Aniridia, cataracts, and Wilms' tumor in monozygous twins

Three patients with hallucal polydactyly and WAGR syndrome, including discordant expression of Wilms tumor in MZ twins

The WAGR contiguous gene deletion syndrome is a combination of Wilms tumor, Aniridia, Genito-urinary abnormalities, and growth and mental retardation which is invariably associated with an 11p13 deletion. We report two monozygotic twins and a third, unrelated patient with WAGR syndrome and additional clinical features not usually associated with WAGR. Both twins had developmental delay, growth deficiency, severe ocular involvement (nystagmus, aniridia, cataracts), atrial septal defect and two uncommon findings: agenesis of the corpus callosum and duplication of the halluces. One twin developed Wilms tumors aged 19 months while her sister remained tumor free by the age of 6.5 years. The singleton patient showed typical WAGR syndrome and preaxial hallucal polydactyly. Molecular cytogenetic studies refined the identification of the extent of the deleted segments, which were not identical in the two families. The two deletions included the PAX6 and WT1 genes as previously reported in typical WAGR patients. The unusual anomalies described in this report, may represent the expression of low penetrant traits associated with haploinsufficency of one or more of the genes present in the deletion (PAX6 is expressed in CNS) or may indicate epistatic influences of modifier genes on the expression of gene(s) present in the WAGR region.

Partial duplication 4q and deletion 1p36 in monozygotic twins with discordant phenotypes

We report on monozygotic (MZ) twins with a de novo chromosome abnormality consisting of a partial duplication of chromosome 4 (q25-qter) and deletion of chromosome 1p36. These infants had dysmorphic facial features and other clinical manifestations similar to those described with the previously delineated duplication 4q and deletion 1p36 phenotypes and two other reported cases of combined partial duplication 4q and deletion 1p36. However, the twins were discordant for a number of congenital anomalies. The discordant phenotypes described in these genetically identical infants demonstrate that nongenetic factors may play a significant role in the phenotypic differences in patients with recognized chromosome duplication and deletion syndromes, which are usually attributed to the individual genotypic differences in the duplicated and/or deleted chromosome segments.

Effects of PAX6 mutations on retinal function: an electroretinographic study

PURPOSE

To investigate the retinal function in aniridic patients with documented PAX6 mutations to determine the range of electroretinogram abnormalities in aniridic patients and to relate electroretinogram findings with specific PAX6 mutations.

METHODS

Eleven patients with typical aniridia and fully characterized PAX6 mutations underwent electroretinography.

RESULTS

In all 11 patients, electroretinogram recordings were abnormal, ranging from mild to severe. Rod-related and cone-related activities were equally affected. The amplitude of the oscillatory potentials was the most reduced, followed by the b-wave, then to a milder degree the a-wave. Mutations affecting the paired domain of the PAX6 protein had the biggest impact on the electroretinogram amplitudes. Implicit times were increased in a subgroup with mutations affecting only the homeodomain.

CONCLUSION

Patients with aniridia have varying degree of retinal dysfunction, ranging from severely abnormal to almost normal. The paired domain appears to have more impact on retinal function than other regions of the PAX6 protein. It is unclear whether mutations affecting the homeodomain lead to alteration of the photoreceptor function.

The importance of DNA analysis in sporadic aniridia

Total aniridia was found in a 2-month-old baby boy. Otherwise the baby was healthy. Ophthalmological examination of the elder sister, parents and paternal grandparents revealed no abnormalities. There was no consanguinity between the parents. Hence, the aniridia was considered sporadic, and the possibility of Wilms' tumour had to be taken into consideration. The chromosomes of the baby were normal, as judged by conventional cytogenetic analysis. In addition, DNA analysis demonstrated that there was no subchromosomal deletion in band 11p13, spanning the aniridia-Wilms' tumour region. Therefore, we conclude that the genetic defect leading to aniridia is confined to the aniridia locus and that the child has no increased risk of developing Wilms' tumour.

Cancer in twins of Wilms tumor patients

We interviewed families of 71 patients registered in the National Wilms Tumor Study and identified as having a twin sibling. Questions concerning zygosity and the occurrence of congenital anomalies and other forms of cancer in the twins were asked. Of the 71 twin pairs, 35 were dizygotic, 31 were monozygotic, and 5 were of unknown zygosity. The only pair concordant for Wilms tumor was dizygotic, leading to a heritability estimate of zero. In a monozygotic pair, one twin was diagnosed with Wilms tumor and the other with medulloblastoma. The estimated relative risk of Wilms tumor and childhood cancer in the co-twin was 250 times and 10 times the population rate, respectively. Four discordant pairs had a family history of Wilms tumor, suggesting that the penetrance of the condition is not complete. Because of the small sample size, caution should be exercised in the interpretation of these results.

