The Drosophila VEGF receptor homolog is expressed in hemocytes

Several signalling pathways have been defined by studies of genes originall y characterised in Drosophila. However, some mammalian signalling systems h ave so far escaped discovery in the fly. Here, we describe the identificati on and characterisation of fly homologs for the mammalian vascular endothel ial growth factor/platelet derived growth factor (VEGF/PDGF) and the VEGF r eceptor. The Drosophila factor (DmVEGF-1) gene has two splice variants and is expressed during all stages, the signal distribution during embryogenesi s being ubiquitous. The receptor (DmVEGFR) gene has several splice variants ; the variations affecting only the extracellular domain. The most prominen t form is expressed in cells of the embryonic haematopoietic cell lineage. starting in the mesodermal area of the head around stage 10 of embryogenesi s. Expression persists in hemocytes as embryonic development proceeds and t he cells migrate posteriorly. In a fly strain carrying a deletion uncoverin g the DmVEGFR gene, hemocytes are still present, but their migration is ham pered and the hemocytes remain mainly in the anterior end close to their or igin. These data suggest that the VEGF/PDGF signalling system may regulate the migration of the Drosophila embryonic haemocyte precursor cells. (C) 20 01 Elsevier Science Ireland Ltd. All rights reserved.