CBFA2T1, a gene rearranged in human leukemia, is a member of a multigene family

MTG8 (HGMW-approved symbol CBFA2T1) was originally identified as one of the loci involved in the t(8; 21)(q22;q22) of acute myeloid leukemia. We characterize two human MTG8-related genes, MTGR1 and MTGR2 (HGMW-approved symbols CBFA2T2 and CBFA2T3). The former is duplicated in mouse, one locus possibly being a retroposon. Multiple MTG8-related sequences are found in several vertebrate species, from fish to mammals, albeit not in a urodele. MTGR2 maps to 16q24 and, like MTG8 and MTGR1, is close to one of three loci encoding a syntrophin (dystrophin-associated proteins). Moreover, an alternative MTGR1 promoter/5' exon is contained within the alpha1-syntrophin locus. Thus, the two classes of genes may define novel paralogous groups. MTGR1 is expressed mainly in brain, while MTGR2 is expressed in the thymus and possibly in monocytes. Like MTG8, MTGR1 is transcribed into a number of isoforms due to alternative splicing of different 5' exons onto a common splice acceptor site. Comparison of the three predicted human MTG8-related polypeptides to their Drosophila counterpart (nervy) highlights four separate regions of sequence conservation that may correspond to distinct domains. The most NH2-terminal of these is proportionately more conserved among the human polypeptides, presumably due to specific structural/functional constraints.