SPINDLIN, A MAJOR MATERNAL TRANSCRIPT EXPRESSED IN THE MOUSE DURING THE TRANSITION FROM OOCYTE TO EMBRYO

Timely translation of maternal transcripts and post-translational modi fication of their gene products control the initial development of pre implantation-stage embryos. We have isolated and characterized a gene encoding a stage-specific embryonic protein, This novel gene, spindlin (Spin), is an abundant maternal transcript present in the unfertilize d egg and 2-cell, but not 8-cell, stage embryo, Spin exhibits high hom ology to a multicopy gene, Y-linked spermiogenesis-specific transcript (Ssty), and together they form a new gene family expressed during gam etogenesis, We find that spindlin associates with the meiotic spindle and is modified by phosphorylation in a cell-cycle-dependent fashion. Furthermore, it comigrates with the previously described 30x10(3) M(r) metaphase complex which is post-translationally modified during the f irst mitotic cell cycle. Our data suggest that spindlin plays a role i n cell-cycle regulation during the transition from gamete to embryo.