presence of the 22q11 deletion was confirmed for two subjects. Our study therefore confirms the previously reported rate of 2% frequency of the 22q11 deletion in adult schizophrenic patients and provides a two-stage screening protocol to identify these patients.
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Affiliation(s)
- G J Wiehahn
- University of Pretoria Department of Psychiatry & Weskoppies Hospital, Pretoria, Republic of South Africa
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180
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Rauch A, Hofbeck M, Cesnjevar R, Koch A, Rauch R, Buheitel G, Singer H, Weyand M. Search for somatic 22q11.2 deletions in patients with conotruncal heart defects. Am J Med Genet A 2004; 124A:165-9. [PMID: 14699615 DOI: 10.1002/ajmg.a.20323] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
A wide range of clinical variability in patients with 22q11.2 deletions has been demonstrated in numerous studies. Nevertheless, it is still an open question if major genetic factors contribute to clinical expression. Therefore one aim of this study was to investigate, if patients with 22q11.2 deletion and conotruncal heart defects show a "second hit" somatic 22q11.2 deletion in tissue from the conotruncus, heart vessels or thymus. The second aim was to analyse patients with conotruncal heart defects without 22q11.2 deletion in blood cells for somatic deletion mosaicism. We were able to study tissue samples from heart surgery from 23 patients, 9 of whom had 22q11 deletions by FISH analysis on metaphase spreads from peripheral lymphocytes. Analysis of 18 polymorphic markers from the 22q11.2 region in DNA prepared from thymus and/or heart vessels and/or conotruncus tissue and peripheral lymphocytes in each patient did not show any allelic loss. Thus somatic 22q11.2 deletions apparently do not play a major role in conotruncal heart defects in patients with or without germ line 22q11.2 deletion.
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Affiliation(s)
- Anita Rauch
- Institute of Human Genetics, Friedrich-Alexander University, Erlangen-Nuremberg, Germany.
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181
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Saitta SC, Harris SE, McDonald-McGinn DM, Emanuel BS, Tonnesen MK, Zackai EH, Seitz SC, Driscoll DA. Independent de novo 22q11.2 deletions in first cousins with DiGeorge/velocardiofacial syndrome. Am J Med Genet A 2004; 124A:313-7. [PMID: 14708107 PMCID: PMC2811370 DOI: 10.1002/ajmg.a.20421] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Deletions of chromosome 22q11.2 are found in the vast majority of patients with DiGeorge/velocardiofacial syndrome (DGS/VCFS). This most frequent microdeletion syndrome is estimated to occur in 1 in 4,000 live births. The majority of deletions are de novo, with 10% or less inherited from an affected parent. Here, we report two separate families with recurrence of a 22q11.2 deletion in first cousins. In each family, unaffected siblings (brother and sister) had an affected child. Fluorescence in situ hybridization (FISH) studies of the parents of each affected child were normal and hence, relatives were not considered at an increased risk for recurrence in another pregnancy. We used highly polymorphic microsatellite repeat markers from within 22q11.2 to determine the parental origin of each cousin's deletion and to assess whether parental germline mosaicism for the 22q11.2 deletion might be a factor in these cases. This analysis confirmed that in each case, the deletion occurred on a chromosome 22 derived from unrelated parents, consistent with independent de novo deletion events. Thus, we concluded that germline mosaicism as the underlying mechanism for affected cousins in these families was unlikely. Our findings underscore the high frequency with which the 22q11.2 deletion occurs in the general population and demonstrate the important role that PCR-based parental origin determination can have in recurrence risk counselling. Furthermore, relatives of affected individuals may benefit from genetic counselling and consider prenatal testing for the 22q11.2 deletion in future pregnancies, despite a low recurrence risk.
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Affiliation(s)
- Sulagna C. Saitta
- Division of Human Genetics and Molecular Biology, The Children’s Hospital of Philadelphia, Pennsylvania
- Department of Pediatrics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
| | - Stacy E. Harris
- Division of Human Genetics and Molecular Biology, The Children’s Hospital of Philadelphia, Pennsylvania
| | - Donna M. McDonald-McGinn
- Division of Human Genetics and Molecular Biology, The Children’s Hospital of Philadelphia, Pennsylvania
- Department of Pediatrics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
| | - Beverly S. Emanuel
- Division of Human Genetics and Molecular Biology, The Children’s Hospital of Philadelphia, Pennsylvania
- Department of Pediatrics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
| | - Melissa K. Tonnesen
- Division of Human Genetics and Molecular Biology, The Children’s Hospital of Philadelphia, Pennsylvania
| | - Elaine H. Zackai
- Division of Human Genetics and Molecular Biology, The Children’s Hospital of Philadelphia, Pennsylvania
- Department of Pediatrics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
- Department of Obstetrics and Gynecology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
| | | | - Deborah A. Driscoll
- Division of Human Genetics and Molecular Biology, The Children’s Hospital of Philadelphia, Pennsylvania
- Department of Obstetrics and Gynecology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
- Correspondence to: Deborah A. Driscoll, M.D., Division of Human Genetics and Molecular Biology, Abramson Research Center, Room 1002, The Children’s Hospital of Philadelphia, 3615 Civic Center Blvd, Philadelphia, PA 19104.
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182
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Erickson RP, Skinner S, Jacquet H, Campion D, Buckley PG, Mantripragada KK, Dumanski JP. Does chromosome 22 have anything to do with sex determination: further studies on a 46,XX,22q11.2 del male. Am J Med Genet A 2004; 123A:64-7. [PMID: 14556248 DOI: 10.1002/ajmg.a.20489] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Several years ago, we presented a patient with true hermaphroditism and partial duplication of chromosome 22 and no evidence of SRY (Aleck et al. [1999: Am J Med Genet 85:2-4]). Recently a 46,XX male with velocardiofacial syndrome and a deletion of 22q11.2 and no evidence of Y chromosomal loci in blood DNA was reported (Phelan et al. [2003: Am J Med Genet 116A:77-79]). We have restudied this patient as he enters puberty. Because chromosomal deletions sometimes involve micro rearrangements of nearby material, we have extensively studied this individual's chromosome 22 looking for evidence of any gene duplication. We studied a number of variable number tandem repeat (VNTR) loci along chromosome 22 in the patient and both parents. Normal Mendelian inheritance of the VNTRs was found. We then used quantitative multiplex PCR of short fluorescent fragments (QMPSF) to delineate the 22q11.2 deletion in this patient (Jacquet et al. [2002: Hum Molec Genet 11:2243-2249]) and found a pattern of deletion typical of the velocardiofacial DiGeorge syndrome. Finally, the patient's DNA has been analyzed using a full coverage human chromosome 22 genomic microarray (array comparative genomic hybridization [CGH]) for evidence of rearrangements outside the classical velocardiofacial DiGeorge associated deletion (Buckley et al. [2002: Hum Molec Genet 11:3221-3229]). The array-CGH profile of this patient confirms the deletion encompassing the typically deleted region associated with the velocardiofacial DiGeorge syndrome and provides no support for additional gene copy number aberrations on 22q. Thus, there is no evidence of any chromosome 22 trisomic material. In this case, the rare events of sex reversal and 22q11.2 deletion may have occurred together by chance.
