Transcriptional profiling of Wnt3a mutants identifies Sp transcription factors as essential effectors of the Wnt/β-catenin pathway in neuromesodermal stem cells.

Neuromesodermal (NM) stem cells reside in the primitive streak (PS) of gastrulating vertebrate embryos and generate precursors of the spinal cord and musculoskeletal system. Although Wnt3a/β-catenin signaling is crucial for NM stem cell maintenance and differentiation, few key transcriptional effectors have been identified. Through a concerted transcriptional profiling and genetic approach we have determined that two Zn(2+)-finger transcription factors, Sp5 and Sp8, are regulated by Wnt3a in the PS, and are essential for neural and musculoskeletal patterning.

Xrel3/XrelA attenuates β-catenin-mediated transcription during mesoderm formation in Xenopus embryos.

In Xenopus laevis embryonic development, activation of the Wnt/β-catenin pathway promotes mesoderm cell fate determination via Xnr (Xenopus nodal-related) expression. We have demonstrated previously that Rel/NF-κB (nuclear factor κB) proteins expressed in presumptive ectoderm limit the activity of Xnrs to the marginal zone of embryos during mesoderm induction, which assists to distinguish mesoderm from ectoderm. The mechanism of this regulation, however, is unknown.