151
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Fridman C, Varela MC, Kok F, Diament A, Koiffmann CP. Paternal UPD15: further genetic and clinical studies in four Angelman syndrome patients. AMERICAN JOURNAL OF MEDICAL GENETICS 2000; 92:322-7. [PMID: 10861661 DOI: 10.1002/1096-8628(20000619)92:5<322::aid-ajmg6>3.0.co;2-y] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Among 25 patients diagnosed with Angelman syndrome, we detected 21 with deletion and 4 with paternal uniparental disomy (UPD), 2 isodisomies originating by postzygotic error, and 1 MII nondisjunction event. The diagnosis was obtained by molecular techniques, including methylation pattern analysis of exon 1 of SNRPN and microsatellite analysis of loci within and outside the 15q11-q13 region. Most manifestations present in deletion patients are those previously reported. Comparing the clinical data from our and published UPD patients with those with deletions we observed the following: the age of diagnosis is higher in UPD group (average 7 3/12 years), microcephaly is more frequent among deletion patients, UPD children start walking earlier (average age 2 9/12 years), whereas in deletion patients the average is 4 (1/2) years, epilepsy started later in UPD patients (average 5 10/12 years) than in deletion patients (average 1 11/12 years), weight above the 75th centile is reported mainly in UPD patients, complete absence of speech is more common in the deleted (88.9%) than in the UPD patients because half of the children are able to say few words. Thus, besides the abnormalities already described, the UPD patients have somewhat better verbal development, a weight above the 75th centile, and OFC in the upper normal range.
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Affiliation(s)
- C Fridman
- Department of Biology, Institute of Bioscience, University of São Paulo, Brazil.
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152
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Nogami M, Kohda A, Taguchi H, Nakao M, Ikemura T, Okumura K. Relative locations of the centromere and imprinted SNRPN gene within chromosome 15 territories during the cell cycle in HL60 cells. J Cell Sci 2000; 113 ( Pt 12):2157-65. [PMID: 10825289 DOI: 10.1242/jcs.113.12.2157] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Investigations of imprinted regions provide clues that increase our understanding of the regulation of gene functions at higher order chromosomal domains. Here, the relative positions of the chromosome 15 centromere and the imprinted SNRPN gene in interphase nuclei of human myeloid leukemia HL60 cells were compared, because the homologous association of this imprinted chromosomal domain was previously observed in lymphocytes and lymphoblasts. Four targets including the chromosome 15 territory, its centromere, the SNRPN gene on this chromosome, and the nucleus, were visualized simultaneously in three-dimensionally preserved nuclei using multicolor fluorescence in situ hybridization, and the spatial distributions of these probes were analyzed with a cooled CCD camera deconvolution system. We found that preferential association of SNRPN interhomologues did not occur during the cell cycle in HL60 cells, although this gene exhibited asynchronous replication and monoallelic expression in this cells. SNRPN was found to localize at the periphery of the chromosome territories, and it preferentially faced the nuclear membrane, unlike the adjacent centromeric repeat. The SNRPN gene and the centromere were located close to each other late in S phase, reflecting that these DNA segments may be compacted into the same intranuclear subcompartments with the progress of S phase and in course of preparation for the following G(2) phase. Our results suggest that, although an imprinted gene has features similar to those observed with intranuclear localization of other gene coding sequences, the characteristic of mutual recognition of imprinted regions is determined by certain cellular regulation, and it is not necessary for the allele-specific features of an imprinted gene.
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Affiliation(s)
- M Nogami
- Laboratory of Molecular and Cellular Biology, Faculty of Bioresources, Mie University, Tsu, Mie 514-8507, Japan
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153
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Doherty AS, Mann MR, Tremblay KD, Bartolomei MS, Schultz RM. Differential effects of culture on imprinted H19 expression in the preimplantation mouse embryo. Biol Reprod 2000; 62:1526-35. [PMID: 10819752 DOI: 10.1095/biolreprod62.6.1526] [Citation(s) in RCA: 511] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
The H19 gene is imprinted with preferential expression from the maternal allele. The putative imprinting control region for this locus is hypermethylated on the repressed paternal allele. Although maternal-specific expression of H19 is observed in mouse blastocysts that develop in vivo, biallelic expression has been documented in embryos and embryonic stem cells experimentally manipulated by in vitro culture conditions. In this study the effect of culture on imprinted H19 expression and methylation was determined. After culture of 2-cell embryos to the blastocyst stage in Whitten's medium, the normally silent paternal H19 allele was aberrantly expressed, whereas little paternal expression was observed following culture in KSOM containing amino acids (KSOM+AA). Analysis of the methylation status of a CpG dinucleotide located in the upstream imprinting control region revealed a loss in methylation in embryos cultured in Whitten's medium but not in embryos cultured in KSOM+AA. Thus, H19 expression and methylation were adversely affected by culture in Whitten's medium, while the response of H19 to culture in KSOM+AA approximated more closely the in vivo situation. It is unlikely that biallelic expression of H19 following culture in Whitten's medium is a generalized effect of lower methylation levels, since the amount of DNA methyltransferase activity and the spatial distribution of Dnmt1 protein were similar in in vivo-derived and cultured embryos. Moreover, imprinted expression of Snrpn was maintained following culture in either medium, indicating that not all imprinted genes are under the same stringent imprinting controls. The finding that culture conditions can dramatically, but selectively, affect the expression of imprinted genes provides a model system for further study of the linkage between DNA methylation and gene expression.
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Affiliation(s)
- A S Doherty
- Department of Biology and Howard Hughes Medical Institute, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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154
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Schwienbacher C, Gramantieri L, Scelfo R, Veronese A, Calin GA, Bolondi L, Croce CM, Barbanti-Brodano G, Negrini M. Gain of imprinting at chromosome 11p15: A pathogenetic mechanism identified in human hepatocarcinomas. Proc Natl Acad Sci U S A 2000; 97:5445-9. [PMID: 10779553 PMCID: PMC25848 DOI: 10.1073/pnas.090087497] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Genomic imprinting is a reversible condition that causes parental-specific silencing of maternally or paternally inherited genes. Analysis of DNA and RNA from 52 human hepatocarcinoma samples revealed abnormal imprinting of genes located at chromosome 11p15 in 51% of 37 informative samples. The most frequently detected abnormality was gain of imprinting, which led to loss of expression of genes present on the maternal chromosome. As compared with matched normal liver tissue, hepatocellular carcinomas showed extinction or significant reduction of expression of one of the alleles of the CDKN1C, SLC22A1L, and IGF2 genes. Loss of maternal-specific methylation at the KvDMR1 locus in hepatocarcinoma correlated with abnormal expression of CDKN1C and IGF2, suggesting a function for KvDMR1 as a long-range imprinting center active in adult tissues. These results point to the role of epigenetic mechanisms leading to loss of expression of imprinted genes at chromosome region 11p15 in human tumors.
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Affiliation(s)
- C Schwienbacher
- Dipartimento di Medicina Sperimentale e Diagnostica, Università di Ferrara, via Luigi Borsari 46, 44100 Ferrara, Italy
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155
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Bielinska B, Blaydes SM, Buiting K, Yang T, Krajewska-Walasek M, Horsthemke B, Brannan CI. De novo deletions of SNRPN exon 1 in early human and mouse embryos result in a paternal to maternal imprint switch. Nat Genet 2000; 25:74-8. [PMID: 10802660 DOI: 10.1038/75629] [Citation(s) in RCA: 114] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Prader-Willi syndrome (PWS) is a neurogenetic disease characterized by infantile hypotonia, gonadal hypoplasia, obsessive behaviour and neonatal feeding difficulties followed by hyperphagia, leading to profound obesity. PWS is due to a lack of paternal genetic information at 15q11-q13 (ref. 2). Five imprinted, paternally expressed genes map to the PWS region, MKRN3 (ref. 3), NDN (ref. 4), NDNL1 (ref. 5), SNRPN (refs 6-8 ) and IPW (ref. 9), as well as two poorly characterized framents designated PAR-1 and PAR-5 (ref. 10). Imprinting of this region involves a bipartite 'imprinting centre' (IC), which overlaps SNRPN (refs 10,11). Deletion of the SNRPN promoter/exon 1 region (the PWS IC element) appears to impair the establishment of the paternal imprint in the male germ line and leads to PWS. Here we report a PWS family in which the father is mosaic for an IC deletion on his paternal chromosome. The deletion chromosome has acquired a maternal methylation imprint in his somatic cells. We have made identical findings in chimaeric mice generated from two independent embryonic stem (ES) cell lines harbouring a similar deletion. Our studies demonstrate that the PWS IC element is not only required for the establishment of the paternal imprint, but also for its postzygotic maintenance.
