Adrift, a novel bnl-induced Drosophila gene, required for tracheal pathfinding into the CNS

Neurons and glial cells provide guidance cues for migrating neurons, We sho w here that migrating epithelial cells also contact specific neurons and gl ia during their pathfinding, and we describe the first gene required in the process. In wild-type Drosophila embryos, the ganglionic tracheal branch n avigates a remarkably complex path along specific neural and glial substrat a, switching substrata five times before reaching its ultimate target in th e CNS, In adrift mutants, ganglionic branches migrate normally along the in tersegmental nerve, but sporadically fail to switch to the segmental nerve and enter the CNS; they wind up meandering along the ventral epidermis inst ead. adrift encodes a novel nuclear protein with an evolutionarily conserve d motif. The gene is required in the trachea and is expressed in the leadin g cells of migrating ganglionic branches where it is induced by the branchl ess FGF pathway. We propose that Adrift regulates expression of tracheal ge nes required for pathfinding on the segmental nerve, and FGF induction of a drift expression in migrating tracheal cells promotes the switch from the i ntersegmental to the segmental nerve.