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Ballif BC, Theisen A, Coppinger J, Gowans GC, Hersh JH, Madan-Khetarpal S, Schmidt KR, Tervo R, Escobar LF, Friedrich CA, McDonald M, Campbell L, Ming JE, Zackai EH, Bejjani BA, Shaffer LG. Expanding the clinical phenotype of the 3q29 microdeletion syndrome and characterization of the reciprocal microduplication. Mol Cytogenet 2008; 1:8. [PMID: 18471269 PMCID: PMC2408925 DOI: 10.1186/1755-8166-1-8] [Citation(s) in RCA: 176] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2008] [Accepted: 04/28/2008] [Indexed: 11/11/2022] Open
Abstract
Background Interstitial deletions of 3q29 have been recently described as a microdeletion syndrome mediated by nonallelic homologous recombination between low-copy repeats resulting in an ~1.6 Mb common-sized deletion. Given the molecular mechanism causing the deletion, the reciprocal duplication is anticipated to occur with equal frequency, although only one family with this duplication has been reported. Results In this study we describe 14 individuals with microdeletions of 3q29, including one family with a mildly affected mother and two affected children, identified among 14,698 individuals with idiopathic mental retardation who were analyzed by array CGH. Eleven individuals had typical 1.6-Mb deletions. Three individuals had deletions that flank, span, or partially overlap the commonly deleted region. Although the clinical presentations of individuals with typical-sized deletions varied, several features were present in multiple individuals, including mental retardation and microcephaly. We also identified 19 individuals with duplications of 3q29, five of which appear to be the reciprocal duplication product of the 3q29 microdeletion and 14 of which flank, span, or partially overlap the common deletion region. The clinical features of individuals with microduplications of 3q29 also varied with few common features. De novo and inherited abnormalities were found in both the microdeletion and microduplication cohorts illustrating the need for parental samples to fully characterize these abnormalities. Conclusion Our report demonstrates that array CGH is especially suited to identify chromosome abnormalities with unclear or variable presentations.
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Yurov YB, Liehr T, Shaffer LG, Iourov IY, Vorsanova SG. A new open access journal for a rapidly evolving biomedical field: introducing Molecular Cytogenetics. Mol Cytogenet 2008; 1:1. [PMID: 18471306 PMCID: PMC2367691 DOI: 10.1186/1755-8166-1-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2007] [Accepted: 03/26/2008] [Indexed: 11/24/2022] Open
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128
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Jiang YH, Wauki K, Liu Q, Bressler J, Pan Y, Kashork CD, Shaffer LG, Beaudet AL. Genomic analysis of the chromosome 15q11-q13 Prader-Willi syndrome region and characterization of transcripts for GOLGA8E and WHCD1L1 from the proximal breakpoint region. BMC Genomics 2008; 9:50. [PMID: 18226259 PMCID: PMC2268926 DOI: 10.1186/1471-2164-9-50] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2007] [Accepted: 01/28/2008] [Indexed: 01/02/2023] Open
Abstract
BACKGROUND Prader-Willi syndrome (PWS) is a neurobehavioral disorder characterized by neonatal hypotonia, childhood obesity, dysmorphic features, hypogonadism, mental retardation, and behavioral problems. Although PWS is most often caused by a paternal interstitial deletion of a 6-Mb region of chromosome 15q11-q13, the identity of the exact protein coding or noncoding RNAs whose deficiency produces the PWS phenotype is uncertain. There are also reports describing a PWS-like phenotype in a subset of patients with full mutations in the FMR1 (fragile X mental retardation 1) gene. Taking advantage of the human genome sequence, we have performed extensive sequence analysis and molecular studies for the PWS candidate region. RESULTS We have characterized transcripts for the first time for two UCSC Genome Browser predicted protein-coding genes, GOLGA8E (golgin subfamily a, 8E) and WHDC1L1 (WAS protein homology region containing 1-like 1) and have further characterized two previously reported genes, CYF1P1 and NIPA2; all four genes are in the region close to the proximal/centromeric deletion breakpoint (BP1). GOLGA8E belongs to the golgin subfamily of coiled-coil proteins associated with the Golgi apparatus. Six out of 16 golgin subfamily proteins in the human genome have been mapped in the chromosome 15q11-q13 and 15q24-q26 regions. We have also identified more than 38 copies of GOLGA8E-like sequence in the 15q11-q14 and 15q23-q26 regions which supports the presence of a GOLGA8E-associated low copy repeat (LCR). Analysis of the 15q11-q13 region by PFGE also revealed a polymorphic region between BP1 and BP2. WHDC1L1 is a novel gene with similarity to mouse Whdc1 (WAS protein homology region 2 domain containing 1) and human JMY protein (junction-mediating and regulatory protein). Expression analysis of cultured human cells and brain tissues from PWS patients indicates that CYFIP1 and NIPA2 are biallelically expressed. However, we were not able to determine the allele-specific expression pattern for GOLGA8E and WHDC1L1 because these two genes have highly related sequences that might also be expressed. CONCLUSION We have presented an updated version of a sequence-based physical map for a complex chromosomal region, and we raise the possibility of polymorphism in the genomic orientation of the BP1 to BP2 region. The identification of two new proteins GOLGA8E and WHDC1L1 encoded by genes in the 15q11-q13 region may extend our understanding of the molecular basis of PWS. In terms of copy number variation and gene organization, this is one of the most polymorphic regions of the human genome, and perhaps the single most polymorphic region of this type.