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Affiliation(s)
- B Bielinska
- Department of Genetics, The Children's Memorial Health Institute, Warsaw, Poland
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156
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Ming JE, Blagowidow N, Knoll JH, Rollings L, Fortina P, McDonald-McGinn DM, Spinner NB, Zackai EH. Submicroscopic deletion in cousins with Prader-Willi syndrome causes a grandmatrilineal inheritance pattern: effects of imprinting. AMERICAN JOURNAL OF MEDICAL GENETICS 2000; 92:19-24. [PMID: 10797418 DOI: 10.1002/(sici)1096-8628(20000501)92:1<19::aid-ajmg4>3.0.co;2-#] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The Prader-Willi syndrome (PWS) critical region on 15q11-q13 is subject to imprinting. PWS becomes apparent when genes on the paternally inherited chromosome are not expressed. Familial PWS is rare. We report on a family in which a male and a female paternal first cousin both have PWS with cytogenetically normal karyotypes. Fluorescence in situ hybridization (FISH) analysis shows a submicroscopic deletion of SNRPN, but not the closely associated loci D15S10, D15S11, D15S63, and GABRB3. The cousins' fathers and two paternal aunts have the same deletion and are clinically normal. The grandmother of the cousins is deceased and not available for study, and their grandfather is not deleted for SNRPN. DNA methylation analysis of D15S63 is consistent with an abnormality of the imprinting center associated with PWS. "Grandmatrilineal" inheritance occurs when a woman with deletion of an imprinted, paternally expressed gene is at risk of having affected grandchildren through her sons. In this case, PWS does not become evident as long as the deletion is passed through the matrilineal line. This represents a unique inheritance pattern due to imprinting.
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Affiliation(s)
- J E Ming
- Division Human Genetics and Molecular Biology Hematology, Department of Pediatrics, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA.
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157
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Färber C, Gross S, Neesen J, Buiting K, Horsthemke B. Identification of a testis-specific gene (C15orf2) in the Prader-Willi syndrome region on chromosome 15. Genomics 2000; 65:174-83. [PMID: 10783265 DOI: 10.1006/geno.2000.6158] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Prader-Willi syndrome (PWS) results from the loss of paternal contributions for a 2-Mb imprinted region on the proximal long arm of human chromosome 15. Hitherto, five paternally active genes have been identified in this region (ZNF127, NDN, MAGEL2, SNURF-SNRPN, and IPW). Here we report the identification of a novel gene in the PWS critical region, which has been designated "chromosome 15 open reading frame 2" (C15orf2). C15orf2 is an intronless gene located between MAGEL2 and SNURF-SNRPN. It is associated with a CpG island, which is methylated in all tissues tested except for germ cells. C15orf2 is transcribed as a 7.5-kb mRNA and contains an open reading frame encoding a predicted 1156-amino-acid protein of unknown function. Transcription of C15orf2 occurs exclusively in the testis, and in adult testis samples, we observed biallelic expression. By zoo-blot analysis, we found related sequences in DNA from other primates, but not in nonprimate DNA. We conclude that C15orf2 may play a role in primate spermatogenesis.
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Affiliation(s)
- C Färber
- Institut für Humangenetik, Universitätsklinikum Essen, Hufelandstrasse 55, Essen, D-45122, Germany
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158
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Buettner VL, LeBon JM, Gao C, Riggs AD, Singer-Sam J. Use of terminal transferase-dependent antisense RNA amplification to determine the transcription start site of the Snrpn gene in individual neurons. Nucleic Acids Res 2000; 28:E25. [PMID: 10710442 PMCID: PMC102808 DOI: 10.1093/nar/28.7.e25] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/1999] [Revised: 01/04/2000] [Accepted: 01/20/2000] [Indexed: 11/14/2022] Open
Abstract
We describe here a very sensitive technique for RNA structure analysis and the determination of transcription start sites and demonstrate its use for mapping the start site of the imprinted Snrpn gene in individual hippocampal neurons. The method is adapted from reverse transcription-terminal transferase-dependent PCR (RT-TDPCR) to include amplification of the antisense sequence by in vitro transcription just prior to the final PCR step. The method should be useful for analysis of all genes for which variation in promoter usage and/or differences in RNA secondary structure may be specific to a given cell type or developmental stage.
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Affiliation(s)
- V L Buettner
- Mammalian Genetics and Molecular Biology Sections, Biology Department, Beckman Research Institute of the City of Hope, Duarte, CA 91010, USA
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159
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Annerén G, Tuvemo T, Gustafsson J. Growth hormone therapy in young children with Down syndrome and a clinical comparison of Down and Prader-Willi syndromes. Growth Horm IGF Res 2000; 10 Suppl B:S87-S91. [PMID: 10984260 DOI: 10.1016/s1096-6374(00)80016-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The genetic disorders Prader-Willi syndrome and Down syndrome have a number of features in common, for example, both growth and mental retardation. Growth hormone (GH) treatment is becoming part of the clinical management of children with Prader-Willi syndrome, but in children with Down syndrome, such therapy is still on a research level. In this review, we compare the clinical phenotypes of the two syndromes, and report the effects of long-term GH treatment on the linear growth and psychomotor development of 15 young children with Down syndrome (mean age at start of treatment, 7.4 months). The mean height of the treated children with Down syndrome increased significantly from -1.8 to -0.8 SDS (Swedish standard) during the 3 years of GH therapy (P < 0.001). The mean height of a corresponding control group fell from -1.7 to -2.2 SDS. After the cessation of treatment, growth velocity declined in the treated group. Growth of the head did not increase during GH treatment. There was no effect on mental or gross-motor development, although some improvement in fine-motor development was noted in the GH-treated group (P < 0.01). At present, treatment with GH is not recommended in children with Down syndrome who have not been diagnosed with GH deficiency. Long-term studies with an emphasis also on the metabolic effects of GH therapy are necessary before routine treatment can be considered in such children.
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Affiliation(s)
- G Annerén
- Department of Genetics and Pathology, Uppsala University, Sweden.
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160
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Glenn CC, Deng G, Michaelis RC, Tarleton J, Phelan MC, Surh L, Yang TP, Driscoll DJ. DNA methylation analysis with respect to prenatal diagnosis of the Angelman and Prader-Willi syndromes and imprinting. Prenat Diagn 2000. [DOI: 10.1002/(sici)1097-0223(200004)20:4<300::aid-pd803>3.0.co;2-a] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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161
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Lee S, Wevrick R. Identification of novel imprinted transcripts in the Prader-Willi syndrome and Angelman syndrome deletion region: further evidence for regional imprinting control. Am J Hum Genet 2000; 66:848-58. [PMID: 10712201 PMCID: PMC1288168 DOI: 10.1086/302817] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Deletions and other abnormalities of human chromosome 15q11-q13 are associated with two developmental disorders, Prader-Willi syndrome (PWS) and Angelman syndrome (AS). Loss of expression of imprinted, paternally expressed genes has been implicated in PWS. However, the number of imprinted genes that contribute to PWS, and the range over which the imprinting signal acts to silence one copy of the gene in a parent-of-origin-specific manner, are unknown. To identify additional imprinted genes that could contribute to the PWS phenotype and to understand the regional control of imprinting in 15q11-q13, we have constructed an imprinted transcript map of the PWS-AS deletion interval. The imprinting status of 22 expressed sequence tags derived from the radiation-hybrid human transcript maps or physical maps was determined in a reverse transcriptase-PCR assay and correlated with the position of the transcripts on the physical map. Seven new paternally expressed transcripts localize to an approximately 1.5-Mb domain surrounding the SNRPN-associated imprinting center, which already includes four imprinted, paternally expressed genes. All other tested new transcripts in the deletion region were expressed from both alleles. A domain of exclusive paternal expression surrounding the imprinting center suggests strong regional control of the imprinting process. This study provides the means for further investigation of additional genes that cause or modify the phenotypes associated with rearrangements of 15q11-q13.
