Spindlin, a major maternal transcript expressed in the mouse during the transition from oocyte to embryo

Timely translation of maternal transcripts and post-translational modification of their gene products control the initial development of preimplantation-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 unfertilized egg and 2-cell, but not 8-cell, stage embryo. Spin exhibits high homology to a multicopy gene, Y-linked spermiogenesis-specific transcript (Ssty), and together they form a new gene family expressed during gametogenesis. 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 30 x 10³ M(r) metaphase complex which is post-translationally modified during the first mitotic cell cycle. Our data suggest that spindlin plays a role in cell-cycle regulation during the transition from gamete to embryo.