BMP-8

BMP8, also known as osteogenic protein 2 (OP2), was first isolated from a hippocampal library in a screen to identify relatives of BMP7/ OP1. BMPs are a family of structurally and functionally related proteins and represent a subfamily of the transforming growth factor β (TGFβ) superfamily. BMPs are involved in a wide range of processes including embryogenesis, tissue morphogenesis, cell differentiation and migration, and tumorigenesis. Cellular responses to BMPs are mediated by heterooligomeric complexes of type I and type II serine/threonine kinase receptors . BMP8a and BMP8b, produced from separate genes, share 98% aa sequence identity in human but only 74% in mouse within the mature regions. Human BMP8a is synthesized as a 402 aa precursor protein that is cleaved between Arg263 and Ala264 to release the Cterminal mature protein. Mature human BMP 8a shares 90% and 68% aa sequence identity with mouse mature BMP8a and 8b, respectively. BMP8a is expressed during pregnancy in the deciduum and trophoblast cells, by inner root sheath cells of developing hair follicles, and by the epididymis and spermatids). In the mouse it cooperates with BMP7 in the maintenance of spermatogenesis but is not required for the initiation of spermatogenesis (7, 8). BMP8b, in contrast, is required for both the initiation and maintenance of spermatogenesis. BMP8a is induced during osteoblast differentiation at the onset of mineralization and during the osteogenic phase of bone repair in osteoblasts and osteocytes (1012). BMP8a/b is also highly expressed in osteosarcomas.