Opposing gradients of ephrin-As and EphA7 in the superior colliculus are essential for topographic mapping in the mammalian visual system.
During development of the retinocollicular projection in mouse, retinal axons initially overshoot their future termination zones (TZs) in the superior colliculus (SC). The formation of TZs is initiated by interstitial branching at topographically appropriate positions. Ephrin-As are expressed in a decreasing posterior-to-anterior gradient in the SC, and they suppress branching posterior to future TZs. Here we investigate the role of an EphA7 gradient in the SC, which has the reverse orientation to the ephrin-A gradient. We find that in EphA7 mutant mice the retinocollicular map is disrupted, with nasal and temporal axons forming additional or extended TZs, respectively. In vitro, retinal axons are repelled from growing on EphA7-containing stripes. Our data support the idea that EphA7 is involved in suppressing branching anterior to future TZs. These findings suggest that opposing ephrin-A and EphA gradients are required for the proper development of the retinocollicular projection.
MRC Centre for Developmental Neurobiology, King's College London, New Hunt's House, Guy's Hospital Campus, London SE1 1UL, United Kingdom.
Tahira
T
Rashid
A Louise
AL
Upton
Aida
A
Blentic
Thomas
T
Ciossek
Bernd
B
Knöll
Ian D
ID
Thompson
Uwe
U
Drescher
D000818:Animals; D001369:Axons / Q000502:physiology; D001931:Brain Mapping; D036342:Ephrins / Q000378:metabolism*; D006651:Histocytochemistry; D017403:In Situ Hybridization; D051379:Mice; D018345:Mice, Knockout; D012313:RNA / Q000096:biosynthesis / Q000235:genetics; D036141:Receptor, EphA7 / Q000378:metabolism*; D012160:Retina / Q000166:cytology; D013477:Superior Colliculi / Q000378:metabolism* / Q000502:physiology*; D014785:Vision, Ocular / Q000502:physiology*; D014795:Visual Pathways / Q000502:physiology*
D036342:Ephrins; D012313:RNA; D036141:Receptor, EphA7