Novel zinc finger proteins that interact with the mouse γF-crystallin promoter and are expressed in the sclerotome during early somitogenesis

Lens-specific expression of the mouse γF-crystallin gene is determined, at least in part, by a 23-bp DNA element, the γF-1-binding motif, located in the promoter region of the gene. To characterize the transcription factors that regulate γF-crystallin gene expression through this element, we have isolated three chicken cDNAs that encode proteins capable of binding specifically to the γF-1-binding motif. These three cDNAs represent differential splicing products from a single gene, γFBP. The protein isoforms encoded by two of these cDNAs differ in their ability to modulate the activity of promoters containing the γF-1-binding motif. Among them, γFBP-B functions as a transcriptional repressor in lens cells, and it’s expression is developmentally regulated during lens development, suggesting a role for this isoform in the spatial regulation of γF-crystallin gene expression. We also show that expression of the different mRNA transcripts are differentially regulated in various tissues. Furthermore, γFBP transcripts are highly expressed in presomitic mesoderm and then over the entire epithelial somite. During somitic differentiation, γFBP expression becomes restricted to the sclerotome. These expression patterns suggest a regulatory role for the γFBP isoforms in sclerotome specification and/or differentiation.