Molecular characterization of Beckwith-Wiedemann syndrome (BWS) patients with partial duplication of chromosome 11p excludes the gene MYOD1 from the BWS region

The molecular characterization of two patients with features of Beckwith-Wiedemann syndrome (BWS) and chromosome abnormalities is consistent with the association of this phenotype with a duplication of a portion of chromosome 11. Quantitative Southern blot analysis of DNA from patient A defines a large inherited duplicated segment of chromosome 11. For patient B, a de novo duplication of unknown origin has been shown to contain a segment of 11p15. This chromosome segment includes the genes for insulin-like growth factor 2, beta-hemoglobin, calcitonin A (CALCA), and parathyroid hormone (PTH). However, the myogenic differentiation factor, MYOD1, is not included in the duplicated segment. This demonstrates that MYOD1 is proximal to CALCA and PTH and excludes MYOD1 as the BWS gene. These data place the BWS gene distal to MYOD1 on 11p15.     

Loss of alleles on the short arm of chromosome 11 in a hepatoblastoma from a child with Beckwith-Wiedemann syndrome

Summary The Beckwith-Wiedemann syndrome (BWS) is characterised by multiple congenital abnormalities, including exomphalos, macroglossia, and gigantism. It is also associated with an elevated risk of embryonal neoplasia and occasionally with constitutional anomalies of chromosome band 11p15. A common pathogenetic mechanism for the development of several embryonal tumours has been proposed involving the loss of somatic heterozygosity for a locus on the short arm of chromosome 11. In support of this hypothesis, we have recently reported generation of homozygosity for the c-Ha-ras-1 protooncogene in an adrenal adenoma from an adult BWS patient. In this study wer report the generation of homozygosity for a region on the short arm of chromosome 11 defined by the calcitonin (11p13-15) and insulin (11p15-15.1) genes in a hepatoblastoma from a child with BWS.     

New p57KIP2 mutations in Beckwith-Wiedemann syndrome

Beckwith-Wiedemann syndrome (BWS) is characterized by numerous growth abnormalities and an increased risk of childhood tumors. The gene for BWS is localized in the 11p15.5 region, as determined by linkage analysis of autosomal dominant pedigrees. The increased maternal transmission pattern seen in the autosomal dominant-type pedigrees and the findings of paternal uniparental disomy reported for a subgroup of patients indicate that the gene for BWS is imprinted. Previously, we found p57 ^KIP2 , which is a Cdk-kinase inhibitor located at 11p15, is mutated in two BWS patients. Here, we screened for the mutation of the gene in 15 BWS patients. Received: 25 March 1997 / Accepted: 22 May 1997     

Assessment of p57(KIP2) gene mutation in Beckwith-Wiedemann syndrome

Beckwith-Wiedemann syndrome (BWS) is an overgrowth disorder involving developmental anomalies, tissue and organ hyperplasia and an increased risk of embryonic tumours (most commonly Wilms' tumour). This multigenic disorder is caused by dysregulation of the expression of imprinted genes in the 11p15 chromosomal region. It may involve paternal uniparental disomy (UPD), loss of imprinting of the IGF2 gene, maternal inherited translocations and trisomy with paternal duplication. Recently, a small proportion of BWS patients has been shown to have a mutation in the paternal imprinted p57(KIP2) gene, which encodes a cyclin-dependent kinase inhibitor and negatively regulates cell proliferation. We screened for p57(KIP2) gene mutations in 21 BWS patients with no 11p15 UPD in leucocyte DNA. All patients had a phenotype typical of BWS. We analysed the entire coding sequence of p57(KIP2), including intron-exon boundaries, by direct sequencing of five PCR-amplified fragments. No mutation was found in the p57(KIP2) gene. Our results are consistent with those of previous studies showing that mutation of p57(KIP2) is infrequent in BWS. Thus, other mechanisms of p57(KIP2) silencing (imprinting errors) and/or other 11p15 genes are probably involved in the pathogenesis of BWS.     

