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A subgroup of trinucleotide repeat diseases result from abnormal expansions of CAG repeats which are translated into polyglutamine stretches. As yet there is little understanding of how the polyglutamines function either normally, or when expanded. We have investigated these sequences in the Machado-Joseph disease, androgen receptor and spinocerebellar ataxia type 1 genes in humans and other primates. None of the 748 normal chromosomes that were examined had more than 34 uninterrupted glutamine codons in the Machado-Joseph disease gene. Similarly, no normal alleles with more than 39 uninterrupted glutamine codons have been reported for the other disease genes associated with polyglutamine expansions. Sequence analyses of the repeats in primates revealed shorter polyglutamine stretches in some of the non-human primates at all three loci and marked diversions from the expected polyglutamines in the orang-utan Machado-Joseph gene and in the marmoset spinocerebellar ataxia type 1 gene. These data suggest that conservation of these polyglutamine stretches may not always be necessary for normal gene function.

The discovery of the intragenic delta 2642 deletion/insertion polymorphism in the Huntington's disease (HD) gene provides a tool to explore HD evolution, as the deletion is rare in normal chromosomes but overrepresented in HD chromosomes. Thus, delta 2642 deletion alleles were thought to mark normal chromosomes that are particularly prone to becoming HD chromosomes. We have examined this polymorphism in a range of human and non-human primate populations. Our results suggest that the deletion event probably occurred in the human lineage on a chromosome with a CAG allele length at the upper end of the normal size range, as the deletion seemed to be only associated with human chromosomes with 20 or more repeats. These deletion chromosomes are prone to expansion into the HD range because they are at the upper end of the normal range. These data explain the apparent 'founder' HD haplotype defined by the deletion and suggest that chromosomes carrying the deletion are no more mutable than non-deletion chromosomes with similar sized CAG repeats.

The open reading frame of the SRY gene has been examined in a series of 22 XY females with clinically defined pure gonadal dysgenesis by direct sequencing of biotinylated PCR product bound to streptavidin coated beads. Amongst the 22 XY females examined, five (two of whom are sisters) were found to have single base changes all within the highly conserved DNA binding (or HMG box) domain. In the remaining 17 cases, the SRY gene sequence was indistinguishable from that found in normal males. In three of the XY females with point mutations, the altered amino acids occur in highly conserved positions leading to non-conservative changes (Arg to Gly at position 5, Met to Thr at position 21 and Arg to Trp at position 76). Examination of the SRY gene from the father's Y chromosome has shown that the mutations at position 5 in patient SHM60 and position 21 in patient HN31 have arisen de novo. In the case of the two sibs, both have identical mutations where a C to T transition in codon 17 has created a TAG termination signal, thus suggesting that the deceased father is likely to be a gonadal mosaic for the mutation. In the case of the mutations at positions 17 and 76, the fathers are not available for investigation and so it has not been possible to determine whether the changes are de novo. These data indicate that the majority of XY females with pure gonadal dysgenesis owe their sex-reversed phenotype to mutations in as yet uncharacterised segments of the SRY gene, or, at other loci acting early in the sex-determining pathway.

cDNA clones from a human adult testis cDNA library were isolated and sequenced as part of a programme to produce expressed sequence tags (ESTs). ESTs were used routinely to search DNA and protein sequence databases. One clone (142) showed 60% identity to the Bacillus subtilis glycerol kinase gene at both the DNA and amino acid sequence levels. Analysis of DNA from somatic cell hybrids carrying deleted X chromosomes, has shown that clone 142 detects homologous sequences between Xp21.2-p22.1 (the interval containing the locus responsible for glycerol kinase deficiency--GKD). These sequences are deleted in two patients with GKD. Clone 142 also detects homologous sequences on Xq and at several autosomal loci. The sequences of clone 142 and two further cDNA clones isolated from a human foetal brain cDNA library are presented.

Von Hippel-Lindau (VHL) disease is a dominantly inherited familial cancer syndrome characterised by the development of retinal and central nervous system haemangioblastomas, renal cell carcinoma and phaeochromocytoma. The gene for VHL disease has been mapped to chromosome 3p25-p26 and presymptomatic diagnosis using linked DNA markers is available. We have previously mapped the VHL disease gene to a 4 cM interval between D3S1250 and D3S18. To increase access to presymptomatic diagnosis and to accelerate progress towards isolating the VHL disease gene we attempted to identify microsatellite DNA markers linked to the disease gene by genetic linkage analysis in 29 families. We found significant linkage between the VHL disease gene and dinucleotide (CA) repeat polymorphisms at D3S1038 (Zmax = 22.24 at theta = 0.01, CI 0.0001-0.06), D3S1110 (Zmax = 11.32 at theta = 0.07, CI 0.03-0.14) and D3S651 (Zmax = 7.73 at theta = 0.04, CI 0.008-0.13). We localised D3S1038 between D3S1250 and D3S601, and mapped D3S1110 and D3S651 centromeric to D3S1250. Multipoint linkage analysis mapped the VHL disease locus between D3S1038 and D3S18 with the maximum likelihood at D3S601. There was no evidence of locus heterogeneity. This study has (i) identified three microsatellite DNA markers in chromosome 3p25 linked to the VHL disease gene and (ii) narrowed the target region for the isolation of the VHL disease gene by positional cloning techniques. These findings will improve the management of families with VHL disease by improving the accuracy and availability of presymptomatic diagnosis using linked DNA markers, and will accelerate progress towards isolating the VHL disease gene.

