Evidence for a New Locus for Bardet Biedl Syndrome

Abstract

Abstract: : Purpose: Bardet–Biedl syndrome (BBS) is an autosomal recessive disorder characterized by obesity, retinopathy, polydactyly, renal and cardiac malformations, learning disabilities, and hypogenitalism. Eight BBS loci have been mapped, and eight genes have been identified. We investigate linkage and haplotype analysis in two consanguineous Tunisian families Methods: Haplotype and linkage analysis of two consanguineous families diagnosed BBS was scored with more than 24 polymorphic markers neighboring and surrounding the eight known BBS genes. Two–point lod scores were calculated. DNA from affected individuals from both families was amplified with primers specific for BBS1, BBS2, BBS4, BBS6, BBS7 and BBS8 genes and then sequenced by direct automated sequencing. Results: The combined haplotype analysis and linkage analysis in two Tunisian consanguineous families with BBS have excluded any linkage to any of the eight known BBS loci. Sequence analysis of BBS1, BBS2, BBS4, BBS6, BBS7 and BBS8 genes revealed no sequence alterations in their coding sequence. Conclusions: These results describe evidence for at least one new locus for BBS confirming the extreme genetic heterogeneity for this disease. The absence of alterations in six of the eight known BBS genes demonstrates that a new BBS locus is not involved in triallelic inheritance with these known genes.

Keywords: gene mapping • linkage analysis • retinitis