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Affiliation(s)
- Robert P Erickson
- Steele Memorial Children's Research Center, Department of Pediatrics, University of Arizona College of Medicine, Tucson, Arizona 85724-5073, USA.
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183
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Briegel W, Cohen M. Das 22q11.2-Deletionssyndrom und seine Relevanz für die Kinder- und Jugendpsychiatrie. ZEITSCHRIFT FUR KINDER-UND JUGENDPSYCHIATRIE UND PSYCHOTHERAPIE 2004; 32:107-15. [PMID: 15181786 DOI: 10.1024/1422-4917.32.2.107] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Zusammenfassung: Das 22q11.2-Deletionssyndrom ist das häufigste bekannte Mikrodeletionssyndrom beim Menschen. Betroffene Patienten können eine Vielzahl körperlicher Störungen zeigen, vor allem charakteristische dysmorphe Gesichtszüge, Herzfehler, Thymus- sowie strukturelle oder funktionelle Gaumenanomalien. Typisch sind auch deutliche Beeinträchtigungen der motorischen, sprachlichen, kognitiven und sozialen Entwicklung sowie psychiatrische Störungen. Nach dem aktuellen Forschungsstand treten bei Kindern und Jugendlichen mit einer Deletion 22q11.2 insbesondere Aktivitäts- und Aufmerksamkeitsstörungen, affektive Störungen sowie tiefgreifende Entwicklungsstörungen gehäuft auf. 2% aller schizophrenen Erkrankungen im Erwachsenenalter sollen durch eine Deletion 22q11.2 verursacht sein. Der Artikel gibt einen aktuellen Überblick über Ätiologie, körperliche Symptomatik, Entwicklungsaspekte und psychiatrische Komorbidität des 22q11.2-Deletionssyndroms. Es werden klinische Kriterien für die humangenetische Abklärung einer Deletion 22q11.2 bei Kindern und Jugendlichen mit psychiatrischen Störungen definiert. Außerdem werden Behandlungsmöglichkeiten für die beim 22q11.2-Deletionssyndrom häufigen psychiatrischen Störungen erörtert. Insgesamt wird bei psychisch kranken Kindern und Jugendlichen eine Deletion 22q11.2 bisher noch zu selten diagnostiziert - trotz ihrer klinischen Relevanz.
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Affiliation(s)
- W Briegel
- Klinik für Kinder- und Jugendpsychiatrie und Psychotherapie, Bezirkskrankenhaus Landshut.
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184
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Hassed SJ, Hopcus-Niccum D, Zhang L, Li S, Mulvihill JJ. A new genomic duplication syndrome complementary to the velocardiofacial (22q11 deletion) syndrome. Clin Genet 2004; 65:400-4. [PMID: 15099348 DOI: 10.1111/j.0009-9163.2004.0212.x] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Fluorescence in situ hybridization (FISH) analysis can reveal undetected chromosomal rearrangements. We report a patient with cleft palate, hydronephrosis, and minor dysmorphic features, including low-set posteriorly rotated ears, down-slanting palpebral fissures, mandibular micrognathia, and brachymesophalangia. Routine chromosome analysis identified no abnormality of chromosome 22; FISH analysis with the TUPLE1 probe disclosed an interstitial duplication of 22q11.2. FISH analysis did not reveal the duplication on the initial testing of metaphase chromosomes, although, on review, the area was brighter on one chromosome in each metaphase spread. FISH analysis of interphase cells showed three TUPLE1-probe sites with two chromosome-specific identification probes in each cell. Family history showed two older full siblings, a brother with behavior problems, oppositional defiant disorder, and learning problems and a sister with hydronephrosis and mild delays. The father and both siblings had similar facial features, and all three had the same interstitial duplication of the TUPLE1 probe. This family illustrates the novel complementary duplication syndrome of the velocardiofacial syndrome, which adds it to the expanding list of genomic deletion/duplication syndromes. The laboratory results further show the utility and need for careful analysis of interphase cells even in samples where good quality metaphases are available.
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Affiliation(s)
- S J Hassed
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City 73104, USA.
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185
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Babcock M, Pavlicek A, Spiteri E, Kashork CD, Ioshikhes I, Shaffer LG, Jurka J, Morrow BE. Shuffling of genes within low-copy repeats on 22q11 (LCR22) by Alu-mediated recombination events during evolution. Genome Res 2004; 13:2519-32. [PMID: 14656960 PMCID: PMC403794 DOI: 10.1101/gr.1549503] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Low-copy repeats, or segmental duplications, are highly dynamic regions in the genome. The low-copy repeats on chromosome 22q11.2 (LCR22) are a complex mosaic of genes and pseudogenes formed by duplication processes; they mediate chromosome rearrangements associated with velo-cardio-facial syndrome/DiGeorge syndrome, der(22) syndrome, and cat-eye syndrome. The ability to trace the substrates and products of recombination events provides a unique opportunity to identify the mechanisms responsible for shaping LCR22s. We examined the genomic sequence of known LCR22 genes and their duplicated derivatives. We found Alu (SINE) elements at the breakpoints in the substrates and at the junctions in the truncated products of recombination for USP18, GGT, and GGTLA, consistent with Alu-mediated unequal crossing-over events. In addition, we were able to trace a likely interchromosomal Alu-mediated fusion between IGSF3 on 1p13.1 and GGT on 22q11.2. Breakpoints occurred inside Alu elements as well as in the 5' or 3' ends of them. A possible stimulus for the 5' or 3' terminal rearrangements may be the high sequence similarities between different Alu elements, combined with a potential recombinogenic role of retrotransposon target-site duplications flanking the Alu element, containing potentially kinkable DNA sites. Such sites may represent focal points for recombination. Thus, genome shuffling by Alu-mediated rearrangements has contributed to genome architecture during primate evolution.
