ISOLATION AND EXPRESSION STUDY OF A MATERNALLY EXPRESSED NOVEL XENOPUS GENE XEM1 ENCODING A PUTATIVE EVOLUTIONARILY CONSERVED MEMBRANE-PROTEIN

A novel Xenopus maternally expressed gene, Xem1, was isolated by diffe rential display PCR and 5'-RACE. Xem1 coded for a putative transmembra ne protein of 172 amino acids. Sequence analysis, including the cluste ring and reconstruction of ESTs (Expressed Sequence Tags), revealed th at homologs of Xem1 are widely distributed in eukaryotic phyla, sugges ting that Xem1 is a member of evolutionarily conserved proteins. Expre ssion of Xem1 mRNA occurred from the previtellogenic stage and its lev el increased during oogenesis, maintained throughout oocyte maturation to blastula stage and then decreased in post gastrula stages. In clea vage stage, Xem1 RNA was distributed uniformly, and in adult, occurred predominantly in ovary and testis. We assume that Xenopus Xem1 may ha ve its function in gametogenesis and ire early phase of embryogenesis, whose function may he related to transport mechanism of small molecul ar weight substances like metal ions, from analogy to the function of its homologs in other organisms. (C) 1997 Academic Press.