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Gajecka M, Mackay KL, Shaffer LG. Monosomy 1p36 deletion syndrome. AMERICAN JOURNAL OF MEDICAL GENETICS PART C-SEMINARS IN MEDICAL GENETICS 2008; 145C:346-56. [PMID: 17918734 DOI: 10.1002/ajmg.c.30154] [Citation(s) in RCA: 135] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Monosomy 1p36 results from a heterozygous deletion of the most distal chromosomal band on the short arm of chromosome 1. Occurring in approximately 1 in 5,000 live births, monosomy 1p36 is the most common terminal deletion observed in humans. Monosomy 1p36 is associated with mental retardation, developmental delay, hearing impairment, seizures, growth impairment, hypotonia, and heart defects. The syndrome is also characterized by several distinct dysmorphic features, including large anterior fontanels, microcephaly, brachycephaly, deep-set eyes, flat nose and nasal bridge, and pointed chin. Several genes have been proposed as causative for individual features of the phenotype. In addition, based upon molecular characterization of subjects with monosomy 1p36, several mechanisms for the generation and stabilization of terminal deletions have been proposed.
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Shaffer LG, Bejjani BA, Torchia B, Kirkpatrick S, Coppinger J, Ballif BC. The identification of microdeletion syndromes and other chromosome abnormalities: cytogenetic methods of the past, new technologies for the future. AMERICAN JOURNAL OF MEDICAL GENETICS PART C-SEMINARS IN MEDICAL GENETICS 2008; 145C:335-45. [PMID: 17910076 DOI: 10.1002/ajmg.c.30152] [Citation(s) in RCA: 137] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Chromosome analysis is an important diagnostic tool in the identification of causes of mental retardation, developmental delay, and other developmental disabilities. Cytogenetic approaches have revealed the chromosomal basis of a large number of genetic syndromes. The recent use of microarray-based comparative genomic hybridization (array CGH) has accelerated the identification of novel cytogenetic abnormalities. We present the results of array CGH in 8,789 clinical cases submitted for a variety of developmental problems. Of these cases, 6.9% showed clinically relevant abnormalities, 1.2% showed benign copy-number variants (polymorphisms), 2.5% showed recurrent alterations of unclear clinical significance-many of which are likely to be polymorphisms-and 1.4% showed novel alterations of unclear relevance. Although cytogenetic methods, including array CGH, have great potential for identifying novel chromosomal syndromes, this high-resolution analysis may also result in diagnostic challenges imposed on laboratories and clinicians regarding findings of unclear clinical significance. (c) 2007 Wiley-Liss, Inc.