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Affiliation(s)
- Melanie Babcock
- Department of Molecular Genetics, Albert Einstein College of Medicine, Bronx, New York, New York 10461, USA
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186
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Koolen DA, Veltman JA, Renier WO, Droog RP, van Kessel AG, de Vries BBA. Chromosome 22q11 deletion and pachygyria characterized by array-based comparative genomic hybridization. ACTA ACUST UNITED AC 2004; 131:322-4. [PMID: 15523606 DOI: 10.1002/ajmg.a.30377] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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187
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Saitta SC, Harris SE, Gaeth AP, Driscoll DA, McDonald-McGinn DM, Maisenbacher MK, Yersak JM, Chakraborty PK, Hacker AM, Zackai EH, Ashley T, Emanuel BS. Aberrant interchromosomal exchanges are the predominant cause of the 22q11.2 deletion. Hum Mol Genet 2003; 13:417-28. [PMID: 14681306 PMCID: PMC2836129 DOI: 10.1093/hmg/ddh041] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Chromosome 22q11.2 deletions are found in almost 90% of patients with DiGeorge/velocardiofacial syndrome (DGS/VCFS). Large, chromosome-specific low copy repeats (LCRs), flanking and within the deletion interval, are presumed to lead to misalignment and aberrant recombination in meiosis resulting in this frequent microdeletion syndrome. We traced the grandparental origin of regions flanking de novo 3 Mb deletions in 20 informative three-generation families. Haplotype reconstruction showed an unexpectedly high number of proximal interchromosomal exchanges between homologs, occurring in 19/20 families. Instead, the normal chromosome 22 in these probands showed interchromosomal exchanges in 2/15 informative meioses, a rate consistent with the genetic distance. Meiotic exchanges, visualized as MLH1 foci, localize to the distal long arm of chromosome 22 in 75% of human spermatocytes tested, also reflecting the genetic map. Additionally, we found no effect of proband gender or parental age on the crossover frequency. Parental origin studies in 65 de novo 3 Mb deletions (including these 20 patients) demonstrated no bias. Unlike Williams syndrome, we found no chromosomal inversions flanked by LCRs in 22 sets of parents of 22q11 deleted patients, or in eight non-deleted patients with a DGS/VCFS phenotype using FISH. Our data are consistent with significant aberrant interchromosomal exchange events during meiosis I in the proximal region of the affected chromosome 22 as the likely etiology for the deletion. This type of exchange occurs more often than is described for deletions of chromosomes 7q11, 15q11, 17p11 and 17q11, implying a difference in the meiotic behavior of chromosome 22.
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Affiliation(s)
- Sulagna C. Saitta
- Division of Human Genetics, The Children’s Hospital of Philadelphia, Philadelphia, PA, 19104 USA
- Department of Pediatrics, University of Pennsylvania School of Medicine, Philadelphia, PA, 19104 USA
| | - Stacy E. Harris
- Division of Human Genetics, The Children’s Hospital of Philadelphia, Philadelphia, PA, 19104 USA
| | - Ann P. Gaeth
- Department of Genetics, Yale University School of Medicine, New Haven, CT, 06520 USA
| | - Deborah A. Driscoll
- Division of Human Genetics, The Children’s Hospital of Philadelphia, Philadelphia, PA, 19104 USA
- Department of Pediatrics, University of Pennsylvania School of Medicine, Philadelphia, PA, 19104 USA
- Department of Obstetrics and Gynecology, University of Pennsylvania School of Medicine, Philadelphia, PA, 19104 USA
| | - Donna M. McDonald-McGinn
- Division of Human Genetics, The Children’s Hospital of Philadelphia, Philadelphia, PA, 19104 USA
| | - Melissa K. Maisenbacher
- Division of Human Genetics, The Children’s Hospital of Philadelphia, Philadelphia, PA, 19104 USA
| | - Jill M. Yersak
- Division of Human Genetics, The Children’s Hospital of Philadelphia, Philadelphia, PA, 19104 USA
| | - Prabir K. Chakraborty
- Department of Obstetrics and Gynecology, Uniformed Services University of the Health Sciences, Bethesda, MD, 20814, USA
| | - April M. Hacker
- Division of Human Genetics, The Children’s Hospital of Philadelphia, Philadelphia, PA, 19104 USA
| | - Elaine H. Zackai
- Division of Human Genetics, The Children’s Hospital of Philadelphia, Philadelphia, PA, 19104 USA
- Department of Pediatrics, University of Pennsylvania School of Medicine, Philadelphia, PA, 19104 USA
- Department of Obstetrics and Gynecology, University of Pennsylvania School of Medicine, Philadelphia, PA, 19104 USA
| | - Terry Ashley
- Department of Genetics, Yale University School of Medicine, New Haven, CT, 06520 USA
| | - Beverly S. Emanuel
- Division of Human Genetics, The Children’s Hospital of Philadelphia, Philadelphia, PA, 19104 USA
- Department of Pediatrics, University of Pennsylvania School of Medicine, Philadelphia, PA, 19104 USA
- To whom correspondence should be addressed at: Division of Human Genetics, The Children’s Hospital of Philadelphia, 3615 Civic Center Blvd, ARC 1002, Philadelphia, PA 19104, USA. Tel: +1 2155903856; Fax: +1 2155903764;
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188
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Bi W, Park SS, Shaw CJ, Withers MA, Patel PI, Lupski JR. Reciprocal crossovers and a positional preference for strand exchange in recombination events resulting in deletion or duplication of chromosome 17p11.2. Am J Hum Genet 2003; 73:1302-15. [PMID: 14639526 PMCID: PMC1180396 DOI: 10.1086/379979] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2003] [Accepted: 09/16/2003] [Indexed: 01/15/2023] Open
Abstract
Smith-Magenis syndrome (SMS) is caused by an approximately 4-Mb heterozygous interstitial deletion on chromosome 17p11.2 in approximately 80%-90% of affected patients. Three large ( approximately 200 kb), complex, and highly homologous ( approximately 98%) low-copy repeats (LCRs) are located inside or flanking the SMS common deletion. These repeats, also known as "SMS-REPs," are termed "distal," "middle," and "proximal." The directly oriented distal and proximal copies act as substrates for nonallelic homologous recombination resulting in both the deletion associated with SMS and the reciprocal duplication: dup(17)(p11.2p11.2). Using restriction enzyme cis-morphism analyses and direct sequencing, we mapped the regions of strand exchange in 16 somatic-cell hybrids that harbor only the recombinant SMS-REP. Our studies showed that the sites of crossovers were distributed throughout the region of homology between the distal and proximal SMS-REPs. However, despite approximately 170 kb of high homology, 50% of the recombinant junctions occurred in a 12.0-kb region within the KER gene clusters. DNA sequencing of this hotspot (positional preference for strand exchange) in seven recombinant SMS-REPs narrowed the crossovers to an approximately 8-kb interval. Four of them occurred in a 1,655-bp region rich in polymorphic nucleotides that could potentially reflect frequent gene conversion. For further evaluation of the strand exchange frequency in patients with SMS, novel junction fragments from the recombinant SMS-REPs were identified. As predicted by the reciprocal-recombination model, junction fragments were also identified from this hotspot region in patients with dup(17)(p11.2p11.2), documenting reciprocity of the positional preference for strand exchange. Several potential cis-acting recombination-promoting sequences were identified within the hotspot. It is interesting that we found 2.1-kb AT-rich inverted repeats flanking the proximal and middle KER gene clusters but not the distal one. The role of any or all of these in stimulating double-strand breaks around this positional recombination hotspot remains to be explored.
