Demonstration of Genetic Interactions between TRIM32 and other Bardet-Biedl Syndrome Genes. M.K. Tayeh^1,2,3, H-J. Yen^1,2,3, R.F. Mullins⁴, A.P. Chiang^1,2,3, J.S. Beck^1,3, C.C. Searby^1,3, T.A. Westfall⁵, H. Griesback⁵, E.M. Stone^3,4, D.C. Slusarski⁵, V.C. Sheffield^1,3. 1) Dept Pediatrics, Univ Iowa, Iowa City, IA; 2) Genetics Ph.D. program, Univ Iowa, Iowa City, IA; 3) Howard Hughes Medical Institute; 4) Dept Ophthalmology, Univ Iowa, Iowa City, IA; 5) Dept Biology, Univ Iowa, Iowa City, IA.
   Bardet Biedl syndrome (BBS) is a pleiotropic, genetically heterogeneous, autosomal recessive disorder with the primary clinical features of obesity, retinopathy, polydactyly, learning disabilities, renal abnormalities and hypogenitalism. To date, 11 BBS genes have been identified and experiments suggest that BBS proteins play a role in the function of cilia and intracellular transport. We have used antisense oligonucleotides (morpholinos) for knock down of BBS gene expression in zebrafish to demonstrate a role for BBS genes in cilia maintenance and retrograde intracellular transport, as well as to evaluate novel BBS candidate genes. In addition, we have used the zebrafish model system to investigate genetic interactions between paired combinations of BBS genes. Interactions in the zebrafish were analyzed by double knock down of BBS genes using pair wise co-injection of low dose BBS morpholinos. Injected embryos were analyzed for cilia and intracellular transport defects, as well as other abnormalities. Of the 28 possible paired combinations of eight BBS genes (BBS1-BBS8), we detected only two combinations of BBS gene double knockdowns that resulted in evidence of genetic interaction in the zebrafish model system. We recently identified TRIM32, an E3 ubiquitin ligase gene, as BBS11. We investigated genetic interactions between the zebrafish orthologue of TRIM32 and other BBS genes. Our data demonstrate interactions between zebrafish trim32 and multiple other BBS genes. These data suggest a likely role for TRIM32 in the ubiquitination of BBS gene products and indicate a possible role for TRIM32 in the modification of BBS phenotypes in human patients.