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Woo KS, Sung KS, Kim KU, Shaffer LG, Han JY. Characterization of complex chromosome aberrations in a recurrent meningioma combining standard cytogenetic and array comparative genomic hybridization techniques. ACTA ACUST UNITED AC 2008; 180:56-9. [DOI: 10.1016/j.cancergencyto.2007.09.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2007] [Accepted: 09/25/2007] [Indexed: 11/29/2022]
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Ballif BC, Sulpizio SG, Lloyd RM, Minier SL, Theisen A, Bejjani BA, Shaffer LG. The clinical utility of enhanced subtelomeric coverage in array CGH. Am J Med Genet A 2007; 143A:1850-7. [PMID: 17632771 DOI: 10.1002/ajmg.a.31842] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Telomeric chromosome abnormalities are a substantial cause of mental retardation and birth defects. Although subtelomeric fluorescence in situ hybridization (FISH) probes have been widely used to identify submicroscopic telomeric rearrangements, array-based comparative genomic hybridization (array CGH) has emerged as a more efficient and comprehensive detection method. Due to the clinical relevance of telomeric abnormalities, it has been proposed that array CGH using panels of BAC clones that map to regularly spaced intervals along the length of each telomere could be used to characterize subtelomeric aberrations more precisely in a single experiment. We have added 1,120 FISH-mapped BAC clones to our microarray to enhance the coverage of the 41 unique human subtelomeric regions. Contigs of clones were selected in increments of approximately 0.5 Mb beginning with the most distal unique sequence for each subtelomere and extending on average approximately 5.7 Mb toward the centromere. We have used this microarray to characterize 169 clinically significant subtelomeric abnormalities identified out of nearly 7,000 consecutive clinical cases analyzed by array CGH in our diagnostic laboratory. The expanded telomere coverage was sufficient to define the breakpoints of over half (56%) of the chromosome abnormalities. However, 44% of the subtelomeric aberrations extended beyond the size of this expanded coverage suggesting that many subtelomeric abnormalities are >5 Mb in size and that greater representation may be of even more value. In addition to identifying 6 cases of complex rearrangements, we have identified 42 cases of interstitial deletions that would have been missed by subtelomere FISH panels that use a single clone to the most distal unique sequence for each region. Microarrays designed to investigate regions known to be involved in chromosome abnormalities will enhance the detection of cytogenetic abnormalities at unprecedented resolution and frequency.
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133
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Shaffer LG, Beaudet AL, Brothman AR, Hirsch B, Levy B, Martin CL, Mascarello JT, Rao KW. Microarray analysis for constitutional cytogenetic abnormalities. Genet Med 2007; 9:654-62. [PMID: 17873655 DOI: 10.1097/gim.0b013e31814ce3d9] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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134
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Shaffer LG, Theisen A, Bejjani BA, Ballif BC, Aylsworth AS, Lim C, McDonald M, Ellison JW, Kostiner D, Saitta S, Shaikh T. The discovery of microdeletion syndromes in the post-genomic era: review of the methodology and characterization of a new 1q41q42 microdeletion syndrome. Genet Med 2007; 9:607-16. [PMID: 17873649 DOI: 10.1097/gim.0b013e3181484b49] [Citation(s) in RCA: 131] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
PURPOSE The advent of molecular cytogenetic technologies has altered the means by which new microdeletion syndromes are identified. Whereas the cytogenetic basis of microdeletion syndromes has traditionally depended on the serendipitous ascertainment of a patient with established clinical features and a chromosomal rearrangement visible by G-banding, comparative genomic hybridization using microarrays has enabled the identification of novel, recurrent imbalances in patients with mental retardation and apparently nonspecific features. Compared with the "phenotype-first" approach of traditional cytogenetics, array-based comparative genomic hybridization has enabled the detection of novel genomic disorders using a "genotype-first" approach. We report as an illustrative example the characterization of a novel microdeletion syndrome of 1q41q42. METHODS We tested more than 10,000 patients with developmental disabilities by array-based comparative genomic hybridization using our targeted microarray. High-resolution microarray analysis was performed using oligonucleotide microarrays for patients in whom deletions of 1q41q42 were identified. Fluorescence in situ hybridization was performed to confirm all 1q deletions in the patients and to exclude deletions or other chromosomal rearrangements in the parents. RESULTS Seven cases were found with de novo deletions of 1q41q42. The smallest region of overlap is 1.17 Mb and encompasses five genes, including DISP1, a gene involved in the sonic hedgehog signaling pathway, the deletion of which has been implicated in holoprosencephaly in mice. Although none of these patients showed frank holoprosencephaly, many had other midline defects (cleft palate, diaphragmatic hernia), seizures, and mental retardation or developmental delay. Dysmorphic features are present in all patients at varying degrees. Some patients showed more severe phenotypes and carry the clinical diagnosis of Fryns syndrome. CONCLUSIONS This new microdeletion syndrome with its variable clinical presentation may be responsible for a proportion of Fryns syndrome patients and adds to the increasing number of new syndromes identified with array-based comparative genomic hybridization. The genotype-first approach to identifying recurrent chromosome abnormalities is contrasted with the traditional phenotype-first approach. Targeting developmental pathways in a functional approach to diagnostics may lead to the identification of additional microdeletion syndromes.