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Affiliation(s)
- S Lee
- Department of Medical Genetics, University of Alberta, Edmonton, Alberta, Canada T6G 2H7
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162
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Sunahara S, Nakamura K, Nakao K, Gondo Y, Nagata Y, Katsuki M. The oocyte-specific methylated region of the U2afbp-rs/U2af1-rs1 gene is dispensable for its imprinted methylation. Biochem Biophys Res Commun 2000; 268:590-5. [PMID: 10679248 DOI: 10.1006/bbrc.2000.2189] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Imprinted genes harbor discrete regions which are differentially methylated in gametes; usually the final differential methylation patterns in adults are established during embryogenesis through modifications of the initial methylation patterns in gametes. Previous reports have shown that a 200-bp region termed region II within the CpG island of the mouse imprinted U2afbp-rs gene is methylated in oocytes but not in sperm, suggesting that this region is a center for the propagation of methylated CpGs on the maternal allele and is also a candidate for an imprinting control element. To determine whether region II is required for the imprinted methylation of this gene at the endogenous locus, we generated mice carrying a deletion of this region. We herein show that parental methylation differences still exist in the CpG island on the region II-deleted allele. These findings suggest that region II is dispensable for the imprinted methylation of the U2afbp-rs gene.
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Affiliation(s)
- S Sunahara
- Division of DNA Biology and Embryo Engineering, CREST, Center for Experimental Medicine, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Tokyo, Minato-ku, 108-8639, Japan
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163
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Velinov M, Gu H, Genovese M, Duncan C, Brown WT, Jenkins E. The feasibility of PCR-based diagnosis of Prader-Willi and Angelman syndromes using restriction analysis after bisulfite modification of genomic DNA. Mol Genet Metab 2000; 69:81-3. [PMID: 10655162 DOI: 10.1006/mgme.1999.2941] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have developed a novel PCR-based method for studying DNA methylation in the proximal region of 15q, using restriction analysis after bisulfite treatment of genomic DNA. This protocol can be used for the diagnosis of Prader-Willi and Angelman syndromes. Unlike the recently reported methylation-specific PCR protocol, our method avoids the use of multiplex amplification, thus overcoming the need to adjust relative primer amounts and the risk of obtaining false-negative results.
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Affiliation(s)
- M Velinov
- NYS Institute for Basic Research in Developmental Disabilities, 1050 Forest Hill Road, Staten Island, New York, 10314, USA
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164
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Buiting K, Dittrich B, Dworniczak B, Lerer I, Abeliovich D, Cottrell S, Temple IK, Harvey JF, Lich C, Gross S, Horsthemke B. A 28-kb deletion spanning D15S63 (PW71) in five families: a rare neutral variant? Am J Hum Genet 1999; 65:1588-94. [PMID: 10577912 PMCID: PMC1288369 DOI: 10.1086/302670] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Methylation analysis with probe PW71 (D15S63) is an established procedure to test patients suspected of having Prader-Willi syndrome or Angelman syndrome. Using this test, we have identified a 28-kb deletion spanning D15S63 in five independent families. Sequence analysis revealed identical breakpoints in all the families. The haplotype data are compatible with a common ancestral origin of the deletion in at least two families. The deletion was not found in 1, 000 unrelated controls. Although the deletion maps within the imprinting-center region, neither maternal nor paternal inheritance of the deletion appears to affect imprinting in proximal 15q. We conclude that the deletion is a rare neutral variant that can lead to false-positive results in the PW71-methylation test.
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Affiliation(s)
- K Buiting
- Institut für Humangenetik, Universitätsklinkum Essen, 45122 Essen, Germany
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165
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Boccaccio I, Glatt-Deeley H, Watrin F, Roëckel N, Lalande M, Muscatelli F. The human MAGEL2 gene and its mouse homologue are paternally expressed and mapped to the Prader-Willi region. Hum Mol Genet 1999; 8:2497-505. [PMID: 10556298 DOI: 10.1093/hmg/8.13.2497] [Citation(s) in RCA: 128] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Prader-Willi syndrome (PWS) is a complex neurogenetic disorder. The phenotype is likely to be a contiguous gene syndrome involving genes which are paternally expressed only, located in the human 15q11-q13 region. Four mouse models of PWS have been reported but these do not definitively allow the delineation of the critical region and the associated genes involved in the aetiology of PWS. Moreover, targeted mutagenesis of mouse homologues of the human candidate PWS genes does not appear to result in any of the features of PWS. Therefore, the isolation of new genes in this region remains crucial for a better understanding of the molecular basis of PWS. In this manuscript, we report the characterization of MAGEL2 and its mouse homologue Magel2. These are located in the human 15q11-q13 and mouse 7C regions, in close proximity to NDN / Ndn. By northern blot analysis we did not detect any expression of MAGEL2 / Magel2 but by RT-PCR analysis, specific expression was detected in fetal and adult brain and in placenta. Both genes are intronless with tandem direct repeat sequences contained within a CpG island in the 5'-untranscribed region. The transcripts encode putative proteins that are homologous to the MAGE proteins and NDN. Moreover, MAGEL2 / Magel2 are expressed only from the paternal allele in brain, suggesting a potential role in the aetiology of PWS and its mouse model, respectively.
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Affiliation(s)
- I Boccaccio
- INSERM U491, Faculté de Médecine, 27 Boulevard Jean Moulin, F-13385 Marseille Cedex 5, France
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166
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Miura K, Obama M, Yun K, Masuzaki H, Ikeda Y, Yoshimura S, Akashi T, Niikawa N, Ishimaru T, Jinno Y. Methylation imprinting of H19 and SNRPN genes in human benign ovarian teratomas. Am J Hum Genet 1999; 65:1359-67. [PMID: 10521301 PMCID: PMC1288288 DOI: 10.1086/302615] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
In humans, studies of female germ cells are very limited by ethics. The current study investigated the usefulness of benign ovarian teratomas as a substitute for ova in analyses of imprinted genes. Twenty-five human benign ovarian teratomas were typed with 45 microsatellite DNA markers and classified according to their genotypic features. Two oppositely imprinted genes, H19 and SNRPN, were then chosen for analysis of their methylation states in these tumors. These analyses revealed that benign ovarian teratomas consist of a mixture of genetically and epigenetically heterogeneous cell populations. In contrast to previous reports, we could document only one case rising from germ cells by meiosis-II nondisjunction. H19 and SNRPN were methylated in individual teratomas to various degrees, ranging from normal somatic cell to expected ovum levels. The allele with residual methylation of H19 was consistent with that methylated in the patient's blood DNA, thus being of paternal origin. Degrees of H19 hypomethylation and SNRPN hypermethylation increased as the cellular origin of the tumors advanced in oogenesis and were closely correlated in individual teratomas. These results could be best explained by the assumption that the primary imprinting is a progressively organized process and suggest that the establishment of primary imprints on different genes might be mechanistically linked, even when those genes are oppositely imprinted.
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Affiliation(s)
- K. Miura
- Departments of Human Genetics and Obstetrics and Gynecology, Nagasaki University School of Medicine, Nagasaki; and Department of Pathology, University of Otago Medical School, Dunedin, New Zealand
| | - M. Obama
- Departments of Human Genetics and Obstetrics and Gynecology, Nagasaki University School of Medicine, Nagasaki; and Department of Pathology, University of Otago Medical School, Dunedin, New Zealand
| | - K. Yun
- Departments of Human Genetics and Obstetrics and Gynecology, Nagasaki University School of Medicine, Nagasaki; and Department of Pathology, University of Otago Medical School, Dunedin, New Zealand
| | - H. Masuzaki
- Departments of Human Genetics and Obstetrics and Gynecology, Nagasaki University School of Medicine, Nagasaki; and Department of Pathology, University of Otago Medical School, Dunedin, New Zealand
| | - Y. Ikeda
- Departments of Human Genetics and Obstetrics and Gynecology, Nagasaki University School of Medicine, Nagasaki; and Department of Pathology, University of Otago Medical School, Dunedin, New Zealand
| | - S. Yoshimura
- Departments of Human Genetics and Obstetrics and Gynecology, Nagasaki University School of Medicine, Nagasaki; and Department of Pathology, University of Otago Medical School, Dunedin, New Zealand
| | - T. Akashi
- Departments of Human Genetics and Obstetrics and Gynecology, Nagasaki University School of Medicine, Nagasaki; and Department of Pathology, University of Otago Medical School, Dunedin, New Zealand
| | - N. Niikawa
- Departments of Human Genetics and Obstetrics and Gynecology, Nagasaki University School of Medicine, Nagasaki; and Department of Pathology, University of Otago Medical School, Dunedin, New Zealand
| | - T. Ishimaru
- Departments of Human Genetics and Obstetrics and Gynecology, Nagasaki University School of Medicine, Nagasaki; and Department of Pathology, University of Otago Medical School, Dunedin, New Zealand
| | - Y. Jinno
- Departments of Human Genetics and Obstetrics and Gynecology, Nagasaki University School of Medicine, Nagasaki; and Department of Pathology, University of Otago Medical School, Dunedin, New Zealand
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167
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Simon I, Tenzen T, Reubinoff BE, Hillman D, McCarrey JR, Cedar H. Asynchronous replication of imprinted genes is established in the gametes and maintained during development. Nature 1999; 401:929-32. [PMID: 10553911 DOI: 10.1038/44866] [Citation(s) in RCA: 132] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Genomic imprinting is characterized by allele-specific expression of multiple genes within large chromosomal domains that undergo DNA replication asynchronously during S phase. Here we show, using both fluorescence in situ hybridization analysis and S-phase fractionation techniques, that differential replication timing is associated with imprinted genes in a variety of cell types, and is already present in the pre-implantation embryo soon after fertilization. This pattern is erased before meiosis in the germ line, and parent-specific replication timing is then reset in late gametogenesis in both the male and female. Thus, asynchronous replication timing is established in the gametes and maintained throughout development, indicating that it may function as a primary epigenetic marker for distinguishing between the parental alleles.