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Affiliation(s)
- Weimin Bi
- Departments of Molecular and Human Genetics, Neurology, and Pediatrics, Baylor College of Medicine, and Texas Children’s Hospital, Houston
| | - Sung-Sup Park
- Departments of Molecular and Human Genetics, Neurology, and Pediatrics, Baylor College of Medicine, and Texas Children’s Hospital, Houston
| | - Christine J. Shaw
- Departments of Molecular and Human Genetics, Neurology, and Pediatrics, Baylor College of Medicine, and Texas Children’s Hospital, Houston
| | - Marjorie A. Withers
- Departments of Molecular and Human Genetics, Neurology, and Pediatrics, Baylor College of Medicine, and Texas Children’s Hospital, Houston
| | - Pragna I. Patel
- Departments of Molecular and Human Genetics, Neurology, and Pediatrics, Baylor College of Medicine, and Texas Children’s Hospital, Houston
| | - James R. Lupski
- Departments of Molecular and Human Genetics, Neurology, and Pediatrics, Baylor College of Medicine, and Texas Children’s Hospital, Houston
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189
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Ensenauer RE, Adeyinka A, Flynn HC, Michels VV, Lindor NM, Dawson DB, Thorland EC, Lorentz CP, Goldstein JL, McDonald MT, Smith WE, Simon-Fayard E, Alexander AA, Kulharya AS, Ketterling RP, Clark RD, Jalal SM. Microduplication 22q11.2, an emerging syndrome: clinical, cytogenetic, and molecular analysis of thirteen patients. Am J Hum Genet 2003; 73:1027-40. [PMID: 14526392 PMCID: PMC1180483 DOI: 10.1086/378818] [Citation(s) in RCA: 253] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2003] [Accepted: 07/29/2003] [Indexed: 11/03/2022] Open
Abstract
Chromosome 22, particularly band 22q11.2, is predisposed to rearrangements due to misalignments of low-copy repeats (LCRs). DiGeorge/velocardiofacial syndrome (DG/VCFS) is a common disorder resulting from microdeletion within the same band. Although both deletion and duplication are expected to occur in equal proportions as reciprocal events caused by LCR-mediated rearrangements, very few microduplications have been identified. We have identified 13 cases of microduplication 22q11.2, primarily by interphase fluorescence in situ hybridization (FISH). The size of the duplications, determined by FISH probes from bacterial artificial chromosomes and P(1) artificial chromosomes, range from 3-4 Mb to 6 Mb, and the exchange points seem to involve an LCR. Molecular analysis based on 15 short tandem repeats confirmed the size of the duplications and indicated that at least 1 of 15 loci has three alleles present. The patients' phenotypes ranged from mild to severe, sharing a tendency for velopharyngeal insufficiency with DG/VCFS but having other distinctive characteristics, as well. Although the present series of patients was ascertained because of some overlapping features with DG/VCF syndromes, the microduplication of 22q11.2 appears to be a new syndrome.
