A NOVEL GENE IBA1 IN THE MAJOR HISTOCOMPATIBILITY COMPLEX CLASS-III REGION ENCODING AN EF HAND PROTEIN EXPRESSED IN A MONOCYTIC LINEAGE

We successfully isolated a rat cDNA clone encoding a novel EF hand pro tein with a molecular weight of about 17 kDa and designated this gene iba1 (ionized calcium binding adapter molecule 1). The genomic copy of the iba1 gene was located within a segment of the major histocompatib ility complex class III region between the Bat2 and TNF alpha genes. T he iba1 gene was shown to be highly expressed in testis and spleen, bu t weakly expressed in brain, lung, and kidney. Among brain cells, the iba1 gene was specifically expressed in microglia. A screening of hemo poietic cell lines showed that the Iba1 protein was clearly expressed in monoblastic cell lines but only very weakly expressed in myeloid ce ll lines. Ibal protein is therefore suggested to act as an adapter mol ecule, mediating calcium signals that may function in a monocytic line age including microglia. (C) 1996 Academic Press, Inc.