Xenopus Zic4: conservation and diversification of expression profiles and protein function among the Xenopus Zic family.

We compared the expression and function of Xenopus Zic4 with those of the other four Xenopus laevis Zic family members (Zic1, Zic2, Zic3, and Zic5). Zic4 expression was detected mainly in the neural plate border, dorsal neural tube, and somites, and was similar to that of Zic1, which is adjacent to Zic4 on the same chromosome. Injection of wild-type or mutant Zic4 RNA caused the induction of neural crest marker gene expression, hyperplastic neural tissue, and ectopic pigment cell formation, indicating that Zic4 can induce neural and neural crest tissue, as can other Xenopus Zic genes. Deletion analysis showed that the zinc-finger domain is critical for many Zic4 functions, but the C-terminal region is differently involved in induction of two neural crest markers, Slug and Sox10. The protein function as determined by the animal cap explant assay was similar to that of Zic5, but different from those of Zic1, Zic2, and Zic3, suggesting that Xenopus Zic genes can be divided into two groups based on function. These results indicate that the five Xenopus Zic genes cooperatively regulate both neural and neural crest development, despite significantly diverged expression profiles and functions. Copyright (c) 2006 Wiley-Liss, Inc.