[Abstract Title]. - Society for Neuroscience

Poster
230. Cell Migration: Molecules Mediating Migration
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 230.16/B6
Topic: A.02.c. Cell migration
Support: NIH Grant AG25525
NIH Grant T32 HD049309
Title: Local activation of a Src family kinase mediates reverse signaling via a specific GPIlinked
Ephrin within migrating neurons during embryonic development
Authors: *P. F. COPENHAVER 1 , T. L. SWANSON 2 , T. M. COATE 2 ;
1 Dept Cell & Dev Biol, 2 Cell & Developmental Biol., Oregon Hlth. & Sci. Univ., Portland, OR
Abstract: Bidirectional signaling by Eph receptors and their Ephrin ligands regulates many
aspects of neuronal development, but the mechanisms by which GPI-linked (type A) ephrins
mediate reverse signaling are poorly understood. Using a model systems approach, we have
shown that reverse signaling via a specific GPI-linked Ephrin regulates the guidance of
migrating neurons within the developing enteric nervous system (ENS) of the hornworm
Manduca sexta. During the formation of the ENS, a population of ~300 neurons (EP cells) must
migrate selectively along pre-formed muscle bands on the gut surface, while avoiding adjacent
midline regions. Notably, the migrating EP cells express the sole Ephrin ligand in Manduca
(MsEphrin, a GPI-linked ligand), whereas the midline muscle cells express the cognate Eph
receptor (MsEph). Manipulations in cultured embryos verified that reverse signaling via
MsEphrin prevents the EP cells from crossing the enteric midline, while forward signaling via
MsEph receptors is not required. Recently, we discovered that MsEphrin reverse signaling is
mediated by a Src family kinase (MsSrc). Hyperactivating MsEphrin reverse signaling (with
MsEph-Fc) caused a dramatic increase in MsSrc activity in the EP cells and inhibited their
motility, as demonstrated by quantitative confocal analyses and biochemical assays of the ENS
from single embryos. In contrast, inhibiting endogenous MsSrc activity blocked reverse
signaling and induced the same midline crossover phenotypes caused by blocking endogenous
MsEphrin-MsEph interactions. These results indicate that endogenous MsSrc is necessary for the
transmission of MsEphrin reverse signals in the migrating neurons. We have cloned both Src
family kinases that are expressed in Manduca (MsSrc42 and MsSrc64), and we are currently
testing whether one or both of these Src orthologues mediates MsEphrin reverse signaling. Using
similar methods, we found that MsEphrin-dependent Src stimulation leads to the local activation
of Rho GTPase in the EP cells, which in turn is required for their retraction/repulsion away from