Structure and expression of mitsugumin29 gene.

Recently mitsugumin29 unique to the triad junction in skeletal muscle was identified as a novel member of the synaptophysin family; the members of this family have four transmembrane segments and are distributed on intracellular vesicles. In this study, we isolated and analyzed mouse mitsugumin29 cDNA and genomic DNA containing the gene. The mitsugumin29 gene mapped to the mouse chromosome 3 F3-H2 is closely related to the synaptophysin gene in exon-intron organization, which indicates their intimate relationship in molecular evolution. RNA blot hybridization and immunoblot analysis revealed that mitsugumin29 is expressed abundantly in skeletal muscle and at lower levels in the kidney. Immunofluorescence microscopy demonstrated that mitsugumin29 exists specifically in cytoplasmic regions of the proximal and distal tubule cells in the kidney. The results obtained may suggest that mitsugumin29 is involved in the formation of specialized endoplasmic reticulum systems in skeletal muscle and renal tubule cells.