Results of penetrating keratoplasty in aniridia

Eight aniridic patients with bilateral corneal scarring, vascularization, or edema underwent corneal transplantation in one or both eyes (11 eyes). Follow-up ranged from eight months to 5 1/2 years (average, three years). Six of 11 eyes (55%) had at least a two-line improvement in visual acuity and eight of 11 (73%) had at least one line of improvement. Best-corrected visual acuity was 20/200 or worse in nine of 11 eyes (82%), however. Postoperative complications included whorl keratopathy, persistent epithelial defects, central subepithelial scarring, peripheral vascularization with pannus, and graft rejection. Glaucoma was well controlled medically but five of nine patients (56%) with preexisting glaucoma needed an increase in medication for intraocular pressure control. Graft rejection occurred in seven of 11 eyes (64%) and three of these eyes required repeat transplantation.

Genetics and epidemiology of Wilms' tumor: the French Wilms' tumor study

A complete family history was obtained for 501 patients with Wilms' tumor, treated in departments of pediatric oncology in whole France. The information was collected by self-questionnaire and/or by interview of parents. The proportion of bilateral cases is 4.6% and there are 12 patients (2.4%) with a positive family history of Wilms' tumor. The affected relatives are most often distant and no first degree relative was affected. Apart from the well-known associations with aniridia, hemihypertrophy, genitourinary anomalies, Beckwith-Wiedeemann, and Drash syndromes, there is also a significant excess of congenital heart defects (P = .008) which remains to be explained. Several findings support the bimutational hypothesis such as earlier diagnosis and increased parental age in bilateral cases. No particular anomalies and no increased frequency of childhood cancer were found in patients' relatives. The frequency of Wilms' tumor in relatives was estimated to be less than 0.4% in sibs, 0.06% in uncles and aunts, and 0.04% in first cousins. These figures are very different from those found in retinoblastoma and suggest that the mechanism may be more complex in Wilms' tumor. This conclusion is in agreement with molecular biology studies in tumors and linkage analysis in multiple case families which suggest that more than one locus is involved.

Aniridia, Wilms' tumor and human chromosome 11

Aniridia-a developmental abnormality of the eye in which the iris is apparently absent-has been shown to be genetically associated with Wilms' tumor (an embryonic nephroblastoma) in the WAGR syndrome. Genetic and cytogenetic evidence points to band p13 of human chromosome 11 as the localization of the genes responsible for these defects. Deleted chromosomes 11 from WAGR patients and clinically associated translocations involving 11p13 have been used to map and order genes and anonymous DNA markers around the WAGR locus refining the localization of the aniridia and Wilms' tumor genes to within about 1 million base pairs of DNA.

CpG islands surround a DNA segment located between translocation breakpoints associated with genitourinary dysplasia and aniridia

We have isolated a DNA segment absent from all the constitutionally deleted chromosomes 11 of our patients with Wilms tumor. This marker separates two balanced translocations that break in band 11p13: the distal one associated with aniridia (AN2), and the proximal one with genitourinary dysplasia (GUD). The GUD breakpoint maps within the smallest region of overlap (SRO) for the Wilms tumor (WT) gene locus, thus strengthening the previous suggestion of an association between Wilms tumor and other abnormalities of the genitourinary system. The 11p13 translocation breakpoint associated with T-cell acute lymphatic leukemia (T-ALL) is centromeric to the SRO and separated from the WT locus by at least one known gene. This region of the human genome (11p13) is rich in CpG islands that potentially identify genes, some of which may be involved in the various phenotypes associated with the WAGR syndrome. This is consistent with the proposition that the majority of human genes are in G-negative bands.

Sporadic aniridia and Wilms' tumor: visual function evaluation of three cases

The visual function of three infants with sporadic aniridia associated with Wilms' tumor and a deletion of the short arm of chromosome 11 was evaluated with electrophysiological tests. The patients presented nystagmus and photophobia. The electroretinograms (ERGs) were normal, as in other sporadic cases, but at variance with the familial cases. The latency of the flash visual evoked potentials (FVEPs) became shorter with time but remained longer than in age-matched controls, suggesting a delay in maturation of the nervous system. Poor visual function in our cases did not appear to be the result of gross retinal anomalies, as shown by the normal ERG, nor of an hypoplasia of the optic nerve. Contact lenses that provide an artificial pupil decreased photophobia and nystagmus and are therefore highly recommended to increase patient comfort.

