Hmgcr promotes a long-range signal to attract germ cells which is aided by Wunens but independent of hh

Abstract

Summary StatementMigrating Drosophila germ cells are attracted by a long range Hmgcr mediated signal which is aided and acts simultaneously with Wunens suggesting that these pathways converge on a single chemoattractant.\n\nAbstractIn a developing embryo, many cell types migrate from their point of specification to their final position. This usually involves highly stereotyped routes which are determined through deployment of cell surface or secreted guidance molecules. Whilst genetic techniques have been successful in identifying these molecules, the distances over which such signals operate in their native context can be difficult to determine. Here we have quantified the range of an attractive signal for the migration of Drosophila germ cells. Their migration is guided by an attractive signal generated by the expression of genes in the 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase (Hmgcr) pathway, and by a repulsive signal generated by the expression of Wunens. We demonstrate that the attractive signal downstream of Hmgcr operates over a long range and is sufficient to reach germ cells for the entirety of their migration. Furthermore, Hmgcr-mediated attraction and Wunen-mediated repulsion can operate simultaneously ruling out a model in which these pathways operate consecutively. Indeed, we show that Hmgcr-mediated attraction is boosted by Wunens suggesting the action of these two pathways is linked. Lastly, several papers have pointed to the secreted molecule Hedgehog (Hh) as being the germ cell attractant, whose secretion is increased by hmgcr. In this paper, we provide evidence that Hh is not downstream of hmgcr in germ cell migration.