Expression of two insm1-like genes in the developing zebrafish nervous system.

Insulinoma associated-1 (INSM1, formerly IA-1) is a Cys(2)-His(2) zinc finger transcription factor sharing conserved regions with Caenorhabditis elegans EGL-46 and Drosophila Nerfin-1. INSM, EGL-46, and Nerfin proteins comprise the EIN family of zinc finger transcription factors. egl-46 and nerfin-1 have been implicated in various aspects of neuronal differentiation including cell fate specification, axon guidance decisions and cell migration. Murine Insm1 has a restricted expression pattern in the developing CNS. We have characterized two zebrafish (Danio rerio) Insm1-like genes, insm1a and insm1b, and analyzed their expression patterns during embryonic development. Zebrafish insm1a and insm1b share an embryonic expression pattern comparable to the proneural deltaA as well as overlapping the neuronal marker elavl3. The expression pattern observed for zebrafish insm1a and insm1b is similar to other EIN homologues. Both zebrafish insm1-like transcripts are also present in a region of the embryo where pancreatic progenitors originate. The expression data along with functional characterization of invertebrate homologues suggest a conserved pathway involving the EIN transcription factors in early neurogenesis.