Embryonic spatio-temporal expression pattern of Folded gastrulation (Fog) suggests roles in multiple morphogenetic events and regulation by AbdA.

In Drosophila, the signaling pathway activated by the ligand Folded gastrulation (Fog) is amongst the few known G-protein coupled receptor (GPCR) pathways to regulate cell shape change with a well characterized role in gastrulation. However, an understanding of the spectrum of morphogenetic events regulated by Fog signaling is still lacking. Here, we present an analysis of the expression pattern and regulation of fog using a genome engineered Fog::sfGFP line. We show that Fog expression is widespread and in tissues previously not associated with the signaling pathway including germ cells, trachea and amnioserosa. In the CNS, we find that the ligand is expressed in multiple types of glia indicating a prominent role in the development of these cells. Consistent with this, we have identified three intronic enhancers whose expression in the CNS overlaps with Fog::sfGFP. Further, we show that enhancer-1, (fog intenh-1) located proximal to the coding exon is responsive to AbdA. Supporting this, we find that fog expression is downregulated in abdA mutants. Together, our study highlights the broad scope of Fog-GPCR signaling during embryogenesis and identifies Hox gene AbdA as a novel regulator of fog expression.