Phemx, a novel mouse gene expressed in hematopoietic cells maps to the imprinted cluster on distal chromosome 7

Phemx (Pan hematopoietic expression) is a novel murine gene expressed in de velopmentally regulated sites of hematopoiesis from early in embryogenesis through adulthood. Phemx is expressed in hematopoietic progenitors and matu re cells of the three main hematopoietic lineages. Conceptual translation o f the murine Phemx cDNA predicts a 25-kDa polypeptide with four hydrophobic regions and several potential phosphorylation sites, suggestive of a trans membrane protein involved in cell signaling. The PHEMX protein is structura lly similar to tetraspanin CD81 (TAPA-1), a transmembrane protein involved in leukocyte activation, adhesion, and proliferation. Phemx maps to the dis tal region of chromosome 7, a segment of the mouse genome that contains a c luster of genes that exhibit genomic imprinting, However, imprinting analys is of Phemx at the whole organ level shows that it is biallelically express ed, suggesting that mechanisms leading to monoallelic expression are not im posed at this locus. The human PHEMX ortholog is specifically expressed in hematopoietic organs and tissues and, in contrast to murine Phemx, undergoe s alternative splicing. The unique mode and range of Phemx expression sugge st that it plays a role in hematopoietic cell function. (C) 2000 Academic P ress.