41 Y-linked DNA probes that detect sequences on the Y chromosome long arm have been used to analyse genomic DNA from a series of 23 patients with deletions of Yq. Southern blot analysis has differentiated 15 distinct breakpoints, which divide Yq into 14 mapping intervals. From the pattern of DNA sequences present in each patient, it has been possible to produce a congruent deletion map, with the exception of two cases which are not compatible with the consensus order. These patients can be explained by the presence of inversion polymorphisms on Yq in the general population or by complex rearrangements induced during the formation of the deleted chromosomes. The distribution of sequences on the Y long arm has defined distinct regions of homology with autosomes, the Y short arm and the long and short arms of the X. A number of the patients have been typed for the presence or absence of H-Y antigen (as determined by the cytotoxic T-cell assay) and it has been possible, from analysis of informative cases, to assign the locus to the proximal region of the Yq euchromatin.

VHL disease is a dominantly inherited familial cancer syndrome with variable expression and age-dependent penetrance. The diagnosis of isolated cases is often delayed compared with familial cases, and estimates of the new mutation rate have varied more than 20-fold. To investigate the frequency and origin of de novo VHL gene mutations we have analysed: (i) families with identical mutations to determine if there is a common haplotype, and (ii) apparent new mutation cases to determine whether the clinical diagnosis of such cases is reliable and to define the parental origin of de novo VHL gene mutations. Haplotyping of 12 VHL mutations occurring in two or more families (total 42 kindreds) revealed that for most mutations there was no evidence of a founder effect. A marked bias for a paternal origin of new mutations has been reported in other familial cancer syndromes such as neurofibromatosis type 1 (NF1), multiple endocrine neoplasia (MEN) 2B and bilateral retinoblastoma, but it is unclear whether this bias results from a greater susceptibility for mutagenesis during male gametogenesis because of the larger number of cell divisions compared with that in oogenesis, or from genomic imprinting effects. Analysis of 13 de novo VHL mutations in which the parent of origin could be established, showed no evidence for a bias for a paternal origin (seven paternal, six maternal), and differed significantly from that reported in NF1, MEN2B and bilateral retinoblastoma. This result demonstrates that an increased susceptibility to paternal allele mutation is not a universal finding in autosomal genetic diseases and that the origin of new mutations may be influenced by both genomic imprinting effects and the increased number of cell divisions in spermatogenesis compared with oogenesis.

Loss of heterozygosity (LOH) studies have suggested that somatic mutations of a tumour suppressor gene or genes on chromosome 3p are a critical event in the pathogenesis of non-familial renal cell carcinoma (RCC). Germline mutations of the von Hippel-Lindau (VHL) disease gene predispose to early onset and multifocal clear cell renal cell carcinoma, and the mechanism of tumorigenesis in VHL disease is consistent with a one-hit mutation model. To investigate the role of somatic VHL gene mutations in non-familial RCC, we analysed 99 primary RCC for VHL gene mutations by SSCP and heteroduplex analysis. Somatic VHL gene mutations were identified in 30 of 65 (46%) sporadic RCC with chromosome 3p allele loss and one of 34 (3%) tumours with no LOH for chromosome 3p. The VHL gene mutations were heterogeneous (17 frameshift deletions, eight missense mutations, four frameshift insertions, one nonsense and one splice site mutation), but no mutations were detected in the first 120 codons of cloned coding sequence. Most RCCs with somatic VHL mutations (23 of 27 (85%) informative cases) had chromosome 3p25 allele loss in the region of the VHL gene so that both alleles of the VHL gene had been inactivated as expected from a two-hit model of tumorigenesis. Detailed histopathology was available for 59 of the tumours investigated: 18 of 43 (42%) RCC with a clear cell appearance had a somatic VHL gene mutation but none of 16 non-clear cell RCC (eight chromophilic, three chromophobe and five oncocytoma) (chi2 = 7.77, P < 0.025).(ABSTRACT TRUNCATED AT 250 WORDS)

The human glycerol kinase gene family consists of at least six genomic loci, four of which encode expressed sequences. The X-linked gene responsible for GKD maps to Xp21.3. Analysis of cosmid and YAC clones shows that this locus is in excess of 50 kbp, and is comprised of 19 exons. In contrast, the remaining members of the gene family, on chromosomes 1, 4 and Xq, appear to be organized as intronless genes. Northern analysis shows expression of GK transcripts of three sizes in a wide range of adult tissues. Only the smallest hybridizing species is present in testis where it occurs at an elevated level. Two different testis transcripts have been identified and both of these originate from chromosome 4.