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135
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Ballif BC, Hornor SA, Jenkins E, Madan-Khetarpal S, Surti U, Jackson KE, Asamoah A, Brock PL, Gowans GC, Conway RL, Graham JM, Medne L, Zackai EH, Shaikh TH, Geoghegan J, Selzer RR, Eis PS, Bejjani BA, Shaffer LG. Discovery of a previously unrecognized microdeletion syndrome of 16p11.2–p12.2. Nat Genet 2007; 39:1071-3. [PMID: 17704777 DOI: 10.1038/ng2107] [Citation(s) in RCA: 148] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2007] [Accepted: 06/20/2007] [Indexed: 11/08/2022]
Abstract
We have identified a recurrent de novo pericentromeric deletion in 16p11.2-p12.2 in four individuals with developmental disabilities by microarray-based comparative genomic hybridization analysis. The identification of common clinical features in these four individuals along with the characterization of complex segmental duplications flanking the deletion regions suggests that nonallelic homologous recombination mediated these rearrangements and that deletions in 16p11.2-p12.2 constitute a previously undescribed syndrome.
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136
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Campbell LJ, Slovak ML, Shaffer LG. Comments on editorial entitled “ISCN (2005) Is Not Acceptable for Describing Clonal Evolution in Cancer”. Genes Chromosomes Cancer 2007; 46:514-5; author reply 516. [PMID: 17311252 DOI: 10.1002/gcc.20430] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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137
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Ballif BC, Hornor SA, Sulpizio SG, Lloyd RM, Minier SL, Rorem EA, Theisen A, Bejjani BA, Shaffer LG. Development of a high-density pericentromeric region BAC clone set for the detection and characterization of small supernumerary marker chromosomes by array CGH. Genet Med 2007; 9:150-62. [PMID: 17413419 DOI: 10.1097/gim.0b013e3180312087] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
PURPOSE Small supernumerary marker chromosomes are centric chromosomal segments that, by definition, cannot be characterized unambiguously by conventional chromosome banding. Marker chromosomes are of particular interest in clinical cytogenetics because they are nearly 10 times more frequent in individuals with mental retardation (0.426%) than in the normal population (0.043%). However, they are often found in only a small percentage of cells, making them difficult to detect and characterize in a diagnostic setting. We designed, constructed, and employed a bacterial artificial chromosome (BAC)-based microarray to demonstrate the utility of array-based comparative genomic hybridization (array CGH) for detecting and characterizing marker chromosomes in clinical diagnostic specimens. METHODS We constructed a high-density microarray using 974 BAC clones that were mapped by fluorescence in situ hybridization and cover approximately 5 Mb of the most proximal unique sequence adjacent to the centromere on all 43 unique pericentromeric regions of the human genome (excluding the acrocentric short arms). This array was used to further characterize 20 previously identified marker chromosomes that were originally found with either conventional chromosome analysis or a targeted microarray. RESULTS The enhanced coverage of this pericentromeric array not only identified the chromosomal origin of each marker in 15 cases, it also distinguished between the involvement of the short arm and/or the long arm of each chromosome, defined the sizes of many of the markers, and revealed complex rearrangements or multiple markers in single individuals. However, in five cases, the markers could not be identified by this assay, most likely because of very low levels of mosaicism and/or their small size and lack of detectable euchromatin. The expanded coverage of the pericentromeric regions represented on the array was adequate to refine the breakpoints in two-thirds of all cases in which a marker chromosome was identified by this assay. CONCLUSIONS This study demonstrates the utility of array CGH in the detection and characterization of mosaic marker chromosomes. Because approximately one-third of the markers characterized in this study involved more unique sequence than that represented on this array, additional pericentromeric coverage may be even more valuable. We anticipate that this will allow detailed characterization of small supernumerary marker chromosomes that will greatly facilitate phenotype/genotype correlations and play a valuable role in the diagnosis and medical management of both pre- and postnatal cases in which marker chromosomes have been identified.