Microdeletion of LIT1 in familial Beckwith-Wiedemann syndrome

Beckwith-Wiedemann syndrome (BWS), which causes prenatal overgrowth, midline abdominal wall defects, macroglossia, and embryonal tumors, is a model for understanding the relationship between genomic imprinting, human development, and cancer. The causes are heterogeneous, involving multiple genes on 11p15 and including infrequent mutation of p57(KIP2) or loss of imprinting of either of two imprinted gene domains on 11p15: LIT1, which is near p57(KIP2), or H19/IGF2. Unlike Prader-Willi and Angelman syndromes, no chromosomal deletions have yet been identified. Here we report a microdeletion including the entire LIT1 gene, providing genetic confirmation of the importance of this gene region in BWS. When inherited maternally, the deletion causes BWS with silencing of p57(KIP2), indicating deletion of an element important for the regulation of p57(KIP2) expression. When inherited paternally, there is no phenotype, suggesting that the LIT1 RNA itself is not necessary for normal development in humans.     

11p15.5-specific libraries for identification of potential gene sequences involved in Beckwith-Wiedemann syndrome and tumorigenesis.

Constitutional and somatic chromosomal abnormalities of the chromosome 11p15 region are involved in an overgrowth malformation syndrome, the Beckwith-Wiedemann syndrome (BWS), and in several types of associated tumors. The bias in parental origin for the different etiologic forms of this syndrome and for loss of heterozygosity in the tumors suggests that a gene (or genes) mapping to this region undergoes genomic imprinting. However, the precise localization of the locus (or loci) for the BWS and associated tumors is still unknown and more markers are required. We therefore isolated 11p15 markers from two libraries: the first one obtained by microdissection of the chromosome 11p15.5 region and the second one, a phage library, constructed from a hybrid cell line containing this region as its sole human DNA. Of 19 microclones isolated from the microdissection library, 11 were evolutionarily conserved. Four phage clones were isolated; one (D11S774) detected a highly informative variable number of tandem repeats (VNTR) and another (D11S773) a biallelic polymorphism. These clones were sublocalized using a panel of somatic cell hybrids that defines eight physical intervals in 11p15.5. Twenty-one clones map to the distal interval that harbors the BWS locus.     

Beckwith-Wiedemann syndrome: multiple molecular mechanisms

Beckwith-Wiedemann syndrome (BWS) is a congenital overgrowth condition with an increased risk of developing embryonic tumours, such as Wilms' tumour. The cardinal features are abdominal wall defects, macroglossia and gigantism. BWS is generally sporadic; only 10-15% of cases are familial. A variety of molecular aberrations have been associated with BWS. The only mutations within a gene are loss-of-function mutations in the CDKN1C gene, which codes for an imprinted cell-cycle regulator. CDKN1C mutations appear to be particularly associated with umbilical abnormalities, but not with increased predisposition to Wilms' tumour. In the remaining BWS subgroups, a disturbance of the tight epigenetic regulation of gene expression (patUPD 11p, microdeletions or epimutations) seems to be the cause of the syndrome. Here we describe the clinical presentation of BWS and its dissociation from phenotypically overlapping overgrowth syndromes. We then review the current concepts of causative molecular genetic and epigenetic mechanisms, and discuss future directions of research.     

Molecular definition of the 11p15.5 region involved in Beckwith-Wiedemann syndrome and probably in predisposition to adrenocortical carcinoma

Summary To define more precisely, in molecular terms, the region involved in Beckwith-Wiedemann syndrome (BWS), we have studied patients with BWS and a constitutional duplication of 11p15 using eight 11p15 markers. In the first case with a de novo duplication and extra material on 11p, the region spanning pter to CALCA, excluded, was duplicated. In the second case, the rearrangement was characterized using somatic cell hybrids established with lymphocytes from the father who carried a balanced translocation t(11;18)(p15.4;p11.1). The breakpoint lay exactly in the same region. It could thus be inferred that the two sons, who were the first cases reported of BWS with dup11p15 and adrenocortical carcinoma (ADCC), carried a duplication similar to that observed in the first case. Together with evidence for specific somatic chromosomal events leading to loss of 11p15 alleles in familial cases of ADCC, it can be hypothesized that a gene involved in predisposition to ADCC maps to region 11p15.5.     

