Tumorhead, a Xenopus gene product that inhibits neural differentiation through regulation of proliferation

Tumorhead (TH) is a novel maternal gene product from Xenopus laevis contain ing several basic domains and a weak coiled-coil. Overexpression of wild-ty pe TH resulted in increased proliferation of neural plate cells, causing ex pansion of the neural field followed by neural tube and craniofacial abnorm alities. Overexpressed TH protein repressed neural differentiation and neur al crest markers, but did not inhibit the neural inducers, pan-neural marke rs or mesodermal markers. Loss of function by injection of anti-TH antibody inhibited cell proliferation. Our data are consistent with a model in whic h tumorhead functions in regulating differentiation of the neural tissues b ut not neural induction or determination through its effect on cell prolife ration.