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138
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Jarmuz M, Glotzbach CD, Bailey KA, Bandyopadhyay R, Shaffer LG. The Evolution of satellite III DNA subfamilies among primates. Am J Hum Genet 2007; 80:495-501. [PMID: 17273970 PMCID: PMC1821104 DOI: 10.1086/512132] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2006] [Accepted: 12/16/2006] [Indexed: 01/30/2023] Open
Abstract
We demonstrate that satellite III (SatIII) DNA subfamilies cloned from human acrocentric chromosomes arose in the Hominoidea superfamily. Two groups, distinguished by sequence composition, evolved nonconcurrently, with group 2 evolving 16-23 million years ago (MYA) and the more recent group 1 sequences emerging approximately 4.5 MYA. We also show the relative order of emergence of each group 2 subfamily in the various primate species. Our results show that each SatIII subfamily is an independent evolutionary unit, that the rate of evolution is not uniform between species, and that the evolution within a species is not uniform between chromosomes.
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139
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Bejjani BA, Theisen AP, Ballif BC, Shaffer LG. Array-based comparative genomic hybridization in clinical diagnosis. Expert Rev Mol Diagn 2007; 5:421-9. [PMID: 15934818 DOI: 10.1586/14737159.5.3.421] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The sequencing of the human genome and development of high-throughput microarray technologies have enhanced the detection of copy number alterations in cancer research and the study of constitutional chromosomal abnormalities. Microarray-based comparative genomic hybridization (array CGH) has integrated molecular and traditional cytogenetics and has begun to impact the clinician's approach to medical genetics. Clinical applications of array CGH may define new genetic syndromes, expand the phenotype of existing syndromes and characterize a genomic signature of some cancers. As array CGH becomes the initial diagnostic approach for the investigation of constitutional and acquired chromosomal abnormalities, the combination of bioinformatics, robotics and microarray technology will set the stage for a new generation of high-resolution and high-throughput tools for genetic analysis, diagnosis and gene discovery.
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140
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Ballif BC, Rorem EA, Sundin K, Lincicum M, Gaskin S, Coppinger J, Kashork CD, Shaffer LG, Bejjani BA. Detection of low-level mosaicism by array CGH in routine diagnostic specimens. Am J Med Genet A 2007; 140:2757-67. [PMID: 17103431 DOI: 10.1002/ajmg.a.31539] [Citation(s) in RCA: 223] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The advent of microarray-based comparative genomic hybridization (array CGH) promises to revolutionize clinical cytogenetics because of its ability to rapidly screen the genome at an unprecedented resolution. Yet, the ability of array CGH to detect and evaluate low-level mosaicism is not known. Our laboratory has analyzed over 3,600 clinical cases with the SignatureChip which we developed for the detection of microdeletions, microduplications, aneuploidy, unbalanced translocations, and subtelomeric and pericentromeric copy number alterations. Here, we report 18 cases of mosaicism detected by array CGH in a routine diagnostic setting, 14 of which were not known to us at the time of the analysis. These 14 cases represent approximately 8% of all abnormal cases identified in our laboratory. For each case, fluorescence in situ hybridization (FISH) analysis was performed on PHA-stimulated cultures after mosaic chromosome abnormalities were suspected by array CGH. In all cases, FISH confirmed the mosaic chromosome abnormalities which included a variety of marker chromosomes, autosomal trisomies, terminal and interstitial deletions, and derivative chromosomes. Interestingly, confirmatory FISH analyses on direct blood smears indicated that the percentage of abnormal cells in unstimulated cultures was in some cases different than that found in PHA-stimulated cells. We also report the detection of a previously unsuspected case of an isochromosome 12p (associated with Pallister-Killian syndrome) by array CGH using genomic DNA extracted from peripheral blood. These results support a growing body of data that suggests that stimulated peripheral blood cultures likely distort the percentage of abnormal cells and may, for some chromosome abnormalities, make their detection unlikely by conventional analysis. Thus, array CGH, which is based on genomic DNA extracted directly from uncultured peripheral blood, may be more likely to detect low-level mosaicism for unbalanced chromosome abnormalities than traditional cytogenetic techniques.
