Plasmolipin: genomic structure, chromosomal localization, protein expression pattern, and putative association with Bardet-Biedl syndrome

Plasmolipin is a membrane protein and belongs to the tetraspan molecule (4T M) family, an expanding group of myelin proteins many of which could be lin ked to human hereditary demyelinating neuropathies. We have cloned and sequ enced the mouse plasmolipin gene, revealing the common organization of the 4TM gene group with four exons and a large first intron. Western blot analy sis with an antibody raised against the C-terminal intracellular part of th e protein showed that plasmolipin is expressed not only in the nervous syst em and kidney, but also in a number of other tissues such as thymus, testis , lung, and thyroid a and. By means of radiation hybrid mapping and FISH an alysis, we could localize the human plasmolipin gene to Chromosome 16q13 wi thin the putative region of the Bardet-Biedl syndrome type 2 (BBS2) gene lo cus. BBS2 is a clinically and genetically heterogeneous group of disorders resulting in rod-cone dystrophy, obesity, postaxial polydactyly, renal dysf unction, and mental retardation, which were very recently associated with a novel gene designated BBS2. With respect to intrafamiliar variations in th e manifestation of BBS, we suggest that plasmolipin might be either another candidate gene or a modifier of the BBS2 phenotype.