Parental origin of de novo constitutional deletions of chromosomal band 11p13.

One-half of all cases of Wilms tumor (WT), a childhood kidney tumor, show loss of heterozygosity at chromosomal band 11p13 loci, suggesting that mutation of one allele and subsequent mutation or loss of the homologous allele are important events in the development of these tumors. The previously reported nonrandom loss of maternal alleles in these tumors implied that the primary mutation occurred on the paternally derived chromosome and that it was "unmasked" by loss of the normal maternal allele. This, in turn, suggests that the paternally derived allele is more mutable than the maternal one. To investigate whether germinal mutations are seen with equal frequency in maternally versus paternally inherited chromosomes, we determined the parental origin of the de novo germinal 11p13 deletions in eight children by typing lymphocyte DNA from these children and from their parents for 11p13 RFLPs. In seven of the eight cases, the de novo deletion was of paternal origin. The one case of maternal origin was unremarkable in terms of the size or extent of the 11p13 deletion, and the child did develop WT. Transmission of 11p13 deletions by both maternal and paternal carriers of balanced translocations has been reported, although maternal inheritance predominates. These data, in addition to the general preponderance of paternally derived, de novo mutations at other loci, suggest that the increased frequency of paternal deletions we observed is due to an increased germinal mutation rate in males.     

The E7-associated cell-surface antigen: a marker for the 11p13 chromosomal deletion associated with aniridia-Wilms tumor.

Unbalanced interstitial deletions of the p13 region of human chromosome 11 have been associated with congenital hypoplasia or aplasia of the iris, mental retardation, ambiguous genitalia, and predisposition to Wilms tumor of the kidney. Utilizing somatic cell hybrids containing either the normal or abnormal chromosome 11 from a child with Wilms tumor and aniridia, we previously mapped the E7 cell-surface antigen to the 11p1300-to-11p15.1 region. To localize even further the site of this antigen on chromosome arm 11p, we have produced somatic cell hybrids from the fibroblasts of a second child with Wilms tumor and aniridia and a different deletion of 11p [46,XY, del (11)(pter----p14.1::p11.2----qter)]. Furthermore, the normal and deleted chromosome 11 could also be distinguished on the basis of a restriction fragment length polymorphism for the beta-globin gene. Hybrid cells containing the deleted chromosome were not killed in the presence of complement and the E7 monoclonal antibody (which recognizes E7 cell surface antigen), while hybrid cells containing the patient's normal chromosome 11 were killed. Thus, expression of the E7-associated cell-surface antigen can be mapped to the 11p13 region, and it appears to be a potential marker of the chromosome abnormality associated with aniridia-Wilms tumor.     

A tumor chromosome rearrangement further defines the 11p13 Wilms tumor locus.

A sporadic Wilms tumor, WT-21, with an (11;14)-(p13;q23) reciprocal translocation has been identified. The translocation is found in tumor cells, but not in the patients' circulating lymphocytes. Molecular analysis of somatic cell hybrids segregating the derivative translocation chromosomes reveals a submicroscopic interstitial deletion at the translocation breakpoint, as well as a cytologically undetectable interstitial deletion in the nontranslocation chromosome 11, resulting in a homozygous deletion in 11p13. Pulsed-field gel analysis of tumor DNA indicates that the two deletions are indistinguishable, and the homozygously deleted region is less than 875 kb. The homozygously deleted regions of three other sporadic Wilms tumors overlap with the deleted region in WT-21, and the candidate cDNA clone for the 11p13 Wilms tumor gene described by Call et al. (Cell 60, 509-520, 1990) is included in the deleted region. These findings strengthen previous conclusions regarding the obligate location for the 11p13 WT locus and support the suggestion that the Wilms tumor gene has been cloned.     

Evidence for WT1 as a Wilms tumor (WT) gene: intragenic germinal deletion in bilateral WT.

The inactivation of two alleles at a locus on the short arm of chromosome 11 (band 11p13) has been suggested to be critical steps in the development of Wilms tumor (WT), a childhood kidney tumor. Two similar candidate WT cDNA clones (WT33 and LK15) have recently been identified on the basis of both their expression in fetal kidney and their location within the smallest region of overlap of somatic 11p13 deletions in some tumors. These homozygous deletions, however, are large and potentially affect more than one gene. Using a cDNA probe to the candidate gene, we have analyzed DNA from both normal and tumor tissue from WT patients, in an effort to detect rearrangements at this locus. We report here a patient with bilateral WT who is heterozygous for a small (less than 11 kb) germinal deletion within this candidate gene. DNA from both tumors is homozygous for this intragenic deletion allele, which, by RNA-PRC sequence analysis, is predicted to encode a protein truncated by 180 amino acids. These data support the identification of this locus as an 11p13 WT gene (WT1) and provide direct molecular data supporting the two-hit mutational model for WT.     