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141
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Bejjani BA, Shaffer LG. Application of array-based comparative genomic hybridization to clinical diagnostics. J Mol Diagn 2007; 8:528-33. [PMID: 17065418 PMCID: PMC1876176 DOI: 10.2353/jmoldx.2006.060029] [Citation(s) in RCA: 124] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Microarray-based comparative genomic hybridization (array CGH) is a revolutionary platform that was recently adopted in the clinical laboratory. This technology was first developed as a research tool for the investigation of genomic alterations in cancer. It allows for a high-resolution evaluation of DNA copy number alterations associated with chromosome abnormalities. Array CGH is based on the use of differentially labeled test and reference genomic DNA samples that are simultaneously hybridized to DNA targets arrayed on a glass slide or other solid platform. In this review, we examine the technology and its transformation from a research tool into a maturing diagnostic instrument. We also evaluate the various approaches that have shaped the current platforms that are used for clinical applications. Finally, we discuss the advantages and shortcomings of "whole-genome" arrays and compare their diagnostic use to "targeted" arrays. Depending on their design, microarrays provide distinct advantages over conventional cytogenetic analysis because they have the potential to detect the majority of microscopic and submicroscopic chromosomal abnormalities. This new platform is poised to revolutionize modern cytogenetic diagnostics and to provide clinicians with a powerful tool to use in their increasingly sophisticated diagnostic capabilities.
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142
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Shaffer LG, Bui TH. Molecular cytogenetic and rapid aneuploidy detection methods in prenatal diagnosis. AMERICAN JOURNAL OF MEDICAL GENETICS PART C-SEMINARS IN MEDICAL GENETICS 2007; 145C:87-98. [PMID: 17290441 DOI: 10.1002/ajmg.c.30114] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Cytogenetic analysis is an important component of prenatal diagnosis. The ability to rapidly detect aneuploidy and identify small structural abnormalities of fetal chromosomes has been greatly enhanced by the use of molecular cytogenetic technologies. In this review, we will present some of the molecular cytogenetic techniques available to the clinical cytogenetics laboratory. These include fluorescence in situ hybridization (FISH), quantitative fluorescence PCR (QF-PCR), multiplex ligation-dependent probe amplification (MLPA) and microarray-based comparative genomic hybridization (array CGH). The benefits and limitations of each technology will be discussed in the context of prenatal diagnosis.
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143
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Shaffer LG, Bejjani BA. Medical applications of array CGH and the transformation of clinical cytogenetics. Cytogenet Genome Res 2006; 115:303-9. [PMID: 17124414 DOI: 10.1159/000095928] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2006] [Accepted: 05/02/2006] [Indexed: 11/19/2022] Open
Abstract
Microarray-based comparative genomic hybridization (array CGH) merges molecular diagnostics with traditional chromosome analysis and is transforming the field of cytogenetics. Prospective studies of individuals with developmental delay and dysmorphic features have demonstrated that array CGH has the ability to detect any genomic imbalance including deletions, duplications, aneuploidies and amplifications. Detection rates for chromosome abnormalities with array CGH range from 5-17% in individuals with normal results from prior routine cytogenetic testing. In addition, copy number variants (CNVs) were identified in all studies. These CNVs may include large-scale variation and can confound the diagnostic interpretations. Although cytogeneticists will require additional training and laboratories must become appropriately equipped, array CGH holds the promise of being the initial diagnostic tool in the identification of visible and submicroscopic chromosome abnormalities in mental retardation and other developmental disabilities.
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144
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145
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Jarmuz M, Shaffer LG. Cytogenetic analysis of cardiovascular disease: karyotyping. METHODS IN MOLECULAR MEDICINE 2006; 128:1-9. [PMID: 17071985 DOI: 10.1007/978-1-59745-159-8_1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Numerical and structural chromosomal rearrangements, such as aneuploidies, deletions, duplications, and other aberrations have been associated with congenital abnormalities, pregnancy loss, and malignancy. Detection of these genetic changes is possible by cytogenetic analysis. The karyotype is determined by analysis of metaphase or prometaphase chromosomes of peripheral blood lymphocytes after banding procedures. This analysis plays an important role in determining patient diagnosis and care. In this chapter, we describe the basic approach of cytogenetic analysis: arresting the cell in metaphase or prometaphase, the obtaining of metaphase chromosome spreads, and staining and chromosome analysis.
