MAMMALIAN MALE AND FEMALE GERM-CELLS EXPRESS A GERM CELL-SPECIFIC Y-BOX PROTEIN, MSY2

Here we report the isolation and characterization of mouse testicular cDNAs encoding the mammalian homologue of the Xenopus germ cell-specif ic nucleic acid-binding protein FRGY2. (mRNP3+4), hereafter designated MSY2. MSY2. is a member of the Y box multigene family of proteins; it contains the cold shock domain that is highly conserved among all Y b ox proteins and four basic/aromatic islands that are closely related t o the other known germline Y box proteins from Xenopus, FRGY2, and gol dfish, GFYP2. Msy2 undergoes alternative splicing to yield alternate N -terminal regions upstream of the cold shock domain. Although MSY2 is a member of a large family of nucleic acid-binding proteins, Southern blotting detects only a limited number of genomic DNA fragments, sugge sting that Msy2 is a single copy gene. By Northern blotting and immuno blotting, MSY2 appears to be a germ cell-specific protein in the testi s. Analysis of Msy2 mRNA expression in prepubertal and adult mouse tes tes, and in isolated populations of germ cells, reveals maximal expres sion in postmeiotic round spermatids, a cell type with abundant amount s of stored messenger ribonucleoproteins. In the ovary, MSY2 is presen t exclusively in diplotene-stage and mature oocytes. MSY2 is maternall y inherited in the one-cell-stage embryo but is not detected in the la te two-cell-stage embryo. This loss of MSY2 is coincident with the bul k degradation of maternal mRNAs in the two-cell embryo.