Definition of the limits of the Wilms tumor locus on human chromosome 11p13

In a previous report, we described a contiguous restriction map of chromosome band 11p13 that localized the Wilms tumor locus to a small group of NotI fragments. In an effort to identify and isolate the 11p13-associated sporadic Wilms tumor locus, we developed a panel of NotI fragment-specific DNA probes. These probes were selected from genomic libraries constructed using the Chinese hamster ovary-human somatic cell hybrid carrying only human 11p. The libraries were prepared from NotI-digested DNA after size selection by pulsed-field gel electrophoresis. The selected NotI fragments had been previously targeted on the basis of deletion mapping as having a high probability of containing the Wilms tumor locus. We used these newly identified 11p13-specific probes to improve the resolution of the restriction map spanning the Wilms tumor locus. The locus has been defined by a homozygous deletion in a sporadic Wilms tumor. Using these probes, the region of homozygous deletion in this tumor and presumably all or part of the Wilms tumor gene have been confined to two small SfiI fragments spanning less than 350 kb.     

Familial Wiedemann-Beckwith syndrome and a second Wilms tumor locus both map to 11p15.5.

Wilms tumor of the kidney occurs with increased frequency in association with two clinically and cytogenetically distinct congenital syndromes, the Wiedemann-Beckwith syndrome (WBS) and the triad of aniridia, genitourinary anomalies, and mental retardation (WAGR). Constitutional deletions in the latter situation and similar alterations in sporadic Wilms tumors have implicated the chromosomal 11p13 region in neoplastic development. In contrast, some sporadic cases of WBS have been reported to have a constitutional duplication of chromosome 11p15. In order to resolve this seeming paradox, we have analyzed a family segregating WBS for linkage to DNA markers mapped to chromosome 11p. Consonant with the cytogenetic alterations in sporadic WBS cases, we obtained evidence for tight linkage of the mutation causing the syndrome to markers located at 11p15.5. Also consistent with this localization, we identified a subset of Wilms tumors, not associated with WBS, which have attained somatic homozygosity through mitotic recombination, with the smallest shared region of overlap being distal to the beta-globin complex at 11p15.5. These data provide evidence that familial WBS likely results from a defect at the same genetic locus as does its sporadic counterpart. Further, the data suggest there is another locus, distinct from that involved in the WAGR syndrome, which plays a role in the association of Wilms tumor with WBS.     

High-resolution studies in patients with aniridia-Wilms tumor association,Wilms tumor or related congenital abnormalities

Summary We attempted to determine wheter all cases of AWTA (anirida-Wilms tumor association) or any of the following groups of patients show 11p deletion: cases of Wilms tumor with congenital abnormalities other than aniridia, those without any congenital abnormalities, tumor itself in cases of Wilsm tumor without constitutional 11p deletion and cases of aniridia or hemihypertrophy without Wilms tumor. We studied a total of 29 index patients including five cases of AWTA, four cases of Wilms tumor with various congenital abnormalities, 16 cases of Wilms tumor without other abnormalities, three cases of aniridia in one of which Wilms tumor developed later and a case of hemihypertrophy.In all five cases of AWTA and in a case of aniridia who later developed Wilms tumor, 11p deletion involving the p13 band was detected. The mother of the latter also showed an identical 11p deletion. The common segment of deletion was the middle part of the p13. Two possible hypotheses on the mechanism through which Wilms tumor might develop were evaluated, based on the distribution of break points. All other cases, including five with tumor culture, showed a normal karyotype.     

Loss of alleles at loci on chromosome 13 in human primary gastric cancers

Mitotic events leading to the loss of the normal allele corresponding to a mutated gene are important for tumorigenesis in rare heritable tumors such as retinoblastoma and Wilms tumor. As reported for both colorectal and breast cancers, some common tumors seem to develop because of the same mitotic events. We examined constitutional and tumor genotypes defined by polymorphic DNA clones in 36 patients with gastric cancer. In 14 cases, constitutional heterozygosity at loci on chromosome 13 had been lost. Loss of alleles was also detected at a locus on chromosome 18 in two cases and at a locus on chromosome 17 in one case. The frequent loss of alleles at loci on chromosome 13 (41%) suggests that elimination of genes on this chromosome may be of importance in the tumorigenesis of human primary gastric cancers.     

Coding mutations in p57KIP2 are present in some cases of Beckwith-Wiedemann syndrome but are rare or absent in Wilms tumors.

