The existence of Usher syndrome type III proven by assignment of its locus to chromosome 3q by linkage
- Univ. of Helsinki (Finland); and others
Usher syndromes (USH) are genetically and clinically heterogeneous autosomal recessive disorders with combined visual and hearing loss. Usher syndrome type III (USH3) is characterized by progressive bilateral sensorineural deafness and progressive pigmentary retinopathy leading to blindness. USH3 has been conservatively estimated to comprise 2% of the three clinical USH types, and its existence has even been questioned. However, based on clinical criteria, in Finland 42% of USH patients have USH3 suggesting gene enrichment by a founder effect. Genes whose defects cause USH have so far been mapped to four different locations in three chromosomes. We have excluded the previously mapped USH regions as the site of USH3 disease locus. Systematic search for USH3 by genetic linkage analyses of 11 multiple affected families using highly polymorphic microsatellite markers revealed significant linkage with five markers mapping to chromosome 3q. Two-point lod scores at zero recombination distance were 5.24 for D3S1308, and 7.71 for D3S1299, respectively. Multipoint linkage analysis gave a maximum lod score of 8.68 at D3S1299 assigning USH3 to the 4 cM interval between markers D3S1555 and D3S1279 in 3q21-25. Of 20 parental disease chromosomes, 15 had identical alleles at three marker loci covering 3 cM genetic distance and the putative USH3 mutation. These findings prove the existence of USH3 as a distinct entity, pinpoint a fifth USH locus, and suggest enrichment of a major mutation in the isolated Finnish population.
- OSTI ID:
- 133317
- Report Number(s):
- CONF-941009--
- Journal Information:
- American Journal of Human Genetics, Journal Name: American Journal of Human Genetics Journal Issue: Suppl.3 Vol. 55; ISSN AJHGAG; ISSN 0002-9297
- Country of Publication:
- United States
- Language:
- English
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