Similar abnormalities were also observed in the brains of Bbs2(-/-), Bbs4(-/-), and Bbs6(-/-) mice, establishing these neuroanatomical defects as a previously undescribed BBS mouse model phenotype.
The disorder showed statistically significant genetic linkage to the BBS4 locus on chromosome 15 in the affected siblings in two of the families, but the clinical features in these patients did not differ from the other cases of Bardet-Biedl syndrome.
This finding broadens the spectrum of clinical manifestations associated with BBS, confirms the role of BBS4 in olfaction, and lends support to the hypothesis that ciliary dysfunction is an important aspect of BBS pathogenesis.
To investigate the etiopathogenesis of BBS, we created a mouse null for one of the murine homologues, Bbs4, to assess the contribution of one gene to the pleiotropic murine Bbs phenotype.
We demonstrate that necdin and Magel2 bind to and prevent proteasomal degradation of Fez1, a fasciculation and elongation protein implicated in axonal outgrowth and kinesin-mediated transport, and also bind to the Bardet-Biedl syndrome (BBS) protein BBS4 in co-transfected cells.
We examined 3 pairs of siblings with Bardet-Biedl syndrome in whom 3 different mutations in the BBS4 gene were detected, 2 of which were homozygous for the mutation.