Magnitude of binocular vision controlled by islet-2 repression of a genetic program that specifies laterality of retinal axon pathfinding.
Pathfinding of retinal ganglion cell (RGC) axons at the midline optic chiasm determines whether RGCs project to ipsilateral or contralateral brain visual centers, critical for binocular vision. Using Isl2tau-lacZ knockin mice, we show that the LIM-homeodomain transcription factor Isl2 marks only contralaterally projecting RGCs. The transcription factor Zic2 and guidance receptor EphB1, required by RGCs to project ipsilaterally, colocalize in RGCs distinct from Isl2 RGCs in the ventral-temporal crescent (VTC), the source of ipsilateral projections. Isl2 knockout mice have an increased ipsilateral projection originating from significantly more RGCs limited to the VTC. Isl2 knockouts also have increased Zic2 and EphB1 expression and significantly more Zic2 RGCs in the VTC. We conclude that Isl2 specifies RGC laterality by repressing an ipsilateral pathfinding program unique to VTC RGCs and involving Zic2 and EphB1. This genetic hierarchy controls binocular vision by regulating the magnitude and source of ipsilateral projections and reveals unique retinal domains.
Pak
Winnie
W
Molecular Neurobiology Lab, The Salk Institute, La Jolla, CA 92037, USA.
Hindges
Robert
R
Lim
Yoo-Shick
YS
Pfaff
Samuel L
SL
O'Leary
Dennis D M
DD
D000818:Animals; D001369:Axons / Q000502:physiology; D007839:Functional Laterality; D005786:Gene Expression Regulation; D018398:Homeodomain Proteins / Q000235:genetics / Q000502:physiology*; D060850:LIM-Homeodomain Proteins; D051379:Mice; D008817:Mice, Mutant Strains; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000502:physiology*; D036183:Receptor, EphB2 / Q000378:metabolism; D012160:Retina / Q000378:metabolism / Q000502:physiology*; D012165:Retinal Ganglion Cells / Q000502:physiology*; D014157:Transcription Factors / Q000378:metabolism; D015348:Vision, Binocular; D014795:Visual Pathways / Q000502:physiology
D018398:Homeodomain Proteins; C558561:Isl2 protein, mouse; D060850:LIM-Homeodomain Proteins; D009419:Nerve Tissue Proteins; D014157:Transcription Factors; C491811:Zic2 protein, mouse; C063843:insulin gene enhancer binding protein Isl-1; D036183:Receptor, EphB2