Replication asynchrony between homologs 15q11.2: Cytogenetic evidence for genomic imprinting
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Replication kinetics of the Prader-Willi syndrome critical region (15q11.2) was investigated in seven normal healthy adult females using RBG replication bands. Replication asynchrony between homologs 15q11.2 was identified consistently in about 40% of cells in all individuals. It was limited to the stages in which Xp22, Xp11, Xq13 and Xq24/26 were visible in the late-replicating X chromosome. This asynchrony suggested that replication timing overlapped between 15q11.2 and the early replicating R-bands of the late X chromosome in some cells, and that the difference in replication timing between homologs was probably related to genomic imprinting; the latter has been suggested as a pathogenetic basis of Prader-Willi syndrome. As a result of an analysis of the proportions of asynchronous and synchronous cells in each replication stage, two types of cells were deduced providing 1∶1 methylation mosaicism of genomic imprinting was assumed. The first type was composed of cells with normal replication in one homolog and delayed replication in the other. The second type was composed of cells with normal replication in both homologs. Our results provide cytogenetic evidence of methylation mosaicism for mammalian genomic imprinting.
KeywordsInternal Medicine Metabolic Disease Adult Female Critical Region Healthy Adult Female
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- Beechey CV, Cattanach BM, Searle AG (1989) Genetic imprinting map. Mouse News Lett 84:48–49Google Scholar
- Butler MG, Palmer CG (1983) Parental origin of chromosome 15 deletion in Prader-Willi syndrome. Lancet I:1285–1286Google Scholar
- Cassidy SB (1984) Prader-Willi syndrome. Curr Probl Pediatr 14:1–55Google Scholar
- German JL (1962) DNA synthesis in human chromosomes. Trans NY Acad Sci 24:395–407Google Scholar
- Ikeuchi Y, Sasaki M (1979) Accumulation of early mitotic cells in ethidium bromide-treated human lymphocyte cultures. Proc Jpn Acad 55B:15–18Google Scholar
- Riggs AD (1990) DNA methylation and late replication probably aid cell memory, and type I DNA reeling could aid chromosome folding and enhancer function. Philos Trans R Soc Lond [Biol] 326:285–297Google Scholar
- Silva AJ, White R (1988) Inheritance of allelic blueprints for methylation patterns. Cell 54:142–152Google Scholar