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Affiliation(s)
- Regina E. Ensenauer
- Department of Medical Genetics, and Cytogenetics Laboratory and Molecular Genetics Laboratory, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN; Department of Pediatrics, Duke University Medical Center, Durham, NC; Division of Genetics, Barbara Bush Children’s Hospital, Maine Medical Center, Portland, ME; Department of Pediatrics, Division of Neonatology, Loma Linda University Medical Center, and Division of Genetics, Loma Linda University Children’s Hospital, Loma Linda, CA; Desert Pediatrics, Inc., Palm Desert, CA; and Department of Pediatrics and Pathology, Medical College of Georgia, Augusta, GA
| | - Adewale Adeyinka
- Department of Medical Genetics, and Cytogenetics Laboratory and Molecular Genetics Laboratory, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN; Department of Pediatrics, Duke University Medical Center, Durham, NC; Division of Genetics, Barbara Bush Children’s Hospital, Maine Medical Center, Portland, ME; Department of Pediatrics, Division of Neonatology, Loma Linda University Medical Center, and Division of Genetics, Loma Linda University Children’s Hospital, Loma Linda, CA; Desert Pediatrics, Inc., Palm Desert, CA; and Department of Pediatrics and Pathology, Medical College of Georgia, Augusta, GA
| | - Heather C. Flynn
- Department of Medical Genetics, and Cytogenetics Laboratory and Molecular Genetics Laboratory, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN; Department of Pediatrics, Duke University Medical Center, Durham, NC; Division of Genetics, Barbara Bush Children’s Hospital, Maine Medical Center, Portland, ME; Department of Pediatrics, Division of Neonatology, Loma Linda University Medical Center, and Division of Genetics, Loma Linda University Children’s Hospital, Loma Linda, CA; Desert Pediatrics, Inc., Palm Desert, CA; and Department of Pediatrics and Pathology, Medical College of Georgia, Augusta, GA
| | - Virginia V. Michels
- Department of Medical Genetics, and Cytogenetics Laboratory and Molecular Genetics Laboratory, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN; Department of Pediatrics, Duke University Medical Center, Durham, NC; Division of Genetics, Barbara Bush Children’s Hospital, Maine Medical Center, Portland, ME; Department of Pediatrics, Division of Neonatology, Loma Linda University Medical Center, and Division of Genetics, Loma Linda University Children’s Hospital, Loma Linda, CA; Desert Pediatrics, Inc., Palm Desert, CA; and Department of Pediatrics and Pathology, Medical College of Georgia, Augusta, GA
| | - Noralane M. Lindor
- Department of Medical Genetics, and Cytogenetics Laboratory and Molecular Genetics Laboratory, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN; Department of Pediatrics, Duke University Medical Center, Durham, NC; Division of Genetics, Barbara Bush Children’s Hospital, Maine Medical Center, Portland, ME; Department of Pediatrics, Division of Neonatology, Loma Linda University Medical Center, and Division of Genetics, Loma Linda University Children’s Hospital, Loma Linda, CA; Desert Pediatrics, Inc., Palm Desert, CA; and Department of Pediatrics and Pathology, Medical College of Georgia, Augusta, GA
| | - D. Brian Dawson
- Department of Medical Genetics, and Cytogenetics Laboratory and Molecular Genetics Laboratory, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN; Department of Pediatrics, Duke University Medical Center, Durham, NC; Division of Genetics, Barbara Bush Children’s Hospital, Maine Medical Center, Portland, ME; Department of Pediatrics, Division of Neonatology, Loma Linda University Medical Center, and Division of Genetics, Loma Linda University Children’s Hospital, Loma Linda, CA; Desert Pediatrics, Inc., Palm Desert, CA; and Department of Pediatrics and Pathology, Medical College of Georgia, Augusta, GA
| | - Erik C. Thorland
- Department of Medical Genetics, and Cytogenetics Laboratory and Molecular Genetics Laboratory, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN; Department of Pediatrics, Duke University Medical Center, Durham, NC; Division of Genetics, Barbara Bush Children’s Hospital, Maine Medical Center, Portland, ME; Department of Pediatrics, Division of Neonatology, Loma Linda University Medical Center, and Division of Genetics, Loma Linda University Children’s Hospital, Loma Linda, CA; Desert Pediatrics, Inc., Palm Desert, CA; and Department of Pediatrics and Pathology, Medical College of Georgia, Augusta, GA
| | - Cindy Pham Lorentz
- Department of Medical Genetics, and Cytogenetics Laboratory and Molecular Genetics Laboratory, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN; Department of Pediatrics, Duke University Medical Center, Durham, NC; Division of Genetics, Barbara Bush Children’s Hospital, Maine Medical Center, Portland, ME; Department of Pediatrics, Division of Neonatology, Loma Linda University Medical Center, and Division of Genetics, Loma Linda University Children’s Hospital, Loma Linda, CA; Desert Pediatrics, Inc., Palm Desert, CA; and Department of Pediatrics and Pathology, Medical College of Georgia, Augusta, GA
| | - Jennifer L. Goldstein
- Department of Medical Genetics, and Cytogenetics Laboratory and Molecular Genetics Laboratory, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN; Department of Pediatrics, Duke University Medical Center, Durham, NC; Division of Genetics, Barbara Bush Children’s Hospital, Maine Medical Center, Portland, ME; Department of Pediatrics, Division of Neonatology, Loma Linda University Medical Center, and Division of Genetics, Loma Linda University Children’s Hospital, Loma Linda, CA; Desert Pediatrics, Inc., Palm Desert, CA; and Department of Pediatrics and Pathology, Medical College of Georgia, Augusta, GA
| | - Marie T. McDonald
- Department of Medical Genetics, and Cytogenetics Laboratory and Molecular Genetics Laboratory, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN; Department of Pediatrics, Duke University Medical Center, Durham, NC; Division of Genetics, Barbara Bush Children’s Hospital, Maine Medical Center, Portland, ME; Department of Pediatrics, Division of Neonatology, Loma Linda University Medical Center, and Division of Genetics, Loma Linda University Children’s Hospital, Loma Linda, CA; Desert Pediatrics, Inc., Palm Desert, CA; and Department of Pediatrics and Pathology, Medical College of Georgia, Augusta, GA
| | - Wendy E. Smith
- Department of Medical Genetics, and Cytogenetics Laboratory and Molecular Genetics Laboratory, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN; Department of Pediatrics, Duke University Medical Center, Durham, NC; Division of Genetics, Barbara Bush Children’s Hospital, Maine Medical Center, Portland, ME; Department of Pediatrics, Division of Neonatology, Loma Linda University Medical Center, and Division of Genetics, Loma Linda University Children’s Hospital, Loma Linda, CA; Desert Pediatrics, Inc., Palm Desert, CA; and Department of Pediatrics and Pathology, Medical College of Georgia, Augusta, GA
| | - Elba Simon-Fayard