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Affiliation(s)
- I Simon
- Department of Cellular Biochemistry, Hebrew University, Jerusalem, Israel
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168
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Kuzmin I, Geil L, Ge H, Bengtsson U, Duh FM, Stanbridge EJ, Lerman MI. Analysis of aberrant methylation of the VHL gene by transgenes, monochromosome transfer, and cell fusion. Oncogene 1999; 18:5672-9. [PMID: 10523847 DOI: 10.1038/sj.onc.1202959] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Several tumor suppressor genes were shown to be inactivated by a process involving aberrant de novo methylation of their GC-rich promoters which is usually associated with transcriptional repression. The mechanisms underlying this process are poorly understood. In particular this abnormal methylation may be caused and/or maintained by either deficiency of some trans-acting factor(s) or by various malfunctions acting in cis. Here we studied the nature of aberrant methylation of the von Hippel-Lindau (VHL) disease tumor suppressor gene in a human clear cell renal carcinoma cell line, UOK 121, that contains a silent hypermethylated endogenous VHL allele. First, we transfected unmethylated VHL transgenes, driven by the VHL promoter, into UOK 121 cells. Next, to exclude possible position effects that may influence methylation of the introduced VHL genes, we transferred a single chromosome 3, carrying an apparently normal hypomethylated VHL allele into the UOK 121 cells. Finally, we created somatic cell hybrids between UOK 121 and UMRC 6 cells containing a mutant VHL-expressing hypomethylated allele. In these three experiments both the methylation of the VHL promoter and the transcriptional status of the introduced and endogenous VHL alleles remained unchanged. Our results demonstrate that the putative trans-acting factors present in the UOK 121 and UMRC 6 cells are unable to induce changes in methylation pattern of the VHL alleles in all cell lines and hybrids studied. Taken together, the results indicate that cis-specific local features are pivotal in maintaining and perpetuating aberrant methylation of the VHL CpG island. Contribution of some putative trans-acting factors cannot be excluded during a period when the aberrant VHL methylation pattern was first generated.
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Affiliation(s)
- I Kuzmin
- Intramural Research Support Program, SAIC-Frederick, National Cancer Institute, Frederick Cancer Research and Development Center, Frederick, Maryland, MD 21702, USA
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169
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Fujita N, Takebayashi S, Okumura K, Kudo S, Chiba T, Saya H, Nakao M. Methylation-mediated transcriptional silencing in euchromatin by methyl-CpG binding protein MBD1 isoforms. Mol Cell Biol 1999; 19:6415-26. [PMID: 10454587 PMCID: PMC84611 DOI: 10.1128/mcb.19.9.6415] [Citation(s) in RCA: 157] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
DNA methylation of promoter-associated CpG islands is involved in the transcriptional repression of vertebrate genes. To investigate the mechanisms underlying gene inactivation by DNA methylation, we characterized a human MBD1 protein, one of the components of MeCP1, which possesses a methyl-CpG binding domain (MBD) and cysteine-rich (CXXC) domains. Four novel MBD1 isoforms (MBD1v1, MBD1v2, MBD1v3, and MBD1v4) were identified by the reverse transcription-PCR method. We found that these transcripts were alternatively spliced in the region of CXXC domains and the C terminus. Green fluorescent protein-fused MBD1 was localized to multiple foci on the human genome, mostly in the euchromatin regions, and particularly concentrated in the pericentromeric region of chromosome 1. Both the MBD sequence and genome methylation were required for proper localization of the MBD1 protein. We further investigated whether MBD1 isoforms are responsible for transcriptional repression of human genes. A bacterially expressed MBD1 protein bound preferentially to methylated DNA fragments containing CpG islands from the tumor suppressor genes p16, VHL, and E-cadherin and from an imprinted SNRPN gene. All MBD1 isoforms inhibited promoter activities of these genes via methylation. Interestingly, MBD1 isoforms v1 and v2 containing three CXXC domains also suppressed unmethylated promoter activities in mammalian cells. These effects were further manifested in Drosophila melanogaster cells, which lack genome methylation. Sp1-activated transcription of methylated p16 and SNRPN promoters was inhibited by all of the MBD1 isoforms, whereas the isoforms v1 and v2 reduced Sp1-activated transcription from unmethylated promoters as well. These findings suggested that the MBD1 isoforms have different roles in methylation-mediated transcriptional silencing in euchromatin.
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Affiliation(s)
- N Fujita
- Department of Tumor Genetics and Biology, Kumamoto University School of Medicine, Kumamoto 860-0811, Japan
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170
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Tanaka M, Puchyr M, Gertsenstein M, Harpal K, Jaenisch R, Rossant J, Nagy A. Parental origin-specific expression of Mash2 is established at the time of implantation with its imprinting mechanism highly resistant to genome-wide demethylation. Mech Dev 1999; 87:129-42. [PMID: 10495277 DOI: 10.1016/s0925-4773(99)00158-6] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The Mash2 gene encodes a basic helix-loop-helix transcription factor, which is highly expressed in diploid trophoblast cells of the postimplantation mouse embryo and is required for development of the spongiotrophoblast in order to form a functional placenta. Genomic imprinting of Mash2 has been previously reported; transcriptional inactivation of the paternal wild-type allele in heterozygotes carrying a maternal null allele results in a null-equivalent embryonic lethal phenotype. In order to study the Mash2 imprinting mechanism, we have created a new allele at this locus carrying a targeted insertion of an IRES (internal ribosome entry site)-lacZ cassette within the 3' untranslated region of the gene (referred to as "Mash2-lacZ"). This new allele has made it feasible to monitor paternal Mash2 expression in a wild-type-equivalent background. Our data suggest that parental origin-specific expression of Mash2 begins in the early postimplantation conceptus (5.5 dpc) at the time when trophoblast-specific expression is observed. We also show that the paternal allele is continuously repressed up to 9.5 dpc in the developing ectoplacental cone (EPC) and early chorio-allantoic placenta, with some cells escaping paternal repression. When maternally inherited, lacZ expression from this allele reflects the expression pattern of endogenous Mash2 transcripts up to 8.5 dpc. Furthermore, we have addressed the question of a requirement for DNA methylation for the Mash2 imprinting mechanism by crossing our Mash2-lacZ mice with mice mutant for Dnmt1 (DNA-methyltransferase1). Our results show a partial loss of transcriptional repression of the paternal allele in Dnmt1 deficient background. Interestingly, however, this is not sufficient to eliminate the highly biased parental allele-specific expression of Mash2. Thus, the preferential maternal expression of the gene is still maintained in Dnmt1 null mutant embryos, although methylation analyses demonstrate that the Mash2 locus is highly demethylated in Dnmt1 null mutant embryos. The locus is also highly demythyled in wild-type EPCs. Our results suggest the possibility that a mechanism other than DNA methylation, such as allele-specific chromatin conformation, may be involved in maintenance of parental origin-specific expression of Mash2.
