Retinal axon growth at the optic chiasm: to cross or not to cross.
At the optic chiasm, retinal ganglion cell axons from each eye converge and segregate into crossed and uncrossed projections, a pattern critical for binocular vision. Here, we review recent findings on optic chiasm development, highlighting the specific transcription factors and guidance cues that implement retinal axon divergence into crossed and uncrossed pathways. Although mechanisms underlying the formation of the uncrossed projection have been identified, the means by which retinal axons are guided across the midline are still unclear. In addition to directives provided by transcription factors and receptors in the retina, gene expression in the ventral diencephalon influences chiasm formation. Throughout this review, we compare guidance mechanisms at the optic chiasm with those in other midline models and highlight unanswered questions both for retinal axon growth and axon guidance in general.
Department of Pathology and Cell Biology, Department of Neuroscience, Columbia University, College of Physicians and Surgeons, New York, New York 10032, USA. tjp2001@columbia.edu
Timothy J
TJ
Petros
Alexandra
A
Rebsam
Carol A
CA
Mason
D000818:Animals; D001921:Brain / Q000196:embryology* / Q000502:physiology; D007839:Functional Laterality / Q000235:genetics; D018507:Gene Expression Regulation, Developmental / Q000235:genetics; D020439:Growth Cones / Q000502:physiology / Q000648:ultrastructure*; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D009897:Optic Chiasm / Q000196:embryology* / Q000502:physiology; D012160:Retina / Q000196:embryology* / Q000502:physiology; D012165:Retinal Ganglion Cells / Q000166:cytology* / Q000502:physiology; D015348:Vision, Binocular / Q000502:physiology*; D014795:Visual Pathways / Q000196:embryology / Q000502:physiology
D036341:Intercellular Signaling Peptides and Proteins