Blood vessel/epicardial substance (bves) expression, essential for embryonic development, is down regulated by Grk/EFGR signalling.

The Pop1/Bves (blood vessel/epicardial substance) gene is a member of the popeye gene family recently identified in various species. It encodes a potential transmembrane glycoprotein and is a cell adhesion molecule present in skeletal and cardiac muscle and epithelia. We isolated the Drosophila homologue of Bves (DmBves) and found, using in situ hybridisation to RNA in ovaries, that bves is expressed in all follicular epithelial cells surrounding the oocyte at stage 10, except those in very posterior and anterior-dorsal regions adjacent to the oocyte. We show that the repression of bves expression in anterior-dorsal follicle cells is regulated by the Grk/EGFR signalling pathway. Bves is also expressed in nurse cells during oogenesis and its transcripts are then translocated into the oocyte. Expression of bves antisense RNA during oogenesis causes reduced viability in the resulting embryos. There is a failure in the migration of pole cells from the posterior towards the antero-dorsal side of the embryo, probably resulting from abnormal germband extension and we suggest that bves is essential for normal embryonic development.