Members of the WNT signaling pathways are widely expressed in mouse ovaries, oocytes, and cleavage stage embryos.

The mammalian oocyte-to-embryo transition, characterized by a period of transcriptional silence, is dependent on maternal RNAs and proteins produced during the growth phase of the oocyte. Signaling pathways control timely transcription and translation of RNA, as well as post-translational modification of proteins. The WNT/beta-catenin pathway is clearly not active during preimplantation embryo development. However, alternative Wnt signaling pathways may play a role during early embryo development. This study describes the extensive expression, at the transcript and protein level, of receptors, ligands, and intracellular molecules known to play a role in WNT signaling, as well as those known to negatively regulate the canonical WNT/beta-catenin pathway in developing oocytes and preimplantation embryos. This expression of a wide array of molecules involved in WNT signaling suggests that the alternative WNT pathways may be active during oogenesis and the oocyte-to-embryo transition. (c) 2008 Wiley-Liss, Inc.