(1999) narrowed the assignment of the USH3 gene to the interval between D3S1299 and D3S3625. In the course of their study of this family, Adato et al. The authors suggested a possible synergistic interaction between MYO7A and the USH3 gene product that might increase the severity of the deafness as part of the clinical symptoms associated with USH3. (1999) found a double mutation of the MYO7A gene ( 276903), which is responsible for USH1B, on 1 maternal chromosome in the brother with the more severe USH1 phenotype the mother and 2 unaffected sibs also carried the double mutation. (1997), in which the 2 affected brothers had different Usher syndrome phenotypes: one had typical USH3 phenotype, whereas the other had typical USH1 ( 276900) phenotype. (1999) studied a nonconsanguineous Jewish Yemenite family with 2 affected and 6 healthy sibs, originally reported by Adato et al. (1998) with Usher syndrome type III, Joensuu et al. (1996) and the Italian family reported by Gasparini et al. In the 2 Finnish families reported by Sankila et al. (1998) reported linkage analysis of an Italian family with Usher syndrome type III and confirmed linkage at 3q24-q25 with a maximum lod score obtained with marker D3S1299 (maximum lod = 2.43 at theta = 0.00). The profilin-2 gene (PFN2 176590) was mapped to the vicinity but was excluded as a candidate for USH3 by sequencing. By analysis of linkage disequilibrium and historical recombinations in 77 USH3 chromosomes, the location of the Finnish USH3 mutation was narrowed to an interval of approximately 1 cM between markers D3S1299 and D3S3625. (1996) typed a total of 32 pedigrees from a geographically isolated Finnish founder population for polymorphisms in the USH3 region of chromosome 3. They stated that this was the fifth distinctive form of Usher syndrome to be identified. Of 20 parental disease chromosomes, 15 had identical alleles at 3 marker loci covering a 3-cM genetic distance, including the putative USH3 locus. Using highly polymorphic microsatellite markers for a systematic search for the USH3 locus by genetic linkage analyses of 11 multiply affected families, they assigned the disease locus to 3q21-q25. ![]() ( 1994, 1995) excluded previous chromosomal sites at which Usher syndrome had been mapped. In Finnish families segregating Usher syndrome type III, Sankila et al. ![]() Usher syndrome, type IIC, GPR98/PDZD7 digenic Usher syndrome, type 2C, GPR98/PDZD7 digenic
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