Transcripts of Grg4, a murine groucho-related gene, are detected in adjacent tissues to other murine neurogenic gene homologues during embryonic development

The groucho-related genes (Grg) of the mouse comprise at least four family members. In Drosophila, groucho is one of the neurogenic genes that participates in the Notch signalling pathway. The Groucho protein interacts with Hairy-related transcription factors to regulate segmentation, neurogenesis and sex determination. Thus, by analogy to the Drosophila proteins, murine Grg proteins may interact with mammalian Hairy and E(spl) homologues (Hes proteins) and take part in a signalling pathway downstream of murine Notch. We have isolated murine Grg4 cDNAs and examined Grg4 expression during embryogenesis. Transcripts of Grg4 were detected in proliferating epithelial tissues undergoing mesenchymal induction, overlapping with Grg3, Notch1 and Hes1 expression. Grg4 was also expressed in the central nervous system and somites, but in cells adjacent to Grg3-, Notch1-, and Hes1-expressing cells. This distinct pattern of expression suggests a role for Grg4 in later stages of cell differentiation than for the other mouse neurogenic gene homologues.