High frequency of copy number variations (CNVs) in the chromosome 11p15 region in patients with Beckwith–Wiedemann syndrome

Beckwith–Wiedemann syndrome (BWS), an overgrowth and tumor predisposition syndrome is clinically heterogeneous. Its variable presentation makes molecular diagnosis particularly important for appropriate counseling of patients with respect to embyronal tumor risk and recurrence risk. BWS is characterized by macrosomia, omphalocele, and macroglossia. Additional clinical features can include hemihyperplasia, embryonal tumors, umbilical hernia, and ear anomalies. BWS is etiologically heterogeneous arising from dysregulation of one or both of the chromosome 11p15.5 imprinting centers (IC) and/or imprinted growth regulatory genes on chromosome 11p15.5. Most BWS cases are sporadic and result from loss of maternal methylation at imprinting center 2 (IC2), gain of maternal methylation at imprinting center 1 (IC1) or paternal uniparental disomy (UPD). Heritable forms of BWS (15 %) have been attributed mainly to mutations in the growth suppressor gene CDKN1C, but have also infrequently been identified in patients with copy number variations (CNVs) in the chromosome 11p15.5 region. Four hundred and thirty-four unrelated BWS patients referred to the molecular diagnostic laboratory were tested by methylation-specific multiplex ligation-dependent probe amplification. Molecular alterations were detected in 167 patients, where 103 (62 %) showed loss of methylation at IC2, 23 (14 %) had gain of methylation at IC1, and 41 (25 %) showed changes at both ICs usually associated with paternal UPD. In each of the three groups, we identified patients in whom the abnormalities in the chromosome 11p15.5 region were due to CNVs. Surprisingly, 14 patients (9 %) demonstrated either deletions or duplications of the BWS critical region that were confirmed using comparative genomic hybridization array analysis. The majority of these CNVs were associated with a methylation change at IC1. Our results suggest that CNVs in the 11p15.5 region contribute significantly to the etiology of BWS. We highlight the importance of performing deletion/duplication testing in addition to methylation analysis in the molecular investigation of BWS to improve our understanding of the molecular basis of this disorder, and to provide accurate genetic counseling.     

Epigenetic alterations of H19 and LIT1 distinguish patients with Beckwith-Wiedemann syndrome with cancer and birth defects

Beckwith-Wiedemann syndrome (BWS) is a congenital cancer-predisposition syndrome associated with embryonal cancers, macroglossia, macrosomia, ear pits or ear creases, and midline abdominal-wall defects. The most common constitutional abnormalities in BWS are epigenetic, involving abnormal methylation of either H19 or LIT1, which encode untranslated RNAs on 11p15. We hypothesized that different epigenetic alterations would be associated with specific phenotypes in BWS. To test this hypothesis, we performed a case-cohort study, using the BWS Registry. The cohort consisted of 92 patients with BWS and molecular analysis of both H19 and LIT1, and these patients showed the same frequency of clinical phenotypes as those patients in the Registry from whom biological samples were not available. The frequency of altered DNA methylation of H19 in patients with cancer was significantly higher, 56% (9/16), than the frequency in patients without cancer, 17% (13/76; P=.002), and cancer was not associated with LIT1 alterations. Furthermore, the frequency of altered DNA methylation of LIT1 in patients with midline abdominal-wall defects and macrosomia was significantly higher, 65% (41/63) and 60% (46/77), respectively, than in patients without such defects, 34% (10/29) and 18% (2/11), respectively (P=.012 and P=.02, respectively). Additionally, paternal uniparental disomy (UPD) of 11p15 was associated with hemihypertrophy (P=.003), cancer (P=.03), and hypoglycemia (P=.05). These results define an epigenotype-phenotype relationship in BWS, in which aberrant methylation of H19 and LIT1 and UPD are strongly associated with cancer risk and specific birth defects.