Narrowing the position of the Werner syndrome locus by homozygosity analysis-extension of homozygosity analysis

Transcriptional activation by the Werner syndrome gene product in yeast

Werner syndrome (WS) is characterized by the premature occurrence of many age-related features. Before the cloning of the gene for WS (WRN), several reports suggested that transcriptional defects of genes may relate to the mechanisms of the occurrence of WS and natural aging. Because WRN, which encodes a helicase (WRN-H), has been cloned, we are attempting to clarify the mechanism of the transcriptional abnormalities found in WS cells, using WRN and WRN-H. In this article, we studied transcriptional activation of a promoter by WRN-H in a yeast assay system as a first step. The results showed that WRN-H functions as a transcriptional activator in the system. Furthermore, we performed additional transcriptional assays using various parts of WRN to define the critical region of WRN-H for transcriptional activation in yeast. The results revealed the critical region for the activation most likely mapped to the region of 315 to 403 aa. The region of 404 to 1309 aa may also effect activation in the presence of the critical region. The two regions contain an acidic domain, and the region of 404 to 1309 aa also contains a helicase domain. If this transcriptional activation by WRN-H occurs also in human cells in vivo, direct activation of the promoters by WRN-H could explain the results of somatic cell hybrid studies as well as the overexpressed genes detected in WS cells. However, our results should be interpreted with caution, because thus far, the transcriptional activation by WRN-H were only demonstrated using one promoter in a yeast system.

A deletion within the murine Werner syndrome helicase induces sensitivity to inhibitors of topoisomerase and loss of cellular proliferative capacity

Werner syndrome (WS) is an autosomal recessive disorder characterized by genomic instability and the premature onset of a number of age-related diseases. The gene responsible for WS encodes a member of the RecQ-like subfamily of DNA helicases. Here we show that its murine homologue maps to murine chromosome 8 in a region syntenic with the human WRN gene. We have deleted a segment of this gene and created Wrn-deficient embryonic stem (ES) cells and WS mice. While displaying reduced embryonic survival, live-born WS mice otherwise appear normal during their first year of life. Nonetheless, although several DNA repair systems are apparently intact in homozygous WS ES cells, such cells display a higher mutation rate and are significantly more sensitive to topoisomerase inhibitors (especially camptothecin) than are wild-type ES cells. Furthermore, mouse embryo fibroblasts derived from homozygous WS embryos show premature loss of proliferative capacity. At the molecular level, wild-type, but not mutant, WS protein copurifies through a series of centrifugation and chromatography steps with a multiprotein DNA replication complex.

Geneticists share the family jewels: how inbreeding has contributed to understanding hereditary skin disease

BACKGROUND

Offspring resulting from consanguineous marriages have been important in advancing research in genodermatoses.

OBJECTIVE

The concepts of consanguinity and inbreeding are reviewed and their contributions to research in hereditary skin diseases explained.

METHODS

Examples are given in which inbred individuals with hereditary skin disease have increased our knowledge of skin disease genetics.

RESULTS

An enhanced understanding of the genetics of xeroderma pigmentosum, lamellar ichthyosis, and Werner's syndrome, among others, has arisen from the observation of populations and families in which inbreeding has occurred.

CONCLUSION

Populations practicing inbreeding and consanguineous marriages in generally outbred populations have provided important observations for determining the inheritance pattern of several genodermatoses and for identifying the responsible genes.

Molecular and epidemiological studies of Werner syndrome in the Japanese population

Werner syndrome (WS) is an autosomal recessive genetic disease characterized by many age-related features. The gene responsible for WS (WRN) has been isolated and contains a helicase domain, but its function is unknown. Six different mutations throughout the WRN gene have been reported in the Japanese population. We have studied whether patients with a specific mutation exhibit distinct phenotypes from others. Fourteen patients with different mutations showed almost the same signs and symptoms and, therefore, the C terminal part of the product appears to be crucial for its functions, although other parts may be important as well. Haplotype analyses using 13 microsatellites covering the 2.8-3.0 cM WRN region showed that two out of six different mutations had founder chromosomes. These two founder chromosomes may be evenly distributed throughout the western part of Japan, suggesting that these mutations go back to a time earlier than 1400 years ago.

A high-density STS map based on a single contig of YAC and P1 clones in the chromosome 8p12-p21 region

We have constructed a yeast artificial chromosome (YAC) and P1 contig in the 8p12-p21 region. The contig comprises 16 overlapping YAC clones and 44 overlapping P1 clones. Twelve dinucleotide-repeat polymorphic sequence-tagged site (STS)-markers that were previously isolated mainly from these YAC and P1 clones were genetically mapped. A total of 46 nonpolymorphic STS markers were newly established mainly from the YAC and P1 clone end fragments, and 28 of the 46 nonpolymorphic STSs, as well as the 12 polymorphic STSs, were also mapped physically onto the contig based on STS content analysis of YAC pools and of the P1 and YAC clones. As a result, the YAC and P1 clones were assembled into a single contig covering a minimum of 1.5 Mb physically and 2.8 cM genetically with 12 polymorphic and 28 nonpolymorphic STSs within the 8p12-p21 region. Average STS spacing in the contig was estimated to be 40 kb/STS. In addition, further characterization of the contig suggested that this contig includes a region where genetic recombination occurs frequently. Thus, the resulting cloned region, together with densely mapped STS markers on the contig, should help to promote our understanding of this region.