Homozygous deletion of a DNA marker from chromosome 11p13 in sporadic Wilms tumor

A random DNA fragment, probe p2.3 (locus D11S87), was cloned from the 11p13 region between a translocation breakpoint associated with familial aniridia and another translocation breakpoint associated with childhood T-cell leukemia. The D11S87 locus maps between the catalase (CAT) locus and the beta subunit of follicle stimulating hormone (FSHB). The D11S87 locus is deleted in a Wilms tumor patient with a constitutional deletion of 11p and in a case of sporadic Wilms tumor (WiT-13) apparently with normal karyotype. In the WiT-13 tumor both maternal and paternal chromosomes 11 are retained; D11S87 is deleted homozygously and FSHB hemizygously. These results suggest two mutational events resulting in homozygous deletion in this patient. The D11S87 homozygous deletion was also demonstrated in WiT-13 nude mouse heterotransplants and in fibroblast-like cell line derived from the primary tumor. The minimum size of the deletion was estimated to be 30 kb as determined by cosmid screening and hybridization. As homozygous deletions in the 11p13 region have not been previously reported for sporadic Wilms tumors, these findings place the D11S87 locus within or approximate to the Wilms tumor gene.

Microdeletion syndromes, balanced translocations, and gene mapping

High resolution prometaphase chromosome banding has allowed the detection of discrete chromosome aberrations which escaped earlier metaphase examinations. Consistent tiny deletions have been detected in some well established malformation syndromes: an interstitial deletion in 15q11/12 in the majority of patients with the Prader-Willi syndrome and in a minority of patients with the Angelman (happy puppet) syndrome; a terminal deletion of 17p13.3 in most patients examined with the Miller-Dieker syndrome; an interstitial deletion of 8q23.3/24.1 in a large majority of patients with the Giedion-Langer syndrome; an interstitial deletion of 11p13 in virtually all patients with the WAGR (Wilms' tumour-aniridia-gonadoblastoma-retardation) syndrome; and an interstitial deletion in 22q11 in about one third of patients with the DiGeorge sequence. In addition, a combination of chromosome prometaphase banding and DNA marker studies has allowed the localisation of the genes for retinoblastoma and for Wilms' tumour and the clarification of both the autosomal recessive nature of the mutation and the possible somatic mutations by which the normal allele can be lost in retina and kidney cells. After a number of X linked genes had been mapped, discrete deletions in the X chromosome were detected by prometaphase banding with specific attention paid to the sites of the gene(s) in males who had from one to up to four different X linked disorders plus mental retardation. Furthermore, the detection of balanced translocations in probands with disorders caused by autosomal dominant or X linked genes has allowed a better insight into the localisation of these genes. In some females with X linked disorders, balanced X; autosomal translocations have allowed the localisation of X linked genes at the breakpoint on the X chromosome. Balanced autosome; autosome translocations segregating with autosomal dominant conditions have provided some clues to the gene location of these conditions. In two conditions, Greig cephalopolysyndactyly and dominant aniridia, two translocation families with one common breakpoint have allowed quite a confident location of the genes at the common breakpoint at 7p13 and 11p13, respectively.

Simultaneous cloacogenic carcinoma in dizygotic twins

Dizygotic twins developed cloacogenic carcinoma of the anus almost simultaneously. The patients, although separated from the time they were 20-years-old, had very similar life styles. There are several reports in the medical literature of synchronous tumors in mono and dizygotic twins. It is recommended that if a cancer diagnosis is made in one twin, the other undergo workup to exclude the presence of a tumor with similar histology. The establishment of state or national twin registries would provide valuable information regarding the role of genetic and environmental factors in the development of not only cancer but also of various nonmalignant disorders.

Male pseudohermaphroditism, partial androgen receptors defect, 11p13 deletion: indication of gene localization

A partial androgen receptor defect was found in a boy with male pseudohermaphroditism and an 11p13 deletion. We hypothesize that a gene responsible for the function or structure of androgen receptors might be localized in the 11p13 band or in close proximity to it.

