Genetic counseling in retinoblastoma.
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Eye Neoplasms↗
Biomedical subjects
J K Cowell
Publications and source records attributed to J K Cowell.
Application of PCR amplification of DNA from paraffin embedded tissue sections to linkage analysis in familial retinoblastoma.
A family segregating for the retinoblastoma predisposition gene has been analysed using the polymerase chain reaction to exclude their son as being an affected gene carrier. The unusual feature of this family is that the affected child, who would ordinarily have been used to establish phase in a linkage study, died as a result of developing a second tumour some years ago. The only tissue available from this child was a paraffin embedded, formalin fixed histopathological specimen from the second tumour. It was possible to isolate DNA from this tissue and amplify the DNA flanking two polymorphic restriction enzyme sites to establish alleles which cosegregated with tumour predisposition. Archival material can now be used to offer families such as this prenatal screening to provide informed genetic counselling.
Base Sequence↗
Isolation and regional localization of 25 anonymous DNA probes on a chromosome 13 hybrid panel.
Clones were isolated from two flow-sorted chromosome 13 libraries. Twenty-five clones were localized to various regions of chromosome 13, using a well-characterized panel of rodent x human hybrid cell lines. Eight DNA markers were localized to 13q14.2----q22, where the gene for Wilson disease, a recessive disorder of copper metabolism, was previously assigned. The new markers will be useful for the diagnosis of presymptomatic sibs of Wilson disease patients. We isolated six DNA clones proximal to the retinoblastoma gene, a region in which a translocation associated with rhabdomyosarcoma has been observed. Probes for both of these regions will be useful for the cloning of the genes involved in these diseases.
Animals↗
Structural rearrangements of the WT1 gene in Wilms' tumour cells.
We have analysed 55 Wilms' tumour DNAs using the cDNA from the candidate Wilms' predisposition gene, WT1. One tumour, GOS 129, shows a partial homozygous deletion involving only the 3'-most exon of the gene. An adjacent 3' DNA sequence, J7-18, which lies on the same NotI fragment as WT1, is present in GOS 129. Thus, this partial deletion does not extend to the adjacent unmethylated 3' HTF island. These data support the candidature of WT1 as a Wilms' predisposition gene. Tumour GOS 129 has become homozygous as a result of a mitotic recombination event proximal to WT1. Three other tumours showed abnormally sized bands on Southern blot analysis which appear to reflect internal heterozygous rearrangements involving the 5' end of the gene. One of these tumours was from a bilaterally-affected patient and the other 3 were from stage III or IV tumours.
Blotting, Southern↗
Molecular definition in a somatic cell hybrid of a specific 2:13 translocation breakpoint in childhood rhabdomyosarcoma.
A consistent, balanced, reciprocal chromosomal translocation t(2:13) (q35:q14) has been identified in alveolar rhabdomyosarcoma. Somatic cell hybrids have been constructed between rhabdomyosarcoma cell lines carrying the (2:13) translocation and mouse 3T3 cells. One hybrid cell line was shown to have retained the derivative (13:2) chromosome, but segregated the normal chromosome 13 and the derivative (2:13) chromosome. Using available DNA probes from human chromosome 13 we find that the loci for retinoblastoma, esterase D, p7D2, pG24E6.8 and pG14E1.9 lie distally to the 13q14 breakpoint, whereas those for p7F12, pHU10 and pG2E3.1 all lie proximally. Thus we have defined a region of 13q14 of approximately 28mB which contains the breakpoint associated with this rearrangement.
Animals↗
Carrier detection and prenatal screening of the retinoblastoma gene.
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Female↗
Isolation and regional localisation of DNA sequences from a human chromosome 11-specific cosmid library.
A cosmid library has been prepared in the lorist-B vector from a mouse/human somatic cell hybrid containing region 11q23-11pter as the only human component. This chromosome region is stably maintained in the hybrid as a result of translocation onto one copy of mouse chromosome 13. Individual cosmids containing human DNA were isolated by their ability to hybridise with total human DNA, digested with either HindIII or EcoRI, and 33 individual unique sequences were identified. These fragments were then isolated and subcloned into the bluescribe plasmid vector. Regional localisation of these unique sequences was achieved using a panel of somatic cell hybrids containing different overlapping deletions of chromosome 11. The majority of the 33 mapped sequences derived from the long arm of chromosome 11. Two clones were located within the 11p13-p14 region, which is associated with a predisposition to Wilms' tumour. These probes supplement those already mapped to this chromosome and will assist in the generation of a detailed chromosome 11 linkage map.