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Affiliation(s)
- M Tanaka
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Canada
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171
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Abstract
PURPOSE To determine: 1) If a 15q11-13 deletion was transmitted from a female with Angelman syndrome to her fetus, and 2) If the UBE3A gene was functionally imprinted in fetal eye. METHODS Individuals were genotyped by microsatellite analysis. DNA methylation imprints were assessed by Southern blot analysis and methylation-specific PCR. Expression was analyzed by RT-PCR. RESULTS The mother and fetus inherited large deletions of maternal 15q11-13 and demonstrated paternal-only DNA methylation imprints along 15q11-13. UBE3A was paternally expressed in eye tissue from the fetus with Angelman syndrome. CONCLUSIONS We show that females with Angelman syndrome are fully capable of reproduction and that UBE3A is not imprinted in fetal eye.
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Affiliation(s)
- A C Lossie
- Department of Molecular Genetics and Microbiology, and Center for Mammalian Genetics, University of Florida College of Medicine, Gainesville 32610-0296, USA
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172
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Schmidt JV, Levorse JM, Tilghman SM. Enhancer competition between H19 and Igf2 does not mediate their imprinting. Proc Natl Acad Sci U S A 1999; 96:9733-8. [PMID: 10449763 PMCID: PMC22279 DOI: 10.1073/pnas.96.17.9733] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The linked H19 and Igf2 genes on mouse distal chromosome 7 are subject to genomic imprinting. Competition between the promoters of the genes for transcription from shared enhancers has been proposed as an explanation for the coordinate expression and reciprocal imprinting of these two genes. To test this model, we have used Cre-loxP technology to generate in mice a conditional deletion of the H19 promoter and structural gene that leaves no transcription unit in the locus. Contrary to the prediction of enhancer competition we find that transcriptional activity from the H19 promoter is not required for the imprinted silencing of the Igf2 gene.
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Affiliation(s)
- J V Schmidt
- Department of Molecular Biology and The Howard Hughes Medical Institute, Princeton University, Princeton, NJ 08544, USA
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173
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Tsai TF, Jiang YH, Bressler J, Armstrong D, Beaudet AL. Paternal deletion from Snrpn to Ube3a in the mouse causes hypotonia, growth retardation and partial lethality and provides evidence for a gene contributing to Prader-Willi syndrome. Hum Mol Genet 1999; 8:1357-64. [PMID: 10400982 DOI: 10.1093/hmg/8.8.1357] [Citation(s) in RCA: 121] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Prader-Willi syndrome (PWS) is caused by paternal deficiency of human chromosome 15q11-q13. There is conflicting evidence from human translocations regarding the direct involvement of SNRPN in the pathogenesis of PWS and it is not known if the phenotypic features result from the loss of expression of a single imprinted gene or multiple genes. In an attempt to dissect genotype/phenotype correlations for the homologous region of mouse chromosome 7C, we prepared three mutant genotypes: (i) mice with a deletion of Snrpn exon 2, which removes a portion of a small, upstream open reading frame (ORF); (ii) mice with double targeting for Snrpn exon 2 and Ube3a; (iii) mice deleted from Snrpn to Ube3a, removing coding exons for both loci and intervening genes. Mice deleted for Snrpn exon 2 have no obvious phenotypic abnormalities and switching of the genomic imprint for the region is conserved. Mice carrying the Snrpn - Ube3a deletion on the paternal chromosome showed severe growth retardation, hypotonia and approximately 80% lethality before weaning. The surviving mice were fertile and were not obese up to 14 months of age. The deletion was transmitted for multiple generations and continued to cause partial lethality when inherited paternally, but not when inherited maternally. The normal imprinted expression and methylation patterns of necdin, a gene outside the deletion region, indicate that the deletion is not an imprinting mutation. The data suggest the presence of a paternally expressed structural gene between Snrpn and Ipw whose deficiency causes lethality, although other possibilities exist, including position effects on expression of imprinted genes or that simultaneous deficiency of both ORFs of Snrpn causes lethality.
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Affiliation(s)
- T F Tsai
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
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174
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Affiliation(s)
- B Horsthemke
- Institut für Humangenetik, Universitätsklinikum Essen, Germany
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175
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Affiliation(s)
- B Tycko
- Department of Pathology, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA
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176
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Gray TA, Saitoh S, Nicholls RD. An imprinted, mammalian bicistronic transcript encodes two independent proteins. Proc Natl Acad Sci U S A 1999; 96:5616-21. [PMID: 10318933 PMCID: PMC21909 DOI: 10.1073/pnas.96.10.5616] [Citation(s) in RCA: 133] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Polycistronic transcripts are common in prokaryotes but rare in eukaryotes. Phylogenetic analysis of the SNRPN (SmN) mRNA in five eutherian mammals reveals a second highly conserved coding sequence, termed SNURF (SNRPN upstream reading frame). The vast majority of nucleotide substitutions in SNURF occur in the wobble codon position, providing strong evolutionary evidence for selection for protein-coding function. Because SNURF-SNRPN maps to human chromosome 15q11-q13 and is paternally expressed, each cistron is a candidate for a role in the imprinted Prader-Willi syndrome (PWS) and PWS mouse models. SNURF encodes a highly basic 71-aa protein that is nuclear-localized (as is SmN). Because SNURF is the only protein-coding sequence within the imprinting regulatory region in 15q11-q13, it may have provided the original selection for imprinting in this domain. Whereas some human tissues express a minor SNURF-only transcript, mouse tissues express only the bicistronic Snurf-Snrpn transcript. We show that both SNURF and SNRPN are translated in normal, but not PWS, human, and mouse tissues and cell lines. These findings identify SNURF as a protein that is produced along with SmN from a bicistronic transcript; polycistronic mRNAs therefore are encoded in mammalian genomes where they may form functional operons.
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Affiliation(s)
- T A Gray
- Department of Genetics, Case Western Reserve University School of Medicine and Center for Human Genetics, University Hospitals of Cleveland, OH 44106, USA
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177
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Muralidhar B, Marney A, Butler MG. Analysis of imprinted genes in subjects with Prader-Willi syndrome and chromosome 15 abnormalities. Genet Med 1999; 1:141-5. [PMID: 11258349 PMCID: PMC6744832 DOI: 10.1097/00125817-199905000-00005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
PURPOSE To determine gene expression of five imprinted genes or transcripts from the 15q11-q13 chromosome region using reverse transcription polymerase chain reaction (RT-PCR) in a relatively large survey of Prader-Willi syndrome (PWS) and control subjects with several different chromosome 15 abnormalities. METHODS RT-PCR was undertaken on mRNA isolated from tissue (e.g., mostly lymphoblasts) from 38 PWS and 10 control subjects. DNA primers were used for five imprinted genes or transcripts (ZNF127, SNRPN, PAR5, IPW, and PAR1) from 15q11-q13 and fibrillin, a control gene from 15q21. RESULTS One PWS subject with maternal disomy 15 showed weak but detectable expression of PAR1, whereas SNRPN expression was detected in two PWS subjects [one with the 15q11-q13 deletion and one with a t(15;15) karyotype and maternal disomy 15], and the remaining typical PWS subjects showed no expression of the imprinted genes or transcripts. CONCLUSION No obvious clinical differences were identified in those PWS subjects with weak expression of genes compared with those showing no expression. Although the reason(s) for weak expression is unknown, possible explanations include relaxation of imprinting caused by failure to reset the imprinted genes or transcripts in the maternal germ line or by postzygotic gene expression or undetected chromosome 15 mosaicism in the deletion PWS subjects. The timing, tissue source, and other factors relating to partial expression of genes that are thought to be imprinted may play a role in clinical variability and allow for a better understanding of molecular mechanisms in PWS and other abnormalities of proximal chromosome 15q.
