Bardet-Biedl syndrome is characterised by usually severe pigmentary retinopathy, early-onset obesity, polydactyly, hypogenitalism, renal malformation and mental retardation []. Bardet-Biedl syndrome proteins (BBS1, BBS2, BBS4, BBS5, BBS7, BBS8/TTC8, BBS9 and BBIP10) form the BBSome complex, which may function as a coat complex required for sorting of specific membrane proteins to the primary cilia []. The ciliary trafficking function of BBSome is regulated by LZTFL1 (Leucine-zipper transcription factor-like 1) [].Primary cilia are ubiquitous cellular appendages that provide important sensory and signalling functions and their dysfunction underlies numerous human genetic disorders. The proteins disrupted in the human ciliary disorder Bardet-Biedl syndrome (BBS) are required for the localisation of G protein-coupled receptors to primary cilia on central neurons. The alteration of signalling caused by mislocalisation of ciliary signalling proteins underlies the BBS phenotype []. Of the 12 known BBS genes, BBS1 is the most commonly mutated [].This entry represents BBS4. It may participate in triallelic inheritance with BBS2 and BBS1 [].
Centrosomal protein of 131kDa (CEP131) is a cilium-specific protein required for cilium/flagellum formation []. In Drosophila, CEP131, also known as Azi1, functions in ciliogenesis and is involved in genome stability and centriole duplication [, ]. In mice, it mediates trafficking events necessary for spermiogenesis and male fertility []. It interacts with BBS4 (Bardet-Biedl syndrome 4) and regulates ciliary trafficking of the BBSome [].
