Maternal determinants of embryonic cell fate.

How important is the contribution of mRNAs and proteins stored in the oocyte for determining the body plan of the Xenopus embryo? Here we review the current understanding of the roles of maternally supplied transcription factors, signaling molecules, and signaling regulators in establishing the ectoderm, mesoderm, and endoderm germ layers and the embryonic axes. Key essential asymmetries of VegT, Wnt11, and Ectodermin are described, as well as the complexity of maternal transcription factors that are involved in the initial expression of early zygotic genes.