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Affiliation(s)
- B Muralidhar
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee, USA
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178
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Jong MT, Gray TA, Ji Y, Glenn CC, Saitoh S, Driscoll DJ, Nicholls RD. A novel imprinted gene, encoding a RING zinc-finger protein, and overlapping antisense transcript in the Prader-Willi syndrome critical region. Hum Mol Genet 1999; 8:783-93. [PMID: 10196367 DOI: 10.1093/hmg/8.5.783] [Citation(s) in RCA: 167] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
We describe a complex imprinted locus in chromosome 15q11-q13 that encodes two genes, ZNF127 and ZNF127AS. The ZNF127 gene encodes a protein with a RING (C3HC4) zinc-finger and multiple C3H zinc-finger motifs, the former being closely related to a protein from variola major virus, the smallpox etiological agent. These motifs allow prediction of ZNF127 function as a ribonucleoprotein. The intronless ZNF127 gene is expressed ubiquitously, but the entire coding sequence and 5' CpG island overlaps a second gene, ZNF127AS, that is transcribed from the antisense strand with a different transcript size and pattern of expression. Allele-specific analysis shows that ZNF127 is expressed only from the paternal allele. Consistent with this expression pattern, in the brain the ZNF127 5' CpG island is completely unmethylated on the paternal allele but methylated on the maternal allele. Analyses of adult testis, sperm and fetal oocytes demonstrates a gametic methylation imprint with unmethylated paternal germ cells. Recent findings indicate that ZNF127 is part of the coordinately regulated imprinted domain affected in Prader-Willi syndrome patients with imprinting mutations. Therefore, ZNF127 and ZNF127AS are novel imprinted genes that may be associated with some of the clinical features of the polygenic Prader-Willi syndrome.
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Affiliation(s)
- M T Jong
- Department of Genetics and Center for Human Genetics, Case Western Reserve University School of Medicine, University Hospitals of Cleveland, 10900 Euclid Avenue, Cleveland, OH 44106-4955, USA
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179
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Schweizer J, Zynger D, Francke U. In vivo nuclease hypersensitivity studies reveal multiple sites of parental origin-dependent differential chromatin conformation in the 150 kb SNRPN transcription unit. Hum Mol Genet 1999; 8:555-66. [PMID: 10072422 DOI: 10.1093/hmg/8.4.555] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Human chromosome region 15q11-q13 contains a cluster of oppositely imprinted genes. Loss of the paternal or the maternal alleles by deletion of the region or by uniparental disomy 15 results in Prader-Willi syndrome (PWS) or Angelman syndrome (AS), respectively. Hence, the two phenotypically distinct neurodevelopmental disorders are caused by the lack of products of imprinted genes. Subsets of PWS and AS patients exhibit 'imprinting mutations', such as small microdeletions within the 5' region of the small nuclear ribonucleoprotein polypeptide N ( SNRPN ) transcription unit which affect the transcriptional activity and methylation status of distant imprinted genes throughout 15q11-q13 in cis. To elucidate the mechanism of these long-range effects, we have analyzed the chromatin structure of the 150 kb SNRPN transcription unit for DNase I- and Msp I-hypersensitive sites. By using an in vivo approach on lymphoblastoid cell lines from PWS and AS individuals, we discovered that the SNRPN exon 1 is flanked by prominent hypersensitive sites on the paternal allele, but is completely inaccessible to nucleases on the maternal allele. In contrast, we identified several regions of increased nuclease hypersensitivity on the maternal allele, one of which coincides with the AS minimal microdeletion region and another lies in intron 1 immediately downstream of the paternal-specific hypersensitive sites. At several sites, parental origin-specific nuclease hypersensitivity was found to be correlated with hypermethylation on the allele contributed by the other parent. The differential parental origin-dependent chromatin conformations might govern access of regulatory protein complexes and/or RNAs which could mediate interaction of the region with other genes.
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Affiliation(s)
- J Schweizer
- Howard Hughes Medical Institute and Department of Genetics, Stanford University School of Medicine, Stanford CA 94305-5323, USA
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180
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Khan NL, Wood NW. Prader-Willi and Angelman syndromes: update on genetic mechanisms and diagnostic complexities. Curr Opin Neurol 1999; 12:149-54. [PMID: 10226746 DOI: 10.1097/00019052-199904000-00004] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Significant advances have been made in determining the genetic basis of the Prader-Willi and Angelman syndromes; disorders in which genomic imprinting is abnormal. These advances will be instrumental in unravelling the pathogenesis that underlies these neurobehavioural disorders.
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Affiliation(s)
- N L Khan
- Department of Clinical Neurology, Institute of Neurology, London, UK
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181
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Abstract
A small number of mammalian genes undergo the process of genomic imprinting whereby the expression level of the alleles of a gene depends upon their parental origin. In the past year, attention has focused on the mechanisms that determine parental-specific expression patterns. Many imprinted genes are located in conserved clusters and, although it is apparent that imprinting of adjacent genes is jointly regulated, multiple mechanisms among and within clusters may operate. Recent developments have also refined the timing of the gametic imprints and further defined the mechanism by which DNA methyltransferases confer allelic methylation patterns.
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Affiliation(s)
- C I Brannan
- Department of Molecular Genetics and Microbiology, The Center for Mammalian Genetics, University of Florida Brain Institute, University of Florida College of Medicine, Gainesville, Florida 32610, USA
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182
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Lee MP, Brandenburg S, Landes GM, Adams M, Miller G, Feinberg AP. Two novel genes in the center of the 11p15 imprinted domain escape genomic imprinting. Hum Mol Genet 1999; 8:683-90. [PMID: 10072438 DOI: 10.1093/hmg/8.4.683] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
We previously reported the isolation of a 2.5 Mb tumor-suppressing subchromosomal transferable fragment (STF) from human chromosome 11p15 and the identification of nine known genes and four novel genes within this STF. We now report the isolation of two novel cDNAs, designated here as TSSC4 and TSSC6 (tumor-suppressing STF cDNA 4 and 6), located within the STF. TSSC4 and TSSC6 encode predicted proteins of 329 and 290 amino acids, respectively, with no close similarity to previously reported proteins. TSSC4 and TSSC6 are both located in the center of a 1 Mb imprinted domain, which contains the imprinted genes TSSC3, TSSC5, p57(KIP2), KVLQT1, ASCL2, IGF2 and H19. However, we found that neither TSSC4 nor TSSC6 was significantly imprinted in any of the fetal or extra-embryonic tissues examined. Based on this result, the imprinted gene domain of 11p15 appears to contain at least two imprinted subdomains, between which TSSC4 and TSSC6 substantially escape imprinting, due either to lack of initial silencing or to an early developmental relaxation of imprinting.
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Affiliation(s)
- M P Lee
- Department of Medicine, Johns Hopkins University School of Medicine, 1064 Ross, 720 Rutland Avenue, Baltimore, MD 21205, USA
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183
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Falls JG, Pulford DJ, Wylie AA, Jirtle RL. Genomic imprinting: implications for human disease. THE AMERICAN JOURNAL OF PATHOLOGY 1999; 154:635-47. [PMID: 10079240 PMCID: PMC1866410 DOI: 10.1016/s0002-9440(10)65309-6] [Citation(s) in RCA: 269] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 01/06/1999] [Indexed: 01/14/2023]
Abstract
Genomic imprinting refers to an epigenetic marking of genes that results in monoallelic expression. This parent-of-origin dependent phenomenon is a notable exception to the laws of Mendelian genetics. Imprinted genes are intricately involved in fetal and behavioral development. Consequently, abnormal expression of these genes results in numerous human genetic disorders including carcinogenesis. This paper reviews genomic imprinting and its role in human disease. Additional information about imprinted genes can be found on the Genomic Imprinting Website at http://www.geneimprint.com.
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Affiliation(s)
- J G Falls
- Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina27710, USA
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184
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Mohandas T, Park JP, Spellman RA, Filiano JJ, Mamourian AC, Hawk AB, Belloni DR, Noll WW, Moeschler JB. Paternally derived de novo interstitial duplication of proximal 15q in a patient with developmental delay. ACTA ACUST UNITED AC 1999. [DOI: 10.1002/(sici)1096-8628(19990212)82:4<294::aid-ajmg4>3.0.co;2-u] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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185
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Ohta T, Gray TA, Rogan PK, Buiting K, Gabriel JM, Saitoh S, Muralidhar B, Bilienska B, Krajewska-Walasek M, Driscoll DJ, Horsthemke B, Butler MG, Nicholls RD. Imprinting-mutation mechanisms in Prader-Willi syndrome. Am J Hum Genet 1999; 64:397-413. [PMID: 9973278 PMCID: PMC1377750 DOI: 10.1086/302233] [Citation(s) in RCA: 214] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
Microdeletions of a region termed the "imprinting center" (IC) in chromosome 15q11-q13 have been identified in several families with Prader-Willi syndrome (PWS) or Angelman syndrome who show epigenetic inheritance for this region that is consistent with a mutation in the imprinting process. The IC controls resetting of parental imprints in 15q11-q13 during gametogenesis. We have identified a larger series of cases of familial PWS, including one case with a deletion of only 7.5 kb, that narrows the PWS critical region to <4. 3 kb spanning the SNRPN gene CpG island and exon 1. Identification of a strong DNase I hypersensitive site, specific for the paternal allele, and six evolutionarily conserved (human-mouse) sequences that are potential transcription-factor binding sites is consistent with this region defining the SNRPN gene promoter. These findings suggest that promoter elements at SNRPN play a key role in the initiation of imprint switching during spermatogenesis. We also identified three patients with sporadic PWS who have an imprinting mutation (IM) and no detectable mutation in the IC. An inherited 15q11-q13 mutation or a trans-factor gene mutation are unlikely; thus, the disease in these patients may arise from a developmental or stochastic failure to switch the maternal-to-paternal imprint during parental spermatogenesis. These studies allow a better understanding of a novel mechanism of human disease, since the epigenetic effect of an IM in the parental germ line determines the phenotypic effect in the patient.
