Isolation, tissue distribution, and chromosomal localization of a novel testis-specific human four-transmembrane gene related to CD20 and Fc epsilon RI-beta

CD20 and the beta subunit of the high affinity receptor for IgE (Fc epsilon RI beta) are related four-transmembrane molecules that are expressed on th e surface of hematopoietic cells and play crucial roles in signal transduct ion. Herein, we report the identification and characterization of a human g ene, TETM4 that encodes a novel four-transmembrane protein related to CD20 and Fc epsilon RI beta. The predicted TETM4 protein is 200 amino acids and contains four putative transmembrane regions, N- and C-terminal cytoplasmic domains, and three inter-transmembrane loop regions. TETM4 shows 31.0 and 23.2% overall identity with CD20 and Fc epsilon RI beta respectively, with the highest identity in the transmembrane regions, whereas the N- and C-ter mini and inter-transmembrane loops are more divergent. Northern blot and RT -PCR analysis suggest that TETM4 mRNA has a highly restricted tissue distri bution, being expressed selectively in the testis, Using fluorescence in si tu hybridization and radiation hybrid analysis, the TETM4 gene has been loc alized to chromosome 11q12. The genes for CD20 and Fc epsilon RI beta have also been mapped to the same region of chromosome 11 (11q12-13.1), suggesti ng that these genes have evolved by duplication to form a family of four-tr ansmembrane genes. TETM4 is the first nonhematopoietic member of the CD20/F c epsilon RI beta family, and like its hematopoietic-specific relatives, it may be involved in signal transduction as a component of a multimeric rece ptor complex. (C) 2001 Academic Press.