The Beckwith-Wiedemann syndrome (BWS) is marked by fetal organ overgrowth and conveys a predisposition to certain childhood tumors, including Wilms tumor (WT). The genetics of BWS have implicated a gene that maps to chromosome 11p15 and is paternally imprinted, and the gene encoding the cyclin-cdk inhibitor p57KIP2 has been a strong candidate. By complete sequencing of the coding exons and intron/exon junctions, we found a maternally transmitted coding mutation in the cdk-inhibitor domain of the KIP2 gene in one of five cases of BWS. The BWS mutation was an in-frame three-amino-acid deletion that significantly reduced but did not fully abrogate growth-suppressive activity in a transfection assay. In contrast, no somatic coding mutations in KIP2 were found in a set of 12 primary WTs enriched for cases that expressed KIP2 mRNA, including cases with and without 11p15.5 loss of heterozygosity. Two other 11p15.5 loci, the linked and oppositely imprinted H19 and IGF2 genes, have been previously implicated in WT pathogenesis, and several of the tumors with persistent KIP2 mRNA expression and absence of KIP2 coding mutations showed full inactivation of H19. These data suggest that KIP2 is a BWS gene but that it is not uniquely equivalent to the 11p15.5 "WT2" tumor-suppressor locus.     

A common region of loss of heterozygosity in Wilms' tumor and embryonal rhabdomyosarcoma distal to the D11S988 locus on chromosome 11p15.5

The development of Wilms' tumor has been associated with two genetic loci on chromosome 11: WTI in 11p13 and WT2 in 11p15.5. Here, we have used loss of heterozygosity (LOH) in Wilms' tumors to narrow the WT2 locus distal to the D11S988 locus. A similar region was apparent for the clinically associated tumor, embryonal rhabdomyosarcoma. We have also demonstrated that a constitutional chromosome translocation breakpoint associated with Beckwith-Wiedemann syndrome and an acquired somatic chromosome translocation breakpoint in a rhabdoid tumor each occur in the same chromosomal interval as the smallest region of LOH in Wilms' tumors and embryonal rhabdomyosarcoma. Finally, we report the first Wilms' tumor without a cytogenetic deletion that shows targeted LOH for 11p15 and 11p13 while maintaining germline status for 11p14.     

Sequences which flank an 11p deletion observed in an hepatocellular carcinoma map to 11p13

Summary There is considerable interest in the 11p13 region because of its involvement in Wilms tumor, sporadic aniridia, and other congenital abnormalities. Cloned DNA sequences from this region might be useful in understanding the chromosomal abnormalities which lead to such disorders. However, few such markers exist. Using somatic cell hybrids which contain defined 11p deletions, two cloned DNA sequences which flank a deletion generated in an hepatocellular carcinoma (as a consequence of hepatitis B virus integration) were mapped to 11p13. Thus both ends of the deletion observed in an hepatocellular carcinoma are within 11p13.     

The distal region of 11p13 and associated genetic diseases.

The distal region of human chromosome band 11p13 is believed to contain a cluster of genes involved in the development of the eye, kidney, urogenital tract, and possibly the nervous system. Genetic abnormalities of this region can lead to Wilms tumor, aniridia, urogenital abnormalities, and mental retardation (WAGR syndrome). Using 11 DNA markers covering the entire distal region of 11p13, including the WAGR region, we have carried out molecular studies on 58 patients with one or more features of this syndrome and patients with other diseases or structural cytogenetic abnormalities associated with 11p13. Cytogenetic analyses were performed in all cases. In 12 patients we were able to demonstrate deletions of this region. In 2 patients balanced translocations and in 2 additional patients duplications of this region were characterized. In total, 5 chromosomal breakpoints within 11p13 were identified. One of these breakpoints maps within the smallest region of overlap of WAGR deletions. Moreover, we were unable to demonstrate constitutional deletions in a candidate sequence for the Wilms tumor gene or any other marker in 2 patients with aniridia and urogenital abnormalities, 4 patients with Wilms tumor and urogenital abnormalities, 5 patients with bilateral Wilms tumors, and 3 familial Wilms tumor cases. We suggest that the molecular techniques used here (heterozygosity testing for polymorphic markers mapping between AN2 and WT1 and deletion analysis by dosage, cytogenetic analysis, or in situ hybridization) can be employed to identify sporadic aniridia patients with and without increased tumor risk.     

Use of catalase polymorphisms in the study of sporadic aniridia

Summary Catalase is known to map at chromosome 11p13. It is one of the closest known markers to the WAGR locus. Restriction fragment length polymorphisms (RFLP) of the catalase gene may be invaluable for studying rearrangements in somatic tumours, linkage in cases of familial Wilms tumour, and the relationship between sporadic and familial aniridia. We describe a catalase RFLP with two different enzymes and use these polymorphisms to exclude deletion of the catalase gene in patients with sporadic aniridia, including one who is known to have a deletion and another suspected of having a deletion.     

