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

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