Role of mouse maternal Cdx2: what's the debate all about?

Whether mouse oocytes are polarized and pre-patterned has been the subject of controversy for many years. Cdx2, a class I homeobox transcription factor of the caudal-related homeobox gene family, is involved in defining the anterior/posterior body axis, establishing anterior/posterior patterning of the intestine and forming a functional trophectoderm. The latter phenomenon suggests that maternal Cdx2 might be unevenly distributed in oocytes and plays a key role in the first lineage separation event in mouse preimplantation embryos. Unfortunately, two recent reports on the knockdown of maternal Cdx2 have produced contradictory results. As two authors of one of these reports, we would like to address these results and the corresponding commentary of Alexander W Bruce with this commentary.