Animals↗
Application of intragenic DNA probes in prenatal screening for retinoblastoma gene carriers in the United Kingdom.
Restriction fragment length polymorphisms (RFLPs) in 55 families affected by retinoblastoma have been studied using recombinant DNA probes derived from within the retinoblastoma predisposition gene. Only six families were uninformative for any of the DNA polymorphisms. The remaining 49 families can be offered prenatal screening. No obligate recombinations between any of the polymorphic loci and the retinoblastoma phenotype were observed. Four previously unknown cases of non-penetrance were identified. Prenatal testing for the inheritance of mutant alleles was performed in two cases and perinatal screening in two additional cases. One fetus inherited the normal allele from the affected parent and is therefore not at risk of retinoblastoma; the second fetus inherited the mutant allele and will require frequent screening for early detection of retinoblastoma. Both perinatal tests showed the absence of the mutant allele.
DNA Probes↗
Preferential loss of maternal alleles in sporadic Wilms' tumour.
Loss of heterozygosity at loci on the short arm of chromosome 11 has been reported in 31% (11/38) of Wilms' tumours in our series. Lymphoblastoid cell lines were prepared from the parents of 10/11 of the patients showing allele loss in their tumours. In 9 of the cases, where the parental origin of the alleles could be followed, it was the paternal alleles which were retained in the tumour. This preferential loss of the maternal alleles implies a role for genomic imprinting in the pathogenesis of Wilms' tumour.
Alleles↗
The nuclear oncoproteins: RB and p53.
A novel class of oncogene has been recognised whose loss-of-function results in the expression of the malignant phenotype. Two examples of such genes are the human retinoblastoma predisposition gene (RB1) and the gene encoding the cellular protein p53. These genes are thought to regulate and limit normal proliferation of cells and, as a consequence, can suppress tumorigenicity when introduced into transformed cells. They are hence frequently described as 'tumour suppressor genes'. Both RB1 and p53 gene products are bound by various transforming early proteins encoded by the DNA tumour viruses SV40, adenovirus and human papilloma virus. It is thought that they are thus sequestered and rendered inactive. Thus, a coherent model is emerging whereby inactivation, either by mutation of sequestration, of these tumour suppressor genes may contribute to natural and experimental carcinogenic processes.
Humans↗
Loss of heterozygosity in Wilms' tumour involves two distinct regions of chromosome 11.
Pairs of tumour and normal DNA samples from 38 Wilms' tumour patients have been investigated for loss of heterozygosity using 12 probes from chromosome 11. Allele loss was detected in only 11 cases (31%). Densitometric analysis showed that allele loss was not due to non-disjunction or hemizygous deletion, but rather to mitotic recombination or non-disjunction plus reduplication. Although the development of homozygosity sometimes involved the whole of the short arm of chromosome 11, in a few tumours allele loss was restricted to band 11p15 or 11p13 and distal sequences. This suggests mutations in two distinct regions play an important role in Wilms' tumorigenesis. There was no apparent correlation between loss of heterozygosity and tumour stage, age of presentation, or prior exposure to chemotherapy.
Alleles↗
A MspI RFLP associated with the human catalase gene.
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Catalase↗
The aniridia-Wilms' tumour association: molecular and genetic analysis of chromosome deletions on the short arm of chromosome 11.
We have analysed karyotypes and DNA from three patients with aniridia (congenital absence of irises) and Wilms' tumour. All three had constitutional deletions from the short arm of chromosome 11. The minimum region of overlap of the deletion involves a small region of band 11p13 presumed to contain the genetic loci responsible for both phenotypic abnormalities. Using cells from these patients, somatic cell hybrids with transformed mouse cells have been prepared. Individual subclones retaining either the deletion-11 chromosome or the normal chromosome 11, in addition to a variety of other human chromosomes, have been identified. The relative position of these breakpoints have been determined and the panel of hybrids has been used to map randomly-isolated 11p13 DNA sequences. The characterisation of these deletions has provided a useful panel of hybrids for random mapping strategies designed to identify the Wilms' and aniridia genes.