The beta-subunit of follicle-stimulating hormone is deleted in patients with aniridia and Wilms' tumour, allowing a further definition of the WAGR locus

One in 10,000 children develops Wilms' tumour, an embryonal malignancy of the kidney. Although most Wilms' tumours are sporadic, a genetic predisposition is associated with aniridia, genito-urinary malformations and mental retardation (the WAGR syndrome). Patients with this syndrome typically exhibit constitutional deletions involving band p13 of one chromosome 11 homologue. It is likely that these deletions overlap a cluster of separate but closely linked genes that control the development of the kidney, iris and urogenital tract (the WAGR complex). A discrete aniridia locus, in particular, has been defined within this chromosomal segment by a reciprocal translocation, transmitted through three generations, which interrupts 11p13. In addition, the specific loss of chromosome 11p alleles in sporadic Wilms' tumours has been demonstrated, suggesting that the WAGR complex includes a recessive oncogene, analogous to the retinoblastoma locus on chromosome 13. In WAGR patients, the inherited 11p deletion is thought to represent the first of two events required for the initiation of a Wilms' tumour, as suggested by Knudson from epidemiological data. We have now isolated the deleted chromosomes 11 from four WAGR patients in hamster-human somatic cell hybrids, and have tested genomic DNA from the hybrids with chromosome 11-specific probes. We show that 4 of 31 markers are deleted in at least one patient, but that of these markers, only the gene encoding the beta-subunit of follicle-stimulating hormone (FSHB) is deleted in all four patients. Our results demonstrate close physical linkage between FSHB and the WAGR locus, suggest a gene order for the four deleted markers and exclude other markers tested from this region. In hybrids prepared from a balanced translocation carrier with familial aniridia, the four markers segregate into proximal and distal groups. The translocation breakpoint, which identifies the position of the aniridia gene on 11p, is immediately proximal to FSHB, in the interval between FSHB and the catalase gene.

Familial isolated aniridia associated with a translocation involving chromosomes 11 and 22 [t(11;22)(p13;q12.2)]

Isolated aniridia segregated as an autosomal dominant trait in a family with 11 affected members spanning five generations. Four of the eight individuals studied had aniridia associated with glaucoma and cataracts. Cytogenetic studies revealed an apparently balanced reciprocal translocation between chromosomes 11 and 22 [t(11;22)(p13;q12.2)], while four unaffected relatives had normal karyotypes. There is no evidence of Wilms tumor or genitourinary abnormalities in any members of the family. Restriction enzyme analysis of the human catalase gene revealed no abnormalities in the individuals with the translocation. A summary of phenotypic abnormalities in 61 cases associated with aniridia is presented, as well as a comparison of breakpoints in 44 cases of 11p deletion. These data indicate that single breaks at 11p13 are associated with isolated aniridia, while deletion of 11p13 results in aniridia combined with Wilms tumor, genitourinary abnormalities, and/or mental retardation.

Molecular analysis of chromosome 11 deletions in aniridia-Wilms tumor syndrome

We describe five individuals who have constitutional deletions of the short arm of one chromosome 11, including all or part of the band p13. All of these individuals suffer from aniridia; two have had a Wilms tumor removed. We have established lymphoblastoid cell lines from these and in three cases constructed somatic cell hybrids containing the deleted chromosome 11. Analysis of DNA from the cell lines and hybrids with a cloned cDNA probe has shown that the catalase gene is deleted in four of five patients. The catalase locus must be proximal to the Wilms and aniridia-related loci. We have not detected a deletion of the beta-globin or calcitonin genes in any of these individuals; we conclude these genes are likely to be outside the region 11p12-11p15.4. In addition, we have used monoclonal antibodies in fluorescence-activated cell sorting analysis to measure expression in the hybrids of two cell surface markers encoded by genes that map to the short arm of chromosome 11. The genes for both of these are deleted in two individuals but are present in the individual with the smallest deletion.

A complex rearrangement, including a deleted 8q, in a case of Langer-Giedion syndrome

A 10-month-old infant with failure to thrive, delayed development, mild dysmorphia, cardiac anomalies, and cryptorchidism was referred for cytogenetic evaluation. Routine GTG-banded analysis revealed a modal number of 46 chromosomes, which contained an obvious complex rearrangement involving chromosomes 1, 8, and 14. Parental chromosomes were normal. Following high resolution techniques, this de novo rearrangement demonstrated an intraband deletion and was designated as [46,XY,t(1;8;14)(1pter----1p13.1::14q12----14pter++ +;1qter----1p13.1::8q24.13----8qter; 14qter----14q12::8p23.3----8q24.11:)]. Although deletions have been implicated as possibly responsible for abnormal phenotypes in patients with de novo "balanced rearrangements", in most cases, they could not be demonstrated. The present case is only the second instance documenting a subtle intraband deletion in association with a complex translocation. Fourteen of the reported 18 patients with an 8q deletion (including this infant) have Langer-Giedion syndrome, suggesting an etiologic relationship. However, the same deletion is not present in all cases.

