A novel mutation in the mitochondrial tRNA(Ser(UCN)) gene in a family with non-syndromic sensorineural hearing impairment.

We describe a family with non-syndromic sensorineural hearing impairment inherited in a manner consistent with maternal transmission. Affected members were found to have a novel heteroplasmic mtDNA mutation, T7510C, in the tRNA(Ser(UCN)) gene. This mutation was not found in 661 controls, is well conserved between species, and disrupts base pairing in the acceptor stem of the tRNA, making it the probable cause of hearing impairment in this family. Sequencing of the other mitochondrial tRNA genes did not show any other pathogenic mutations. Four other mutations causing hearing impairment have been reported in the tRNA(Ser(UCN)) gene, two having been shown to affect tRNA(Ser(UCN)) levels. With increasing numbers of reports of mtDNA mutations causing hearing impairment, screening for such mutations should be considered in all cases unless mitochondrial inheritance can be excluded for certain.

Women's subjective experience of hysterectomy.

This paper presents data on the experience of hysterectomy from a sample of 656 women aged between 30 and 50 years recruited from patients of a random sample of 50 general practices in Perth. Respondents were identified as women who: had undergone hysterectomy for reasons other than cancer; were affected by gynaecological conditions; had neither gynaecological problems nor had undergone hysterectomy. Respondents voluntarily completed a self-administered questionnaire which covered demographic information, general health, gynaecological problems and hysterectomy, sexual activities, and family relationships. Formal measures of depression and self-esteem were included. The main concern was with the psychological and social outcomes of hysterectomy rather than its physical results. The findings showed that of 107 women who had undergone hysterectomy, only two had negative comments about the outcome. There were significant effects on both work and sexual relationships for women in the gynaecological condition group, with 52 per cent reporting adverse effects on work and 46 per cent believing that their sexuality was affected. Few women regarded the uterus as 'essential to femininity or womanhood' and very few saw it as affecting sexuality. Women in the hysterectomy group reported that their satisfaction with sexual activity had improved, whereas those with gynaecological conditions believed that it had deteriorated. Depression and self-esteem scores were significantly worse for women with gynaecological conditions.

Enzymatic methods for mutation scanning.

Enzymatic methods for mutation scanning still lack the sensitivity and specificity of the chemical cleavage of mismatch method. However developments in our understanding of the mismatch recognition process should lead to improvements. Several promising candidates exist with potential for more specific and sensitive mutation detection.

Analysis of the mismatch and insertion/deletion binding properties of Thermus thermophilus, HB8, MutS.

The methyl-directed long patch repair pathway in Escherichia coli is involved in increasing the fidelity of replication specific repair of DNA polymerase incorporation errors. This pathway is mediated by three gene products, MutS, MutL, and MutH, which are conserved in higher eukaryotes. Mutations in human homologues of these proteins have been shown to be implicated in hereditary non-polyposis colorectal cancer (HNPCC). A MutS homologue has recently been identified in the extremely thermophilic bacterium, Thermus thermophilus. Here we describe analysis of the binding properties of this protein, which has indicated it can identify all specific base mismatches as well as one, two and three base pair insertion/deletion mutations. We therefore believe this protein may be generally useful for applications involving mismatch detection.

A carboxy terminal domain of the hMSH-2 gene product is sufficient for binding specific mismatched oligonucleotides.

The human MSH-2 gene product is a member of a highly conserved family of proteins which are involved in post-replication mismatch repair. hMSH-2 is homologous to Escherichia coli (E. coli) MutS and Sacchromyces cerevisiae MSH-1 and MSH-2 proteins, which recognise heteroduplex DNA at the sites of all single base mismatches and deletions or insertions up to 4 base pairs. hMSH-2 is one of the hereditary non-polyposis colorectal cancer (HNPCC) tumor suppressor genes, and maps to human chromosome 2p16. Alterations in the coding region of the hMSH-2 gene result in a mutator phenotype with marked instability of microsatellite sequences, indicative of a deficiency in DNA repair. It has been shown that purified hMSH-2 binds specifically to nucleotide mismatches in double-stranded DNA. Here we demonstrate that a region of high homology between the members of this class of proteins contains a type A nucleotide binding site consensus sequence which has ATPase activity and is sufficient to bind DNA containing specific mismatched residues.

Mutational analysis of the nucleotide binding domain of the mismatch repair enzyme hMSH-2.

The genes involved in postreplicative DNA mismatch repair are a highly conserved family of proteins. In humans, germline mutations in these genes (hMSH-2, hMLH-1, hPMS-1, and hPMS-2) have been implicated in hereditary nonpolyposis colorectal cancer (HNPCC). We have previously shown that a region of high homology between the members of this class of proteins in different species contains a type A nucleotide binding site consensus sequence which has ATPase activity and is sufficient to bind DNA containing specific mismatched residues (1). To identify residues which are necessary for this activity, we have created a range of mutants containing amino acid substitutions within the nucleotide binding domain of hMSH-2. These mutants have been expressed and assessed for ATPase activity and their ability to identify mismatch-containing DNA. Here we demonstrate that a variant protein which has the conserved residue Lys 675 within the nucleotide binding consensus sequence altered to an alanine has severely impaired ATPase activity and is unable to bind DNA containing specific mismatched residues.

Mapping the minimal domain of hMSH-2 sufficient for binding mismatched oligonucleotides.

The human MSH-2 gene product is a member of a highly conserved family of proteins involved in post-replication mismatch repair. Germline mutations in this gene have been implicated in hereditary non-polyposis colorectal cancer (HNPCC). Alterations in the coding region of the hMSH-2 gene result in a mutator phenotype with marked instability of microsatellite sequences, indicative of a deficiency in DNA repair. We have previously shown that a region of high homology between MutS proteins of different species containing a nucleotide binding domain, is sufficient to bind DNA containing specific mismatched residues. In order to determine the minimal domain of hMSH-2 necessary for binding mismatch-containing oligonucleotides, deletion analysis of the C-terminal region was performed. We have constructed a 5' and 3' deletion series, expressed each deletion as a bacterial fusion protein and assessed it for ATPase activity and its ability to identify mismatch containing DNA. Here we demonstrate that a 585 bp fragment encoding 195 amino acids within the C-terminal domain of hMSH-2 is sufficient to bind to DNA containing mismatches.