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Affiliation(s)
- T Ohta
- Department of Genetics, Case Western Reserve University School of Medicine, and Center for Human Genetics, University Hospitals of Cleveland, OH 44106-4955, USA
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186
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Abstract
One of the major discoveries in modern genetics is the phenomenon of genomic, or parental, imprinting. The parent-of-origin effects seen after transmission of an imprinted gene from parents to their children do not follow the genetic rules postulated by Gregor Mendel. This has obvious consequences for genetic counselling. Aberrant imprinting can lead to a wide variety of clinical disorders ranging from the development of tumours to pronounced growth abnormalities and from mental retardation to developmental disorders of language or autism as seen in Turner's syndrome. Here we describe the basic principles of genomic imprinting and discuss a number of well-characterized clinical disorders associated with genomic imprinting.
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Affiliation(s)
- M Mannens
- Department of Clinical Genetics, Academic Medical Centre, University of Amsterdam, The Netherlands.
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187
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Abstract
Genomic imprinting in mammals results in the differential expression of maternal and paternal alleles of certain genes. Recent observations have revealed that the regulation of imprinted genes is only partially determined by epigenetic modifications imposed on the two parental genomes during gametogenesis. Additional modifications mediated by factors in the ooplasm, early embryo, or developing embryonic tissues appear to be involved in establishing monoallelic expression for a majority of imprinted genes. As a result, genomic imprinting effects may be manifested in a stage-specific or cell type-specific manner. The developmental aspects of imprinting are reviewed here, and the available molecular data that address the mechanism of allele silencing for three specific imprinted gene domains are considered within the context of explaining how the imprinted gene silencing may be controlled developmentally.
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Affiliation(s)
- K E Latham
- Fels Institute for Cancer Research and Molecular Biology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140, USA
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188
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Kuslich CD, Kobori JA, Mohapatra G, Gregorio-King C, Donlon TA. Prader-Willi syndrome is caused by disruption of the SNRPN gene. Am J Hum Genet 1999; 64:70-6. [PMID: 9915945 PMCID: PMC1377704 DOI: 10.1086/302177] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
A Prader-Willi syndrome patient is described who has a de novo balanced translocation, (4;15)(q27;q11.2)pat, with breakpoints lying between SNRPN exons 2 and 3. Parental-origin studies indicate that there is no uniparental disomy and no apparent deletion. This patient expresses ZNF127, SNRPN exons 1 and 2, IPW, and D15S227E (PAR1) but does not express either SNRPN exons 3 and 4 or D15S226E (PAR5), as assayed by reverse transcription-PCR, of peripheral blood cells. Methylation studies showed normal biparental patterns of inheritance of loci DN34/ZNF127, D15S63, and SNRPN exon 1. Results for this patient and that reported by Sun et al. support the contention that an intact genomic region and/or transcription of SNRPN exons 2 and 3 play a pivotal role in the manifestations of the major clinical phenotype in Prader-Willi syndrome.
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Affiliation(s)
- C D Kuslich
- Molecular Cytogenetics Laboratory, Kapiolani Health Research Institute, Honolulu, HI 96816-0923.
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189
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Gabriel JM, Higgins MJ, Gebuhr TC, Shows TB, Saitoh S, Nicholls RD. A model system to study genomic imprinting of human genes. Proc Natl Acad Sci U S A 1998; 95:14857-62. [PMID: 9843980 PMCID: PMC24540 DOI: 10.1073/pnas.95.25.14857] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Somatic-cell hybrids have been shown to maintain the correct epigenetic chromatin states to study developmental globin gene expression as well as gene expression on the active and inactive X chromosomes. This suggests the potential use of somatic-cell hybrids containing either a maternal or a paternal human chromosome as a model system to study known imprinted genes and to identify as-yet-unknown imprinted genes. Testing gene expression by using reverse transcription followed by PCR, we show that functional imprints are maintained at four previously characterized 15q11-q13 loci in hybrids containing a single human chromosome 15 and at two chromosome 11p15 loci in hybrids containing a single chromosome 11. In contrast, three gamma-aminobutyric acid type A receptor subunit genes in 15q12-q13 are nonimprinted. Furthermore, we have found that differential DNA methylation imprints at the SNRPN promoter and at a CpG island in 11p15 are also maintained in somatic-cell hybrids. Somatic-cell hybrids therefore are a valid and powerful system for studying known imprinted genes as well as for rapidly identifying new imprinted genes.
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Affiliation(s)
- J M Gabriel
- Department of Genetics, Case Western Reserve University School of Medicine, University Hospitals of Cleveland, 10900 Euclid Avenue, Cleveland, OH 44106-4955, USA
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190
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Saitoh S, Buiting K, Cassidy SB, Conroy JM, Driscoll DJ, Gabriel JM, Gillessen-Kaesbach G, Glenn CC, Greenswag LR, Horsthemke B, Kondo I, Kuwajima K, Niikawa N, Rogan PK, Schwartz S, Seip J, Williams CA, Nicholls RD. Clinical spectrum and molecular diagnosis of Angelman and Prader-Willi syndrome patients with an imprinting mutation. ACTA ACUST UNITED AC 1998. [DOI: 10.1002/(sici)1096-8628(19970120)68:2<195::aid-ajmg15>3.0.co;2-p] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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191
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Abstract
Six patients from the clinical cytogenetics laboratory identified as having the normal variant dup(15)(q12) were further evaluated using fluorescence in situ hybridization (FISH). The purpose of this study was to ascertain whether any of the Prader Willi Angelman Chromosome Region (PWCR and ANCR, respectively) loci were duplicated in these patients. The results indicated that the patients could be categorized into two groups. The first group showed no duplication of the PWCR ANCR loci and appeared to belong to the dup(15)(q12) class which is phenotypically silent and is therefore called the normal variant. The second group also showed no duplication of the PWCR/ANCR loci. but had a large alpha satellite variant with D15Z. It is hypothesized that these patients do not have a duplication of 15q12 but rather a centromeric variant which mimics the dup(15)(q12). This study confirms the importance of evaluating apparent variations in the proximal region of chromosome 15 with FISH.
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Affiliation(s)
- D Riordan
- Division of Laboratory Medicine and Pathology, Health Sciences Center, University of Manitoba, Winnipeg, Canada
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192
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Clarke D, Boer H, Webb T, Scott P, Frazer S, Vogels A, Borghgraef M, Curfs LM. Prader-Willi syndrome and psychotic symptoms: 1. Case descriptions and genetic studies. JOURNAL OF INTELLECTUAL DISABILITY RESEARCH : JIDR 1998; 42 ( Pt 6):440-450. [PMID: 10030439 DOI: 10.1046/j.1365-2788.1998.4260440.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Six people with Prader-Willi syndrome (PWS) who developed psychoses are described. Along with other literature reviewed in the present paper, the results imply an association between PWS and psychotic symptoms. Genetic studies were possible in five cases and SNRPN expression was examined in three cases. Maternal uniparental disomy and 15q11q13 deletions were found, demonstrating that psychotic symptoms are not associated with a single type of genetic abnormality.
