[Abstract Title]. - Society for Neuroscience

interneurons be fated to die, it also raises the intriguing question of how this fleeting subpopulation
contributes to cortical development and function.
Disclosures: D. Southwell , None; A. Alvarez-Buylla, None.
Poster
232. Developmental Cell Death: Biological Effects
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 232.21/B61
Topic: A.06.a. Developmental cell death: Biological effects
Title: The mechanism of neogenin-induced apoptosis
Authors: *Y. FUJITA 1 , J. TANIGUCHI 2 , M. UCHIKAWA 3 , M. ENDO 1 , K. HATA 1 , T.
YAMASHITA 1,2 ;
1 Dept Mol Neurosci, Grad Sch. Med, Osaka Univ., Osaka, Japan; 2 Dept Neurobiol, Grad Sch.
Med, Chiba Univ., Chiba, Japan; 3 Dept Dev Biol, Grad Sch. of Frontier Biosci, Osaka, Japan
Abstract: The repulsive guidance molecule (RGM) is a glycosylphosphatidylinositol (GPI)anchored
protein that shares no sequence homology with any other known proteins. And it was
originally identified in the chick retinotectal system. RGM repels retinal axons in the optic
tectum and induces the collapse of temporal but not nasal growth cones. Thus, it was thought that
it might be involved in topographic map formation. Recently, neogenin was identified as an
RGM receptor. In the ligand-free state, neogenin induces apoptosis. Neogenin overexpression or
RGMa down-regulation by small interference RNA (siRNA) in the developing neural tube of
chick embryos resulted induces apoptosis. However, the signal transduction mechanism that
induces cell death is completely unknown and remains to be analyzed.
In this study, we identified the serine/threonine kinase death associated protein kinase (DAPkinase)
to be an interactor of neogenin. DAP-kinase is a crucial intracellular protein that
mediates cell death via its serine threonine kinase activity. Here we show that DAP-kinase is
required for the proapoptotic activity of neogenin in vitro and in vivo. In HEK 293T cells,
neogenin enhances the activity of DAP-kinase in the absence of RGM but not in the presence of
RGM. To examine whether DAP-kinase is involved in neogenin-mediated cell death in vivo, we
analyzed cell death in neural tubes of chick embryos. We electroporated the control or neogenin
expression vectors with or without dominant negative form of DAP-kinase (DAPK-d/n) with the
GFP-expression vector in HH stage 10 chick embryos. In the neogenin electroporated side, there
was an increase in the number of TUNEL-positive cell wheareas, in the neogenin and DAPkinase
co-electroporated side, resulted in the disappearance of the TUNEL-positive cells.
Furthermore, we examined RGM functions as a cell survival factor to counteract neogenin