Identification of novel proteins synthesized in bone cells by antibody screening of a cDNA expression library

Novel proteins synthesize predominantly in bone have been identified by antibody screening of bone cell cDNA expression libraries. Two unique cDNAs were identified whose structures do not match any known nucleic acid or protein sequence in the NIH computer bank. The first cDNA clone, BP-I, encoded a mRNA of 2300 bases in size which was expressed at high levels in 17/2.8 rat osteosarcoma cells, rat calvarial bone cells and placenta. A second clone, BP-II, encoded a mRNA of 1500 bases which was expressed at high levels in 17/2.8 osteosarcoma cells and in salivary gland. Expression of both mRNAs in osteosarcoma cells was modulated by the calciotropic hormone, vitamin D. Southern blot analyses indicated that the two cDNAs represented distinct, single copy genes in the rat genome. These novel gene products may serve as potential new markers to study bone turnover in metabolic bone disease.