- Department of Medical Genetics, and Cytogenetics Laboratory and Molecular Genetics Laboratory, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN; Department of Pediatrics, Duke University Medical Center, Durham, NC; Division of Genetics, Barbara Bush Children’s Hospital, Maine Medical Center, Portland, ME; Department of Pediatrics, Division of Neonatology, Loma Linda University Medical Center, and Division of Genetics, Loma Linda University Children’s Hospital, Loma Linda, CA; Desert Pediatrics, Inc., Palm Desert, CA; and Department of Pediatrics and Pathology, Medical College of Georgia, Augusta, GA
| | - Alan A. Alexander
- Department of Medical Genetics, and Cytogenetics Laboratory and Molecular Genetics Laboratory, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN; Department of Pediatrics, Duke University Medical Center, Durham, NC; Division of Genetics, Barbara Bush Children’s Hospital, Maine Medical Center, Portland, ME; Department of Pediatrics, Division of Neonatology, Loma Linda University Medical Center, and Division of Genetics, Loma Linda University Children’s Hospital, Loma Linda, CA; Desert Pediatrics, Inc., Palm Desert, CA; and Department of Pediatrics and Pathology, Medical College of Georgia, Augusta, GA
| | - Anita S. Kulharya
- Department of Medical Genetics, and Cytogenetics Laboratory and Molecular Genetics Laboratory, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN; Department of Pediatrics, Duke University Medical Center, Durham, NC; Division of Genetics, Barbara Bush Children’s Hospital, Maine Medical Center, Portland, ME; Department of Pediatrics, Division of Neonatology, Loma Linda University Medical Center, and Division of Genetics, Loma Linda University Children’s Hospital, Loma Linda, CA; Desert Pediatrics, Inc., Palm Desert, CA; and Department of Pediatrics and Pathology, Medical College of Georgia, Augusta, GA
| | - Rhett P. Ketterling
- Department of Medical Genetics, and Cytogenetics Laboratory and Molecular Genetics Laboratory, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN; Department of Pediatrics, Duke University Medical Center, Durham, NC; Division of Genetics, Barbara Bush Children’s Hospital, Maine Medical Center, Portland, ME; Department of Pediatrics, Division of Neonatology, Loma Linda University Medical Center, and Division of Genetics, Loma Linda University Children’s Hospital, Loma Linda, CA; Desert Pediatrics, Inc., Palm Desert, CA; and Department of Pediatrics and Pathology, Medical College of Georgia, Augusta, GA
| | - Robin D. Clark
- Department of Medical Genetics, and Cytogenetics Laboratory and Molecular Genetics Laboratory, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN; Department of Pediatrics, Duke University Medical Center, Durham, NC; Division of Genetics, Barbara Bush Children’s Hospital, Maine Medical Center, Portland, ME; Department of Pediatrics, Division of Neonatology, Loma Linda University Medical Center, and Division of Genetics, Loma Linda University Children’s Hospital, Loma Linda, CA; Desert Pediatrics, Inc., Palm Desert, CA; and Department of Pediatrics and Pathology, Medical College of Georgia, Augusta, GA
| | - Syed M. Jalal
- Department of Medical Genetics, and Cytogenetics Laboratory and Molecular Genetics Laboratory, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN; Department of Pediatrics, Duke University Medical Center, Durham, NC; Division of Genetics, Barbara Bush Children’s Hospital, Maine Medical Center, Portland, ME; Department of Pediatrics, Division of Neonatology, Loma Linda University Medical Center, and Division of Genetics, Loma Linda University Children’s Hospital, Loma Linda, CA; Desert Pediatrics, Inc., Palm Desert, CA; and Department of Pediatrics and Pathology, Medical College of Georgia, Augusta, GA
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190
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Spiteri E, Babcock M, Kashork CD, Wakui K, Gogineni S, Lewis DA, Williams KM, Minoshima S, Sasaki T, Shimizu N, Potocki L, Pulijaal V, Shanske A, Shaffer LG, Morrow BE. Frequent translocations occur between low copy repeats on chromosome 22q11.2 (LCR22s) and telomeric bands of partner chromosomes. Hum Mol Genet 2003; 12:1823-37. [PMID: 12874103 DOI: 10.1093/hmg/ddg203] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The chromosome 22q11.2 region is susceptible to rearrangements, mediated by low copy repeats (LCR22s). Deletions and duplications are mediated by homologous recombination events between LCR22s. The recurrent balanced constitutional translocation t(11;22)(q23;q11) breakpoint occurs in an LCR22 and is mediated by double strand breaks in AT-rich palindromes on both chromosomes 11 and 22. Recently, two cases of a t(17;22)(q11;q11) were reported, mediated by a similar mechanism (21). Except for these constitutional translocations, the molecular basis for non-recurrent, reciprocal 22q11.2 translocations is not known. To determine whether there are specific mechanisms that could mediate translocations, we analyzed cell lines derived from 14 different individuals by genotyping and FISH mapping. Somatic cell hybrid analysis was carried out for four cell lines. In five cell lines, the translocation breakpoints occurred in the same LCR22 as for the t(11;22) translocation, suggesting that similar molecular mechanisms are responsible. An additional three occurred in other LCR22s, and six were in non-LCR22 regions, mostly in the proximal half of the 22q11.2 region. The translocation breakpoints on the partner chromosomes were all located in the telomeric bands, proximal to the most telomeric unique sequence probe, in eight cell lines and distal to those loci in six. Therefore, several of the breakpoints were found to occur in the vicinity of highly dynamic regions of the genome, 22q11.2 and telomeric bands. We hypothesize that these regions are more susceptible to breakage and repair, resulting in translocations.
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Affiliation(s)
- Elizabeth Spiteri
- Department of Molecular Genetics, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
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191
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Shiohama A, Sasaki T, Noda S, Minoshima S, Shimizu N. Molecular cloning and expression analysis of a novel gene DGCR8 located in the DiGeorge syndrome chromosomal region. Biochem Biophys Res Commun 2003; 304:184-90. [PMID: 12705904 DOI: 10.1016/s0006-291x(03)00554-0] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We have identified and cloned a novel gene (DGCR8) from the human chromosome 22q11.2. This gene is located in the DiGeorge syndrome chromosomal region (DGCR). It consists of 14 exons spanning over 35kb and produces transcripts with ORF of 2322bp, encoding a protein of 773 amino acids. We also isolated a mouse ortholog Dgcr8 and found it has 95.3% identity with human DGCR8 at the amino acid sequence level. Northern blot analysis of human and mouse tissues from adult and fetus showed rather ubiquitous expression. However, the in situ hybridization of mouse embryos revealed that mouse Dgcr8 transcripts are localized in neuroepithelium of primary brain, limb bud, vessels, thymus, and around the palate during the developmental stages of embryos. The expression profile of Dgcr8 in developing mouse embryos is consistent with the clinical phenotypes including congenital heart defects and palate clefts associated with DiGeorge syndrome (DGS)/conotruncal anomaly face syndrome (CAFS)/velocardiofacial syndrome (VCFS), which are caused by monoallelic microdeletion of chromosome 22q11.2.
