Oogenic function of the myogenic factor D-MEF2: Negative regulation of theDecapentaplegic receptor gene thick veins

The myogenic factor D-MEF2 is required for the proper differentiation of mu scle cells during Drosophila embryogenesis and the correct patterning of in direct flight muscles assembled during later metamorphosis. In addition to these essential myogenic functions, mutant D-mef2 adult females are weakly fertile and produce defective eggs. D-MEF2 is expressed in nurse and follic le cells of the wild-type egg chamber. We have analyzed the D-mef2 oogenic phenotype and show that the gene is required for the normal patterning and differentiation of the centripetally migrating follicle cells that are cruc ial for development of the anterior chorionic structures. D-mef2 alleles ex hibit a genetic interaction with a dominant-negative allele of thick veins (tkv), which encodes a type I receptor of the Decapentaplegic-signaling pat hway. tkv RNA is overexpressed in D-mef2 mutant egg chambers, and, converse ly, forced expression of D-mef2 represses tkv expression. These results ind icate a role for D-MEF2 in the regulation of tkv gene expression and Decape ntaplegic signal transduction that are essential for proper determination a nd/or differentiation of the anterior follicle cells. Additionally, they de monstrate a vital function for the D-MEF2 transcription factor in multiple genetic pathways during Drosophila development.