AL-1-induced growth cone collapse of rat cortical neurons is correlated with REK7 expression and rearrangement of the actin cytoskeleton.
Previous experiments identified AL-1 as a glycosylphosphatidylinositol (GPI)-linked ligand for the Eph-related receptor, REK7, and showed that a REK7-IgG fusion protein blocks axon bundling in co-cultures of cortical neurons on astrocytes, suggesting a role for REK7 and AL-1 in axon fasciculation. Subsequent identification of RAGS, the chick homologue of AL-1, as a repellent axon guidance molecule in the developing chick visual system led to speculation that AL-1, expressed on astrocytes, provides a repellent stimulus for cortical axons, inducing them to bundle as an avoidance mechanism. Using a growth cone collapse assay to test this hypothesis, we show that a soluble AL-1-IgG fusion protein is a potent collapsing factor for embryonic rat cortical neurons. The response is strongly correlated with REK7 expression, implicating REK7 as a receptor mediating AL-1-induced collapse. Morphological collapse is preceded by an AL-1-IgG-induced reorganization of the actin cytoskeleton that resembles the effects of cytochalasin D. This suggests a pathway whereby REK7 activation by AL-1 leads to perturbation of the actin cytoskeleton, possibly by an effect on actin polymerization, followed by growth cone collapse. We further show that AL-1-IgG causes collapse of rat hippocampal neurons and rat retinal ganglion cells. These data suggest a role for REK7 and AL-1 in the patterning of axonal connections in the developing cortex, hippocampus and visual system.
Meima
L
L
Department of Neuroscience, Genentech, Inc., South San Francisco, CA 94080, USA.
Kljavin
I J
IJ
Moran
P
P
Shih
A
A
Winslow
J W
JW
Caras
I W
IW
D000199:Actins / Q000096:biosynthesis*; D000818:Animals; D015704:CD4 Antigens / Q000378:metabolism; D002540:Cerebral Cortex / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism*; D036383:Ephrin-A2; D019084:Fluorescent Antibody Technique, Indirect; D017261:Glycosylphosphatidylinositols / Q000494:pharmacology; D006651:Histocytochemistry; D008024:Ligands; D009474:Neurons / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology*; D051381:Rats; D020794:Receptor Protein-Tyrosine Kinases / Q000096:biosynthesis* / Q000235:genetics; D012160:Retina / Q000166:cytology; D012235:Rhodamines; D014157:Transcription Factors / Q000494:pharmacology*; D014793:Visual Cortex / Q000166:cytology / Q000254:growth & development
D000199:Actins; D015704:CD4 Antigens; D036383:Ephrin-A2; D017261:Glycosylphosphatidylinositols; D008024:Ligands; D012235:Rhodamines; D014157:Transcription Factors; D020794:Receptor Protein-Tyrosine Kinases