Oocytes and early embryos selectively express the survival factor BCL2L10

Apoptosis has been reported in oocytes and human preimplantation embryos both in vitro and in vivo. BCL-2 family proteins are likely to play a pivotal role in controlling oocyte and early embryo degeneration. However, no BCL-2-related survival factors have been identified that would specifically function during oocyte maturation, after fertilization and during early embryogenesis. Here, we performed a comprehensive tissue expression pattern analysis of the BCL-2 family at the mRNA level. While expression of various members was detected in human oocytes and during early primate embryogenesis, our data indicate that BCL2L10 is the predominant maternally loaded Bcl-2 family transcript, revealing an evolutionary conserved expression profile at the egg-to-zygote transition. We provide evidence that BCL2L10 is associated with the microtubule binding protein translationally controlled tumor protein and mitochondria, with a stage-specific redistribution along the pericortical regulatory ooplasm. In dying oocytes, BCL2L10 colocalized with proapoptotic BAX and neutralization of BCL2L10 accelerated oocyte death. We propose BCL2L10 as a novel and prime candidate related to oocyte maturation, fertility, and embryo developmental competence.