Von Hippel-Lindau (VHL) disease is a dominantly inherited familial cancer syndrome predisposing to a variety of malignant and benign neoplasms, most frequently retinal, cerebellar and spinal haemangioblastoma, renal cell carcinoma, phaeochromocytoma and pancreatic tumours. We have previously detected large germline deletions by Southern analysis and pulsed field gel electrophoresis in 19% and 3% of VHL patients respectively. We have now investigated 94 VHL patients without large deletions for intragenic mutations using single strand conformation polymorphism and heteroduplex analysis. Forty different mutations were identified in 55 unrelated kindreds. A wide variety of mutations were detected including missense (n = 19), nonsense (n = 6), frameshift deletions or insertions (n = 12), in frame deletions (n = 2) and a splice donor site mutation (n = 1). The two most frequent mutations, were missense mutations at codon 238 (Arg--Gln and Arg--Trp) and were detected in five and four unrelated kindreds, respectively. VHL disease shows marked phenotypic variability and although phaeochromocytoma occurs in only about 7% of patients, marked interfamilial differences are observed. We examined the relationship between VHL gene mutations and phenotype in 65 kindreds. Large deletions or intragenic mutations predicted to cause a truncated protein were found in 36 of 53 families without phaeochromocytoma but only two of 12 families with phaeochromocytoma (chi 2 = 8.58; P0.01). Of 12 families with phaeochromocytoma 10 had missense mutations compared with 13 of 53 kindreds without phaeochromocytoma (chi 2 = 12.33; P0.001). In particular, substitution of an arginine at codon 238 (Arg--Trp or Arg--Gln) was associated with a high risk (62%) of phaeochromocytoma.(ABSTRACT TRUNCATED AT 250 WORDS)

Von Hippel-Lindau disease is a dominantly inherited familial cancer syndrome characterised by the development of retinal angiomatosis, cerebellar and spinal hemangioblastoma, renal cell carcinoma, phaeochromocytoma and pancreatic tumours. A cDNA (g7) which detects frequent genomic rearrangements in VHL disease patients on Southern analysis, and contains the partial coding sequence of the VHL gene has been isolated recently. To characterise the nature of the genomic rearrangements in VHL disease we initially screened 116 patients with VHL disease and identified 22 patients (19%) with abnormal fragments in EcoR1 digested DNA probes with g7. We then established that the coding sequence contained within g7 is represented in 3 exons, and design exon specific probes to investigate the 22 patients with genomic rearrangements. All 22 patients were demonstrated to have germline deletions, but the deletions were heterogeneous with 7 patients having deletions confined to the 5' exon 1, and 8 with nonoverlapping deletions of exon 3. In 7 unrelated patients, including 2 new mutations, the germline deletions were similar in size and position. There was no relationship between the clinical phenotype and the deletion of individual exons. Although phaeochromocytoma was less frequent in kindreds with germline deletions than those without detectable deletions, the difference was not statistically significant (1/19 versus 16/72 respectively, chi 2 = 1.84 p > 0.1).

Von Hippel-Lindau (VHL) disease is a dominantly inherited familial cancer syndrome in which affected individuals have a greatly increased predisposition to the development of haemangioblastomas of the central nervous system and retina, renal cell carcinoma and phaeochromocytoma. The VHL gene has been mapped to chromosome 3p25-p26 by genetic linkage studies and we have previously demonstrated that the VHL gene is tightly linked to the D3S601 locus (Zmax = 18.86 at theta = 0.0) suggesting that D3S601 maps close to the VHL disease gene. We have constructed a long range physical map around D3S601 and screened 91 VHL patients from 80 kindreds for germline rearrangements using pulsed field gel electrophoresis. Two patients showed abnormal fragments in Mlul digested DNA probed with D3S601. Further analysis was consistent with both patients having germline deletions (approximately 120 kb and 50 kb) telomeric to D3S601. These results have (i) established the position of the VHL disease gene with respect to D3S601, (ii) refined the localisation of the VHL disease gene to a small region (approximately 50 kb) of chromosome 3p25-p26 and (iii) excluded the plasma membrane Ca(+)+-transporting ATPase isoform 2 (PMCA-2) gene as a candidate gene for VHL disease.