Del 11p/aniridia complex. Report of three patients and review of 37 observations from the literature

Three patients (two females, one male) are reported with bilateral aniridia, Wilms' tumor, more or less moderate mental retardation, decreased catalase activity, and del 11p13. These and 34 case reports from the literature are discussed with respect to: sex ratio, maternal age, type of chromosomal imbalance and frequency of associated rearrangements, prevalence of aniridia and other eye disorders, predisposition to tumor development, genitourinary anomalies, growth and mental retardation, and catalase involvement. Possible gene relationship within the complex locus and with neighbouring 11p genes is discussed.

Aniridia. A review

Aniridia occurs as a phenotypically heterogeneous condition which may be inherited as an autosomal dominant disorder or as part of several systemic syndromes. It has been linked with the loci of chromosomes 1 and 2 and associated with the deletion of the p-13 band of chromosome 11. Aniridia may occur in a highly penetrant form in association with other ocular abnormalities with poor vision or in a more variable form with good vision. The recognition of a child with sporadic aniridia should alert physicians to the increased risk of development of Wilms' tumor.

Catalase determination in various etiologic forms of Wilms' tumor and gonadoblastoma

We have previously mapped the gene coding for catalase to 11p13 by gene dosage analysis. Deletion of this chromosomal region causes aniridia, mental retardation, and predisposition to Wilms' tumor (WT). In the present study, 22 patients with various etiologic forms of WT and/or aniridia were investigated. The catalase (CAT) level and karyotype were examined in order to determine the linkage and the gene ordering on chromosome number 11 of the different loci involved. The CAT concentration was normal in the 19 cases without detectable chromosomal abnormalities.

Wilms's tumour and aniridia: clinical and cytogenetic features

A survey carried out to detect children with aniridia/Wilms's tumour syndrome identified 8 living and 3 dead children. The incidence of aniridia was found to be 1 in 43 among Wilms's tumour patients in the UK. The clinical features included complete bilaterial aniridia, cataracts, glaucoma, mental retardation, hyperkinesis, hypospadias, and undescended testes. A high incidence of bilateral tumours (36%), male sex, presentation at a young age, and advanced maternal age appeared to be associated with the syndrome. The 8 living children each had a deletion on the short arm of chromosome 11. In contrast, although 2 patients with sporadic aniridia without Wilms's tumour had other malformations, neither had genitourinary anomalies, and the only additional problems in patients with familial aniridia were cataracts. Among 49 children with Wilms's tumour without aniridia ony one had bilateral tumours. No chromosome abnormalities were detected in patients with familial aniridia, nor were they detected in patients with Wilms's tumour without aniridia or in those with sporadic aniridia without Wilms's tumour. While many infants with the Wilms's tumour/aniridia syndrome are clinically diagnosable at birth, chromosome analysis using the elongated chromosome method is especially valuable to confirm the diagnosis in girls with sporadic aniridia and in boys who lack the genitourinary malformations. The presence of an 11p13 deletion confirms the diagnosis of the Wilms's tumour/aniridia syndrome and indicates a very high risk for the development of Wilms's tumour.

Association of del(11)(p15.1p12), aniridia, catalase deficiency, and cardiomyopathy

We report another patient with del(11p) and aniridia, catalase deficiency, and cardiomyopathy. This association is confirmed from a review of previously reported cases. Since other dysplasias are known in this syndrome, the hypertrophic cardiomyopathy in del(11p) children may also represent an abnormality of tissue development.

Aniridia caused by a heritable chromosome 11 deletion

A child with aniridia, multiple anomalies, severe failure to thrive, and severe psychomotor retardation is shown to have a syndrome similar to, though more severe than, other patients with overlapping deletions of the short arm of chromosome 11 (Pediatrics 64:604, 1978). Her deletion (46,XX,del [11p] [pter yields p14::p11.3 yields qter]) was derived from her mother, who has a chromosome 11 shift (46,XX,der [11] [pter yields p14::p11.3 yields q22::p14 yields p11.3::q22 yields qter]). The significance of del (11p) in the aniridia-Wilms' tumor association is discussed, and the del (11p) basis for aniridia is compared with other genetic bases for aniridia.