A homeobox gene,pnx, is involved in the formation of posterior neurons in zebrafish

Abstract

A homeobox gene, pnx, is expressed in prospective posterior neurogenic regions and later in primary neurons. pnx expression was regulated by a signal from the non-axial mesendoderm and by Notch signaling. Pnx contains an Eh1 repressor domain, which interacted with Groucho and acted as a transcriptional repressor. Misexpression of pnx increased neural precursor cells and postmitotic neurons, which express neurogenin1and elavl3/HuC, respectively. Expression of an antimorphic Pnx(VP16Pnx) or inhibition of Pnx by antisense morpholino oligonucleotide led to the reduction in the number of a subset of primary neurons. Misexpression ofpnx promoted neurogenesis independent of Notch signaling. Epistatic analyses showed that Pnx also functions downstream of the Notch signal. These data indicate that pnx is a novel repressor-type homeobox gene that regulates posterior neurogenesis.