During nervous system development, axons are guided by many attractive and repulsive cues. For example, members of the RYK/Derailed family of inactive receptor tyrosine kinases guide axons in the Drosophila ventral nerve cord and in the mammalian brain by acting as Wnt receptors. On , Wouda et al. reveal how these kinase-inactive RYKs might transduce Wnt signals by reporting that WNT5-mediated signalling through Derailed in the Drosophilaembryonic CNS involves the non-receptor Src family tyrosine kinases SRC64B and SRC42A. Src64B/Src42A double mutants, they show, have defects in the formation of the nerve fibre tracts that connect the two sides of the brain(commissures) similar to those seen in Wnt5 and derailedmutants. Derailed and SRC64B, they report, form a complex, the formation and/or stability of which requires SRC64B activity. Furthermore, the mammalian orthologues of these proteins also form complexes together. Thus, Src family kinases might play novel roles in Wnt5/Derailed signalling during CNS development in flies and in mammals.
