The proto-oncogene src encodes a protein tyrosine kinase involved in cell signaling pathways that control growth, development, and differentiation in metazoans. We are using C. elegans to understand the function and evolution of src. The worm genome contains two src genes:
src-1 (Y92H12A.1) located on the left arm of LGI and
src-2 (F49B2.5) located on the right arm of LGI. Previously, in collaboration with the Mello lab, we reported that a
src-1 knockout confers a maternal effect lethal phenotype. Arrested embryos exhibit distinct abnormalities suggesting
src-1 plays an essential role in cell fate decisions and morphogenesis in the early embryo, acting in parallel with the Wnt pathway to mediate P2 to EMS signaling. However, both the
src-2 knockout strain (RB936) obtained from the C. elegans knock-out consortium and
src-2 RNAi nematodes appear wild type in all respects. This suggests that
src-1 plays an essential and unique role in the germline, whereas,
src-1 and
src-2 have redundant zygotic functions. Consistent with this model, in-situ data reveals that only
src-1 is expressed in the germline, in the meiotic region of the gonad. Real-time PCR and GFP data show that expression of both genes is widespread in the soma (especially in the sensory neurons, muscle, canal cell, and intestine) in all larval stages and adults. Expression of
src-1 is significantly higher than
src-2 in all stages. We are also taking a novel approach to identify targets of src phosphorylation, combining immunoprecipitation using a phosphotyrosine antibody with phosphopeptide analysis via mass spectrometry. Finally, to understand the evolution of these two highly conserved proteins, we performed a phylogenetic analysis of src family kinases gathered from a wide range of metazoans. The tree shows three clades, one of which consists solely of src kinases from C. elegans and D. melanogaster. This indicates that
src-1 and
src-2 are orthologous to Dsrc64 and Dsrc41, respectively, and provides evidence for an evolutionary link between nematodes and arthropods.