HGF-SF: a neural inducing molecule in vertebrate embryos?

Neural induction is the process, during early embryonic development, by which cells of the mesoderm cause the overlying ectoderm cells to differentiate into neural structures, rather than epidermis. The phenomenon was discovered over 80 years ago in Hans Spemann's laboratory, and has since attracted much interest. However, we are still ignorant about the signals that elicit such a change in the direction of ectodermal differentiation, and about the mechanisms involved in the response of the ectoderm. Here, we report that HGF-SF can cause cultured chick ectodermal cells to become neural. We also discuss preliminary evidence suggesting that a homolog of this factor is expressed in Hensen's node, the inducing tissue, at about the stage at which neural induction occurs. We speculate that HGF-SF, or a related factor, could be a neural inducing signal during the early development of vertebrate embryos.