The Journal of Neuroscience, March 18, 2009, 29(11):3404-3418; doi:10.1523/JNEUROSCI.5464-08.2009
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Development/Plasticity/Repair
Reverse Signaling by Glycosylphosphatidylinositol-Linked Manduca Ephrin Requires a Src Family Kinase to Restrict Neuronal Migration In Vivo
Thomas M. Coate,
Tracy L. Swanson, and
Philip F. Copenhaver
Department of Cell and Developmental Biology, Oregon Health & Science University, Portland, Oregon 97239
Correspondence should be addressed to Dr. Philip F. Copenhaver, Department of Cell and Developmental Biology L-215, Oregon Health & Science University, 3181 Southwest Sam Jackson Park Road, Portland, OR 97239. Email: copenhav{at}ohsu.edu
Reverse signaling via glycosylphosphatidylinositol (GPI)-linked Ephrins may help control cell proliferation and outgrowth within the nervous system, but the mechanisms underlying this process remain poorly understood. In the embryonic enteric nervous system (ENS) of the moth Manduca sexta, migratory neurons forming the enteric plexus (EP cells) express a single Ephrin ligand (GPI-linked MsEphrin), whereas adjacent midline cells that are inhibitory to migration express the cognate receptor (MsEph). Knocking down MsEph receptor expression in cultured embryos with antisense morpholino oligonucleotides allowed the EP cells to cross the midline inappropriately, consistent with the model that reverse signaling via MsEphrin mediates a repulsive response in the ENS. Src family kinases have been implicated in reverse signaling by type-A Ephrins in other contexts, and MsEphrin colocalizes with activated forms of endogenous Src in the leading processes of the EP cells. Pharmacological inhibition of Src within the developing ENS induced aberrant midline crossovers, similar to the effect of blocking MsEphrin reverse signaling. Hyperstimulating MsEphrin reverse signaling with MsEph-Fc fusion proteins induced the rapid activation of endogenous Src specifically within the EP cells, as assayed by Western blots of single embryonic gut explants and by whole-mount immunostaining of cultured embryos. In longer cultures, treatment with MsEph-Fc caused a global inhibition of EP cell migration and outgrowth, an effect that was prevented by inhibiting Src activation. These results support the model that MsEphrin reverse signaling induces the Src-dependent retraction of EP cell processes away from the enteric midline, thereby helping to confine the neurons to their appropriate pathways.
Received Nov. 12, 2008;
revised Jan. 20, 2009;
accepted Jan. 26, 2009.
Correspondence should be addressed to Dr. Philip F. Copenhaver, Department of Cell and Developmental Biology L-215, Oregon Health & Science University, 3181 Southwest Sam Jackson Park Road, Portland, OR 97239. Email: copenhav{at}ohsu.edu