Xenopus Suppressor of Hairless 2 is involved in the cell fate decision during gastrulation through the transcriptional regulation of Xoct25/91

We have previously indicated that Xenopus Suppressor of Hairless 2, XSu(H)2, is involved in the morphogenesis of gastrula embryos in a different manner from the XESR-1-mediated Notch signaling pathway. To address the downstream factors of XSu(H)2, we investigated the effect of XSu(H)2 on XenopusPOU-V genes, Xoct25 and Xoct91. Knockdown of XSu(H)2 caused the downregulation of Xoct25, Xoct91 and Xbrachyury. Dominant-negative Xoct25 caused the delay of blastopore closure with a decrease of Xbrachyury expression. Overexpression of Xoct25 or Xoct91 could rescue the decrease of Xbrachyury expression caused by XSu(H)2 depletion. XSu(H)2EnR inhibited Xoct25 and Xoct91 expressions in CHX-treated animal caps. Promoter analysis of the Xoct25 showed that the upstream region of Xoct25 contains the prospective Su(H) binding motif, which is essential for the transcription of Xoct25. These results suggest that XSu(H)2 is engaged in the cell fate decision during gastrulation through the gene expression of the Xoct25/91-mediated pathway.