Mitotic deletions of 11p15.5 in two different tumors indicate that the CALCA locus is distal to the PTH locus

We have compared the constitutional and tumor genotypes in two patients with Wilms tumor and adrenocortical carcinoma. The allelic distribution of chromosome 11-specific markers spanning chromosome 11 from pter to qter (HRAS1-HBB-[CALCA/PTH]-FSHB-CAT-APOA1) and an approach combining RFLP analysis and gene copy number determination showed that a mitotic deletion had occurred in both tumors. The loss of one copy of the gene for alpha-calcitonin-gene-related polypeptide (CALCA), together with that of a more distal marker (HRAS1 or HBB), indicates that CALCA is distal to the gene for parathyroid hormone (PTH), which was not deleted in either tumor. These results suggest that mitotic deletion mapping may be as useful as meiotic deletion or recombination mapping in ordering closely linked markers, such as CALCA and PTH, for which other approaches, including physical mapping and multipoint linkage analysis, have failed to accurately identify the gene order.     

Loss of allelic heterozygosity at a second locus on chromosome 11 in sporadic Wilms'' tumor cells.

Children with associated Wilms' tumor, aniridia, genitourinary malformations, and mental retardation (WAGR syndrome) frequently have a cytogenetically visible germ line deletion of chromosomal band 11p13. In accordance with the Knudson hypothesis of two-hit carcinogenesis, the absence of this chromosomal band suggests that loss of both alleles of a gene at 11p13 causes Wilms' tumor. Consistent with this model, chromosomes from sporadically occurring Wilms' tumor cells frequently show loss of allelic heterozygosity at polymorphic 11p15 loci, and therefore it has been assumed that allelic loss extends proximally to include 11p13. We report here that in samples from five sporadic Wilms' tumors, allelic loss occurred distal to the WAGR locus on 11p13. In cells from one tumor, mitotic recombination occurred distal to the gamma-globin gene on 11p15.5. Thus, allelic loss in sporadic Wilms' tumor cells may involve a second locus on 11p.     

Delineation and physical separation of novel translocation breakpoints on chromosome 1p in two genetically closely associated childhood tumors

Sporadic childhood tumors associated with Beckwith-Wiedemann syndrome (BWS) all show abnormalities of the same region on chromosome 11. In addition to chromosome 11, other chromosome regions are affected in some of these tumor types. In this study we analyzed the region on chromosome 1p involved in the etiology of BWS-associated tumors, Wilms tumor, rhabdomyosarcoma, and hepatoblastoma. For this purpose we determined the location of two novel translocation breakpoints in this chromosome region in cells from a Wilms tumor and cells from a rhabdomyosarcoma. We constructed a map of the region and found that both breakpoints are separated by at least 875 kb. We identified a PAC clone which crosses the rhabdomyosarcoma breakpoint and found several exons within this clone. We established that this breakpoint is located proximal to the PAX7 gene and, therefore, identified a new region involved in the etiology of rhabdomyosarcomas.     

Constitutional and somatic deletions of two different regions of maternal chromosome 11 in Wilms tumor

Loss of heterozygosity for 11p markers and preferential loss of maternal alleles have been described in Wilms tumor. In this report we describe the molecular characterization of the constitutional and somatic 11p rearrangements in a del(11p13) WAGR patient with Wilms tumor. Both rearrangements led to loss of maternal alleles for two different regions of 11p, namely, 11p13 and 11p14----p15. This result clearly suggests that Knudson's hypothesis of two hits at the same locus does not necessarily apply to Wilms tumor. Moreover, the loss of 11p15 maternal alleles in the tumor is not incompatible with maternal inheritance of predisposition at 11p13. The putative roles of these two loci are discussed.     

Smallest region of overlap in Wilms tumor deletions uniquely implicates an 11p13 zinc finger gene as the disease locus.

The development of Wilms tumor (WT) has been associated with the inactivation of a "tumor suppressor" locus in human chromosome 11 band p13. Several WTs that exhibit homozygous deletions of an 11p13 candidate WT gene in its entirety have been reported. We report here a partial deletion of the candidate gene which, upon comparison with other documented homozygous deletions, permitted a precise definition of the critical genomic target in Wilms tumor. The smallest region of overlap between these deletions is a 16-kb segment of DNA encompassing the 5' exon(s) of an 11p13 gene coding for a zinc finger protein, together with an associated CpG island. This finding supports the notion that the candidate gene in question corresponds to the 11p13 WT1 Wilms tumor locus.     

The gene for catalase is assigned between the antigen loci MIC4 and MIC11

Genetic analysis of the cells of a WAGR patient (W, predisposition to Wilms tumor; A, aniridia; G, genitourinary abnormalities; R, mental retardation), bearing a partial deletion of band 11p13, was performed with biochemical and antigenic 11p markers by using gene dosage, somatic hybridization, molecular hybridization, and indirect immunofluorescence techniques. These studies allowed the regional assignment of the gene for catalase, which is linked to the Wilms tumor locus, between MIC4 and MIC11, two loci encoding for membrane antigens previously mapped to band 11p13.