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146
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Biggerstaff JS, Liu W, Slovak ML, Bobadilla D, Bryant E, Glotzbach C, Shaffer LG. A dual-color FISH assay distinguishes between ELL and MLLT1 (ENL) gene rearrangements in t(11;19)-positive acute leukemia. Leukemia 2006; 20:2046-50. [PMID: 16990786 DOI: 10.1038/sj.leu.2404371] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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147
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Baris H, Bejjani BA, Tan WH, Coulter DL, Martin JA, Storm AL, Burton BK, Saitta SC, Gajecka M, Ballif BC, Irons MB, Shaffer LG, Kimonis VE. Identification of a novel polymorphism—the duplication of theNPHP1 (nephronophthisis 1) gene. Am J Med Genet A 2006; 140A:1876-9. [PMID: 16892302 DOI: 10.1002/ajmg.a.31390] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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148
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Kashork CD, Theisen A, Bejjani BA, Shaffer LG. Rearrangements of chromosome 18 illustrate the utility of array-based comparative genomic hybridization. Cytogenet Genome Res 2006; 114:379-83. [PMID: 16954681 DOI: 10.1159/000094228] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2005] [Accepted: 04/02/2006] [Indexed: 11/19/2022] Open
Abstract
Comprehensive and reliable testing is an important component of counseling and management in clinical genetics. Identification of imbalances of chromosomal segments has uncovered new genes and has established phenotype/genotype correlations for many syndromes with previously unidentified causes. Conventional cytogenetics has proven to be useful for the detection of large aberrations, but its resolution limits the identification of submicroscopic alterations. Comparative genomic hybridization (CGH) on a microarray-based platform has the potential to detect and characterize both microscopic and submicroscopic chromosomal abnormalities. Nine cases of aberrations involving chromosome 18 are used to illustrate the use and clinical potential of array CGH.
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Gajecka M, Glotzbach CD, Jarmuz M, Ballif BC, Shaffer LG. Identification of cryptic imbalance in phenotypically normal and abnormal translocation carriers. Eur J Hum Genet 2006; 14:1255-62. [PMID: 16941016 DOI: 10.1038/sj.ejhg.5201710] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Approximately one in 500 individuals carries a reciprocal translocation. Of the 121 monosomy 1p36 subjects ascertained by our laboratory, three independent cases involved unbalanced translocations of 1p and 9q, all of which were designated t(1;9)(p36.3;q34). These derivative chromosomes were inherited from balanced translocation carrier parents. To understand better the causes and consequences of chromosome breakage and rearrangement in the human genome, we characterized each derivative chromosome at the DNA sequence level and identified the junctions between 1p36 and 9q34. The breakpoint regions were unique in all individuals. Insertions and duplications were identified in two balanced translocation carrier parents and their unbalanced offspring. Sequence analyses revealed that the translocation breakpoints disrupted genes. This study demonstrates that apparently balanced reciprocal translocations in phenotypically normal carriers may have cryptic imbalance at the breakpoints. Because disrupted genes were identified in the phenotypically normal translocation carriers, caution should be exercised when interpreting data on phenotypically abnormal carriers with apparently balanced rearrangements that disrupt putative candidate genes.
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Gajecka M, Pavlicek A, Glotzbach CD, Ballif BC, Jarmuz M, Jurka J, Shaffer LG. Identification of sequence motifs at the breakpoint junctions in three t(1;9)(p36.3;q34) and delineation of mechanisms involved in generating balanced translocations. Hum Genet 2006; 120:519-26. [PMID: 16847692 DOI: 10.1007/s00439-006-0222-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2006] [Accepted: 06/16/2006] [Indexed: 01/24/2023]
Abstract
Although approximately 1 in 500 individuals carries a reciprocal translocation, little is known about the mechanisms that result in their formation. We analyzed the sequences surrounding the breakpoints in three unbalanced translocations of 1p and 9q, all of which were designated t(1;9)(p36.3;q34), to investigate the presence of sequence motifs that might mediate nonhomologous end joining (NHEJ). The breakpoint regions were unique in all individuals. Two of three translocations demonstrated insertions and duplications at the junctions, suggesting NHEJ in the formation of the rearrangements. No homology was identified in the breakpoint regions, further supporting NHEJ. We found translin motifs at the breakpoint junctions, suggesting the involvement of translin in the joining of the broken chromosome ends. We propose a model for balanced translocation formation in humans similar to transposition in bacteria, in which staggered nicks are repaired resulting in duplications and insertions at the translocation breakpoints.
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