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Affiliation(s)
- Aiko Shiohama
- Department of Molecular Biology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, 160-8582, Tokyo, Japan
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192
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Gebhardt GS, Devriendt K, Thoelen R, Swillen A, Pijkels E, Fryns JP, Vermeesch JR, Gewillig M. No evidence for a parental inversion polymorphism predisposing to rearrangements at 22q11.2 in the DiGeorge/Velocardiofacial syndrome. Eur J Hum Genet 2003; 11:109-11. [PMID: 12634857 DOI: 10.1038/sj.ejhg.5200930] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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193
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Abstract
Genomic rearrangements play a major role in the pathogenesis of human genetic diseases. Nonallelic homologous recombination (NAHR) between low-copy repeats (LCRs) that flank unique genomic segments results in changes of genome organization and can cause a loss or gain of genomic segments. These LCRs appear to have arisen recently during primate speciation via paralogous segmental duplication, thus making the human species particularly susceptible to genomic rearrangements. Genomic disorders are defined as a group of diseases that result from genomic rearrangements, mostly mediated by NAHR. Molecular investigations of genomic disorders have revealed genome architectural features associated with susceptibility to rearrangements and the recombination mechanisms responsible for such rearrangements. The human genome sequence project reveals that LCRs may account for 5% of the genome, suggesting that many novel genomic disorders might still remain to be recognized.
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Affiliation(s)
- Ken Inoue
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA.
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194
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Shaw CJ, Bi W, Lupski JR. Genetic proof of unequal meiotic crossovers in reciprocal deletion and duplication of 17p11.2. Am J Hum Genet 2002; 71:1072-81. [PMID: 12375235 PMCID: PMC420000 DOI: 10.1086/344346] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2002] [Accepted: 08/14/2002] [Indexed: 12/11/2022] Open
Abstract
A number of common contiguous gene syndromes have been shown to result from nonallelic homologous recombination (NAHR) within region-specific low-copy repeats (LCRs). The reciprocal duplications are predicted to occur at the same frequency; however, probably because of ascertainment bias and milder phenotypes, reciprocal events have been identified in only a few cases to date. We previously described seven patients with dup(17)(p11.2p11.2), the reciprocal of the Smith-Magenis syndrome (SMS) deletion, del(17)(p11.2p11.2). In >90% of patients with SMS, identical approximately 3.7-Mb deletions in 17p11.2 have been identified. These deletions are flanked by large (approximately 200 kb), highly homologous, directly oriented LCRs (i.e., proximal and distal SMS repeats [SMS-REPs]). The third (middle) SMS-REP is inverted with respect to them and maps inside the commonly deleted genomic region. To investigate the parental origin and to determine whether the common deletion and duplication arise by unequal crossovers mediated through NAHR between the proximal and distal SMS-REPs, we analyzed the haplotypes of 14 families with SMS and six families with dup(17)(p11.2p11.2), using microsatellite markers directly flanking the SMS common deletion breakpoints. Our data indicate that reciprocal deletion and duplication of 17p11.2 result from unequal meiotic crossovers. These rearrangements occur via both interchromosomal and intrachromosomal exchange events between the proximal and distal SMS-REPs, and there appears to be no parental-origin bias associated with common SMS deletions and the reciprocal duplications.
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Affiliation(s)
- Christine J. Shaw
- Departments of Molecular and Human Genetics and Pediatrics, Baylor College of Medicine, and Texas Children's Hospital, Houston
| | - Weimin Bi
- Departments of Molecular and Human Genetics and Pediatrics, Baylor College of Medicine, and Texas Children's Hospital, Houston
| | - James R. Lupski
- Departments of Molecular and Human Genetics and Pediatrics, Baylor College of Medicine, and Texas Children's Hospital, Houston
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195
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Debeer P, Mols R, Huysmans C, Devriendt K, Van de Ven WJM, Fryns JP. Involvement of a palindromic chromosome 22-specific low-copy repeat in a constitutional t(X; 22)(q27;q11). Clin Genet 2002; 62:410-4. [PMID: 12431258 DOI: 10.1034/j.1399-0004.2002.620510.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Segmental duplications or low-copy repeats (LCRs) on chromosome 22q11 have been implicated in several chromosomal rearrangements. The presence of AT-rich regions in these duplications may lead to the formation of hairpin structures, which facilitate chromosomal rearrangement. Here we report the involvement of such a low-copy repeat in a t(X;22) associated with a neural tube defect. Molecular analysis of the chromosomal breakpoints revealed that the chromosome 22 breakpoint maps in the palindromic non-AT-rich NF1-like region of low-copy repeat B (LCR-B). No palindromic region was encountered near the breakpoint on chromosome X. Our findings confirm that there is no single mechanism leading to translocations with chromosome 22q11 involvement. Because LCR-B does not contain genes involved in neural tube development, we believe that the gene responsible for the observed phenotype is most likely localized on chromosome X.
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Affiliation(s)
- P Debeer
- Laboratory for Molecular Oncology and Center for Human Genetics, Herestraat 49, B-3000 Leuven, Belgium
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196
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Bailey JA, Gu Z, Clark RA, Reinert K, Samonte RV, Schwartz S, Adams MD, Myers EW, Li PW, Eichler EE. Recent segmental duplications in the human genome. Science 2002; 297:1003-7. [PMID: 12169732 DOI: 10.1126/science.1072047] [Citation(s) in RCA: 957] [Impact Index Per Article: 43.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Primate-specific segmental duplications are considered important in human disease and evolution. The inability to distinguish between allelic and duplication sequence overlap has hampered their characterization as well as assembly and annotation of our genome. We developed a method whereby each public sequence is analyzed at the clone level for overrepresentation within a whole-genome shotgun sequence. This test has the ability to detect duplications larger than 15 kilobases irrespective of copy number, location, or high sequence similarity. We mapped 169 large regions flanked by highly similar duplications. Twenty-four of these hot spots of genomic instability have been associated with genetic disease. Our analysis indicates a highly nonrandom chromosomal and genic distribution of recent segmental duplications, with a likely role in expanding protein diversity.