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Affiliation(s)
- D Clarke
- Department of Psychiatry, University of Birmingham, UK
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193
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194
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Monaghan KG, Van Dyke DL, Feldman GL. Prader-Willi-like syndrome in a patient with an Xq23q25 duplication. AMERICAN JOURNAL OF MEDICAL GENETICS 1998; 80:227-31. [PMID: 9843044 DOI: 10.1002/(sici)1096-8628(19981116)80:3<227::aid-ajmg10>3.0.co;2-q] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We report on a 24-year old woman with an Xq duplication and findings suggestive of Prader-Willi syndrome (PWS). Her birth weight was at the 3rd centile and her birth length was less than the 3rd centile. She was hypotonic and had a weak cry as an infant. There were no feeding difficulties, although her mother reports that as an infant, she was "small for her age." Excessive weight gain began between 3 and 4 years. The patient's development was delayed and she received special education. She has a history of hiding food. She has a sleep disturbance disorder and inappropriate social behavior. At the age of 24 years her height was below the 5th centile and weight >>95th centile. She has physical findings typical of PWS, skin picking, and speech articulation defects. Cytogenetic analysis showed a 46,X,dup(X)(q23q25) karyotype. Fluorescent in situ hybridization (FISH) studies using a chromosome X painting probe demonstrated that the rearrangement was intrachromosomal. The X-chromosome fold scoring technique was used to determine the X inactivation pattern and indicated that some cells expressed the abnormal X chromosome. Results of FISH studies using the SNRPN probe localized to 15q11q13 and DNA studies using the PW71B and SNRPN probes were normal. The duplicated X chromosome, random X inactivation pattern, and the negative molecular studies for PWS indicate that the abnormal X chromosome is the basis of this patient's phenotype. This patient emphasizes the importance of obtaining a karyotype even when a syndrome diagnosable by molecular methods is strongly suspected.
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Affiliation(s)
- K G Monaghan
- Department of Medical Genetics, Henry Ford Hospital, Detroit, Michigan 48202, USA
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195
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Tsai TF, Raas-Rothschild A, Ben-Neriah Z, Beaudet AL. Prenatal diagnosis and carrier detection for a point mutation in UBE3A causing Angelman syndrome. Am J Hum Genet 1998; 63:1561-3. [PMID: 9792887 PMCID: PMC1377568 DOI: 10.1086/302120] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
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196
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Jiang YH, Armstrong D, Albrecht U, Atkins CM, Noebels JL, Eichele G, Sweatt JD, Beaudet AL. Mutation of the Angelman ubiquitin ligase in mice causes increased cytoplasmic p53 and deficits of contextual learning and long-term potentiation. Neuron 1998; 21:799-811. [PMID: 9808466 DOI: 10.1016/s0896-6273(00)80596-6] [Citation(s) in RCA: 634] [Impact Index Per Article: 24.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The E6-AP ubiquitin ligase (human/mouse gene UBE3A/Ube3a) promotes the degradation of p53 in association with papilloma E6 protein, and maternal deficiency causes human Angelman syndrome (AS). Ube3a is imprinted with silencing of the paternal allele in hippocampus and cerebellum in mice. We found that the phenotype of mice with maternal deficiency (m-/p+) for Ube3a resembles human AS with motor dysfunction, inducible seizures, and a context-dependent learning deficit. Long-term potentiation (LTP) was severely impaired in m-/p+ mice despite normal baseline synaptic transmission and neuroanatomy, indicating that ubiquitination may play a role in mammalian LTP and that LTP may be abnormal in AS. The cytoplasmic abundance of p53 was increased in postmitotic neurons in m-/p+ mice and in AS, providing a potential biochemical basis for the phenotype through failure to ubiquitinate and degrade various effectors.
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Affiliation(s)
- Y H Jiang
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA
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197
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Holland A. Understanding the Eating Disorder Affecting People with Prader-Willi Syndrome. JOURNAL OF APPLIED RESEARCH IN INTELLECTUAL DISABILITIES 1998. [DOI: 10.1111/j.1468-3148.1998.tb00061.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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198
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Abstract
A number of recent studies have provided new insights into mechanisms that regulate genomic imprinting in the mammalian genome. Regions of allele-specific differential methylation (DMRs) are present in all imprinted genes examined. Differential methylation is erased in germ cells at an early stage of their development, and germ-line-specific methylation imprints in DMRs are reestablished around the time of birth. After fertilization, differential methylation is retained in core DMRs despite genome-wide demethylation and de novo methylation during preimplantation and early postimplantation stages. Direct repeats near CG-rich DMRs may be involved in the establishment and maintenance of allele-specific methylation patterns. Imprinted genes tend to be clustered; one important component of clustering is enhancer competition, whereby promoters of linked imprinted genes compete for access to enhancers. Regional organization and spreading of the epigenotype during development is also important and depends on DMRs and imprinting centers. The mechanism of cis spreading of DNA methylation is not known, but precedent is provided by the Xist RNA, which results in X chromosome inactivation in cis. Reading of the somatic imprints could be carried out by transcription factors that are sensitive to methylation, or by methyl-cytosine-binding proteins that are involved in transcriptional repression through chromatin remodeling.
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Affiliation(s)
- M Constância
- Programme in Developmental Genetics, The Babraham Institute, Cambridge CB2 4AT, UK
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199
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Abstract
In some mammalian genes, paternally and maternally derived alleles are expressed differently: this phenomenon is called genomic imprinting. Several-explanations have been proposed for the observed patterns of genomic imprinting, but the most successful explanation is the genetic conflict hypothesis--natural selection operating on the gene expression produces the parental origin-dependent gene expression--because the paternally derived allele tends to be less related to the siblings of the same mother than the maternal allele and hence the paternal allele should evolve to be more aggressive in obtaining maternal resources. The successes and failures of this argument have been examined in explaining the observed patterns of genomic imprinting in mammals. After a brief summary of the observations with some examples, a quantitative genetic model describing the evolution of the cis-regulating element of a gene affecting the maternal resource acquisition was presented. The model supports the verbal argument that the growth enhancer should evolve to show imprinting with the paternal allele expressed and the maternal allele inactive, whereas a growth suppressor gene tends to have an inactive paternal allele and an active maternal allele. There are four major problems of the genetic conflict hypothesis. (1) Some genes affect embryonic growth but are not imprinted (e.g., Igf1), which can be explained by considering recessive, deleterious mutations on the coding regions, (2) A gene exists that shows the pattern that is a perfect reversal (Mash2), which is needed for placental growth, and yet has an active maternal allele and an inactive paternal allele. This can be explained if the overproduction of this gene causes dose-sensitive abortion to occur in early gestation. (3) Paternal disomies are sometimes smaller than normal embryos. This is a likely outcome of evolution if imprinted genes control the allocation between placenta and embryo by modifying the cell developmental fate. (4) Genes on X chromosomes do not follow the predictions of the genetic conflict hypothesis. For genes on X chromosomes, two additional forces of natural selection (sex differentiation and dosage compensation) cause genomic imprinting, possibly in the opposite direction. Available evidence suggests that these processes are stronger than the natural selection caused by female multiple mating. Finally, the same formalism of evolution can handle an alternative nonconflict hypothesis: genomic imprinting might have evolved because it reduces the risk of the spontaneous development of parthenogenetic embryo, causing a serious threat to the life of the mother (ovarian time bomb hypothesis). This hypothesis can also explain major patterns of genomic imprinting. In conclusion, the genetic conflict hypothesis is very successful in explaining the observed patterns of imprinting for autosomal genes and probably is the most likely evolutionary explanation for them. However, for genes on X chromosomes, other processes of natural selection are more important. Considering that a nonconflict hypothesis can also explain the patterns in principle, we need a quantitative estimate of various parameters, such as the rate of dose-dependent abortion, the degree of female promiscuity, and the rate of spontaneous development of the parthenogenetic embryo, in order to make judgments on the relative importance of different forces of natural selection to form genomic imprinting.
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Affiliation(s)
- Y Iwasa
- Department of Biology, Faculty of Science, Kyushu University, Fukuoka, Japan
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200
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Malzac P, Moncla A, Pedeillier K, Vo Van C, Girardot L, Voelckel MA. Atypical molecular findings identify limits of technical screening tests for Prader-Willi and Angelman syndrome diagnoses. AMERICAN JOURNAL OF MEDICAL GENETICS 1998; 78:242-4. [PMID: 9677058 DOI: 10.1002/(sici)1096-8628(19980707)78:3<242::aid-ajmg6>3.0.co;2-r] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- P Malzac
- Département de Génétique Médicale, Hôpital d'Enfants de la Timone, Marseille, France
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