Regulation of trunk neural crest delamination by δEF1 and Sip1 in the chicken embryo.

The vertebrate Zfhx1 transcription factor family comprises δEF1 and Sip1, which bind to CACCT-containing sequences and act as transcriptional repressors. It has been a longstanding question whether these transcription factors share the same regulatory functions in vivo. It has been shown that neural crest (NC) delamination depends on the Sip1 activity at the cranial level in mouse and chicken embryos, and it remained unclear how NC delamination is regulated at the trunk level. We observed that the expression of δEF1 and Sip1 overlaps in many tissues in chicken embryos, including NC cells at the trunk level. To clarify the above questions, we separately knocked down δEF1 and Sip1 or in combination in NC cells by electroporation of vectors expressing short hairpin RNAs (shRNAs) against respective mRNAs on the dorsal side of neural tubes that generate NC cells. In all cases, the migrating NC cell population was significantly reduced, paralleled by the decreased expression of δEF1 or Sip1 targeted by shRNAs. Expression of Sox10, the major transcription factor that regulates NC development, was also decreased by the shRNAs against δEF1 or Sip1. We conclude that the trunk NC delamination is regulated by both δEF1 and Sip1 in an analogous manner, and that these transcription factors can share equivalent regulatory functions in embryonic tissues.