Cell Line↗
A somatic cell hybrid mapping panel for regional assignment of human chromosome 13 DNA sequences.
We have constructed somatic cell hybrids containing different overlapping deletions involving human chromosome 13. Cytogenetic characterisation of the breakpoints allowed division of the chromosome into six distinct regions. Molecular characterisation of these hybrids allowed regional assignment of anonymous DNA sequences, cDNAs, and isoenzyme variants and these hybrids should prove valuable in the analysis and isolation of genes and disease loci on chromosome 13.
Animals↗
One hundred years of retinoblastoma research. From the clinic to the gene and back again.
Retinoblastoma (RB) has provided the prototype for the study of hereditary predisposition to cancer. An intraocular tumour of young children, it has both hereditary and sporadic forms. The familial form of RB is inherited as an autosomal dominant with high penetrance. In a small group of patients the identification of a constitutional deletion on the long arm of chromosome 13 indicated the location of the critical gene in region 13q14 Close linkage between the hereditary, non-deletion form of RB and the esterase-D gene, which is also located in 13q14, demonstrated that all hereditary forms of RB are due to defects in a gene at this locus. Analysis of the development of homozygosity for region 13q14 in sporadic tumours subsequently confirmed that probably all RB tumors are due to mutations in a single gene, RB1. Using molecular biological techniques a candidate gene has been isolated which maps to region 13q14 and which shows structural re-arrangements within tumour cells. Predisposing, hereditary mutations have also been shown to involve this gene thereby providing strong evidence for its authenticity. The isolation of DNA sequences from within this gene, which identify restriction fragment length polymorphisms, means that it is now possible to use them to carry out pre-natal diagnosis and identify individuals at high risk to tumour development.
Carboxylesterase↗
Demonstration of bias in series of retinoblastoma.
A register of retinoblastoma is being compiled with the aim of complete ascertainment of all cases with a recorded diagnosis of retinoblastoma in the United Kingdom. Sources of ascertainment include patients seen at St Bartholomew's and Moorfields Eye Hospitals, cases recorded in regional cancer registries, and pathology reports. Ascertainment of the Hospital series is complete, but that of the rest of the country is still incomplete. Comparison between the proportions of bilateral and unilateral cases in an age cohort in the Hospital series and the country as a whole shows that the Hospital series is biased towards an excess of bilateral cases.
Eye Neoplasms↗
Genetic and cytogenetic analysis of patients showing reduced esterase-D levels and mental retardation from a survey of 500 individuals with retinoblastoma.
The authors have analysed the esterase-D levels in 500 retinoblastoma patients of whom 15 showed red cell enzyme activities of approximately 50% that of normal controls. Chromosome analysis of these 15 patients confirmed the presence of a deletion involving region 13q14 in all cases. Seven of the 15 cases had not previously been diagnosed and all of these showed sub-band deletions within 13q14. None of these seven patients were mentally retarded although the remaining eight who showed larger chromosome deletions demonstrated the full spectrum of psychomotor abnormalities associated with 13q deletions. Two other mentally retarded retinoblastoma patients with normal esterase-D activity showed no karyotypic abnormality, demonstrating that mental retardation cannot be taken to indicate a chromosome deletion in all cases. Eight of the 15 deletion cases were only unilaterally affected. The data presented in this article suggest that esterase-D quantitation could provide the primary means of detection of chromosome deletions in retinoblastoma patients.
Adult↗
Predisposition to retinoblastoma due to a translocation within the 4.7R locus.
A candidate for the retinoblastoma (Rb) predisposition gene, known as 4.7R, has recently been cloned. Authentication of this gene depends on abnormalities detected in either the genomic sequence or transcription products (or both) in Rb tumours and cell lines. We report a constitutional chromosome translocation, with a breakpoint lying within the putative retinoblastoma gene, from a patient with retinoblastoma; there is an associated small intragenic deletion. This structural rearrangement, which confers susceptibility to tumour formation, provides strong evidence that the 4.7R cDNA represents the Rb gene.
Adolescent↗