Fig. 7. Analysis of xTAB3 involvement in BMP signaling and neural induction. (A) Dendrogram of the identified TAB2 and TAB3 family. Murine and human TAB3 were found in NCBI searches. Two TAB-related genes found in the fugu database are included (JGI 18320 and JGI 564). (B) Schematic of xTAB3 and xTAB3C proteins. Yellow box depicts the CUE domain (ubiquitin ligase interacting domain). Green box depicts the Zn-finger motif. (C) Injection of xTAB3C RNA into animal caps results in upregulation of epidermal keratin expression in gastrula stage explants, a marker responsive to BMP signaling. There is no mesodermal gene expression in these caps (xBra). (D-G) Animal cap explants (stage 23) injected with 50 pg Smad7 form neural and cement gland tissue (E). Notice pigmented cement glands (arrowheads). Co-expression with xTAB3C largely inhibits cement gland (F). (H) Analysis of explants injected with 50 pg of Smad7 or noggin in the absence (lanes 3, 6) or presence (lanes 4, 8) of xTAB3C shows that xTAB3C can inhibit neural and cement gland fates induced by BMP inhibitors.