Multiple genetic loci within 11p15 defined by Beckwith-Wiedemann syndrome rearrangement breakpoints and subchromosomal transferable fragments.

Abstract

Beckwith-Wiedemann syndrome (BWS) involves fetal overgrowth and predisposition to a wide variety of embryonal tumors of childhood. We have previously found that BWS is genetically linked to llpl5 and that this same band shows loss of heterozygosity in the types of tumors to which children with BWS are susceptible. However, llpl5 contains >20 megabases, and therefore, the BWS and tumor suppressor genes could be distinct. To determine the precise physical relationship between these loci, we isolated yeast artificial chromosomes, and cosmid libraries from them, within the region of loss of heterozygosity in embryonal tumors. Five germ-line balanced chromosomal rearrangement breakpoint sites from BWS patients, as well as a balanced chromosomal translocation breakpoint from a rhabdoid tumor, were isolated within a 295-to 320-kb cluster defined by a complete cosmid contig crossing these breakpoints. This breakpoint cluster terminated approximately 100 kb centromeric to the imprinted gene IGF2 and 100 kb telomeric to p57KIP2, an inhibitor of cyclin-dependent kinases, and was located within subchromosomal transferable fragments that suppressed the growth of embryonal tumor cells in genetic complementation experiments. We have identified 11 transcribed sequences in this BWS/tumor suppressor coincident region, one of which corresponded to p57KIP2. However, three additional BWS breakpoints were >4 megabases centromeric to the other five breakpoints and were excluded from the tumor suppressor region defined by subchromosomal transferable fragments. Thus, multiple genetic loci define BWS and tumor suppression on llpl5. refs. 5 and 6) and the closely linked H19 (5, 7), are imprinted, i.e., show parental origin-specific gene expression in normalThe publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.development. Furthermore, IGF2 shows loss of imprinting in embryonal tumors (5,6,8,9).The simplest hypothesis is that a single gene accounts for BWS and embryonal tumors and that balanced germ-line chromosomal rearrangements from BWS patients interrupt and, therefore, define this gene. Sait et al. (10) indirectly mapped by pulse field gel electrophoresis (PFGE) three such BWS breakpoints to a 675-kb region of ilpiS and >275 kb centromeric to IGF2. However, this distance is tentative as it was derived from the sum of several PFGE fragments, one of which was inferred from other larger overlapping PFGE fragments. Furthermore, two BWS breakpoints lie at an undetermined distance centromeric to these PFGE fragments (11). In these mapping studies, only one breakpoint has been isolated (10), and thus the precise physical relationship among them is unknown. Furthermore, indirect mapping by PFGE is limited by the large size of the fragments. Finally, the relationship between any of these breakpoints and a tumor suppressor gene on llpiS has not been determined.We cloned the region of ...

Expression and parental imprinting of the H19 gene in human rhabdomyosarcoma

“…) (Hoovers et al, 1995) and telomeric (HRAS) (van Heyningen and Little, 1995) to the IGF-2/H19 region were observed in these RMS samples (data not shown). These results are compatible with the accompanying loss of maternal 11p15 alleles and duplication of the corresponding paternal alleles in these ®ve RMSs.…”

Allelotype of pediatric rhabdomyosarcoma

“…Recently in two out of nine BeckwithWiedemann syndrome (BWS) patients, who have a high susceptibility for WT and RMS, mutations were found in p57 kip2 (Hatada et al, 1996b). However, in an earlier study ®ve breakpoints in BWS patients have been mapped on chromosome 11p15.5, together with the breakpoint of a rhabdoid tumor cell line (Hoovers et al, 1995;Newsham et al, 1994). These breakpoints do not a ect the structure of the p57 kip2 gene.…”

Human p57KIP2 defines a new imprinted domain on chromosome 11p but is not a tumour suppressor gene in Wilms tumour

“…A more parsimonious explanation involves mosaic expression in dierent cell types from either the maternal or paternal allele in a manner similar to the mechanism of allelic silencing that occurs during allelic exclusion. p57 KIP2 is located approximately 400 kb from IGF2 (Hoovers et al, 1995), and the question of whether H19, IGF2 and p57 KIP2 form part of a coordinately regulated domain was investigated by quantifying the levels of p57 KIP2 transcription in Wilms tumours that had reversed the H19/IGF2 imprint on the maternal chromosome. As the result of an epigenetic alteration, the maternal H19 allele was not transcribed in these tumours and IGF2 was biallelically expressed.…”