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Affiliation(s)
- Jeffrey A Bailey
- Department of Genetics, Center for Computational Genomics, and Center for Human Genetics, Case Western Reserve University School of Medicine and University Hospitals of Cleveland, Cleveland, OH 44106, USA
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197
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Sullivan KE. Immunologic issues in VCFS/chromosome 22q11.2 deletion syndrome. PROGRESS IN PEDIATRIC CARDIOLOGY 2002. [DOI: 10.1016/s1058-9813(02)00034-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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198
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Maynard TM, Haskell GT, Lieberman JA, LaMantia AS. 22q11 DS: genomic mechanisms and gene function in DiGeorge/velocardiofacial syndrome. Int J Dev Neurosci 2002; 20:407-19. [PMID: 12175881 DOI: 10.1016/s0736-5748(02)00050-3] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
Abstract
22q11 deletion syndrome (22qDS), also known as DiGeorge or velocardiofacial syndrome (DGS/VCFS), is a relatively common genetic anomaly that results in malformations of the heart, face and limbs. In addition, patients with 22qDS are at significant risk for psychiatric disorders as well, with one in four developing schizophrenia, and one in six developing major depressive disorders. Like several other deletion syndromes associated with psychiatric or cognitive problems, it has been difficult to determine which of the specific genes in this genomic region may mediate the syndrome. For example, patients with different genomic deletions within the 22q11 region have been found that have similar phenotypes, even though their deletions do not compromise the same set of genes. In this review, we discuss the individual genes found in the region of 22q11 that is commonly deleted in 22qDS patients, and the potential roles each of these genes may play in the syndrome. Although many of these genes are interesting candidates by themselves, we hypothesize that the full spectrum of anomalies associated with 22qDS may result from the combined result of disruptions to numerous genes within the region that are involved in similar developmental or cellular processes.
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Affiliation(s)
- Thomas M Maynard
- Department of Cell and Molecular Physiology, CB #7545, UNC School of Medicine, University of North Carolina, Chapel Hill, NC 27599, USA
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199
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McDermid HE, Morrow BE. Genomic disorders on 22q11. Am J Hum Genet 2002; 70:1077-88. [PMID: 11925570 PMCID: PMC447586 DOI: 10.1086/340363] [Citation(s) in RCA: 195] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2002] [Accepted: 02/18/2002] [Indexed: 11/03/2022] Open
Abstract
The 22q11 region is involved in chromosomal rearrangements that lead to altered gene dosage, resulting in genomic disorders that are characterized by mental retardation and/or congenital malformations. Three such disorders-cat-eye syndrome (CES), der(22) syndrome, and velocardiofacial syndrome/DiGeorge syndrome (VCFS/DGS)-are associated with four, three, and one dose, respectively, of parts of 22q11. The critical region for CES lies centromeric to the deletion region of VCFS/DGS, although, in some cases, the extra material in CES extends across the VCFS/DGS region. The der(22) syndrome region overlaps both the CES region and the VCFS/DGS region. Molecular approaches have revealed a set of common chromosome breakpoints that are shared between the three disorders, implicating specific mechanisms that cause these rearrangements. Most VCFS/DGS and CES rearrangements are likely to occur by homologous recombination events between blocks of low-copy repeats (e.g., LCR22), whereas nonhomologous recombination mechanisms lead to the constitutional t(11;22) translocation. Meiotic nondisjunction events in carriers of the t(11;22) translocation can then lead to offspring with der(22) syndrome. The molecular basis of the clinical phenotype of these genomic disorders has also begun to be addressed. Analysis of both the genomic sequence for the 22q11 interval and the orthologous regions in the mouse has identified >24 genes that are shared between VCFS/DGS and der(22) syndrome and has identified 14 putative genes that are shared between CES and der(22) syndrome. The ability to manipulate the mouse genome aids in the identification of candidate genes in these three syndromes. Research on genomic disorders on 22q11 will continue to expand our knowledge of the mechanisms of chromosomal rearrangements and the molecular basis of their phenotypic consequences.
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Affiliation(s)
- Heather E. McDermid
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta; and Department of Molecular Genetics, Albert Einstein College of Medicine, Bronx, NY
| | - Bernice E. Morrow
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta; and Department of Molecular Genetics, Albert Einstein College of Medicine, Bronx, NY
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200
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Bailey JA, Yavor AM, Viggiano L, Misceo D, Horvath JE, Archidiacono N, Schwartz S, Rocchi M, Eichler EE. Human-specific duplication and mosaic transcripts: the recent paralogous structure of chromosome 22. Am J Hum Genet 2002; 70:83-100. [PMID: 11731936 PMCID: PMC419985 DOI: 10.1086/338458] [Citation(s) in RCA: 133] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2001] [Accepted: 10/31/2001] [Indexed: 11/03/2022] Open
Abstract
In recent decades, comparative chromosomal banding, chromosome painting, and gene-order studies have shown strong conservation of gross chromosome structure and gene order in mammals. However, findings from the human genome sequence suggest an unprecedented degree of recent (<35 million years ago) segmental duplication. This dynamism of segmental duplications has important implications in disease and evolution. Here we present a chromosome-wide view of the structure and evolution of the most highly homologous duplications (> or = 1 kb and > or = 90%) on chromosome 22. Overall, 10.8% (3.7/33.8 Mb) of chromosome 22 is duplicated, with an average sequence identity of 95.4%. To organize the duplications into tractable units, intron-exon structure and well-defined duplication boundaries were used to define 78 duplicated modules (minimally shared evolutionary segments) with 157 copies on chromosome 22. Analysis of these modules provides evidence for the creation or modification of 11 novel transcripts. Comparative FISH analyses of human, chimpanzee, gorilla, orangutan, and macaque reveal qualitative and quantitative differences in the distribution of these duplications--consistent with their recent origin. Several duplications appear to be human specific, including a approximately 400-kb duplication (99.4%-99.8% sequence identity) that transposed from chromosome 14 to the most proximal pericentromeric region of chromosome 22. Experimental and in silico data further support a pericentromeric gradient of duplications where the most recent duplications transpose adjacent to the centromere. Taken together, these data suggest that segmental duplications have been an ongoing process of primate genome evolution, contributing to recent gene innovation and the dynamic transformation of genome architecture within and among closely related species.
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MESH Headings
- Animals
- Centromere/genetics
- Chromosomes, Human, Pair 14/genetics
- Chromosomes, Human, Pair 22/genetics
- Evolution, Molecular
- Exons/genetics
- Gene Dosage
- Gene Duplication
- Genes, Duplicate/genetics
- Humans
- In Situ Hybridization, Fluorescence
- Introns/genetics
- Mosaicism/genetics
- Primates/genetics
- RNA, Messenger/analysis
- RNA, Messenger/genetics
- Species Specificity
- Time Factors
- Transcription, Genetic/genetics
- Translocation, Genetic/genetics
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Affiliation(s)
- Jeffrey A Bailey
- Department of Genetics and Center for Human Genetics, Case Western Reserve University School of Medicine and University Hospitals of Cleveland, OH, USA
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