Topographic mapping from the retina to the midbrain is controlled by relative but not absolute levels of EphA receptor signaling.
Topographic maps are a fundamental feature of sensory representations in nervous systems. The formation of one such map, defined by the connection of ganglion cells in the retina to their targets in the superior colliculus of the midbrain, is thought to depend upon an interaction between complementary gradients of retinal EphA receptors and collicular ephrin-A ligands. We have tested this hypothesis by using gene targeting to elevate EphA receptor expression in a subset of mouse ganglion cells, thereby producing two intermingled ganglion cell populations that express distinct EphA receptor gradients. We find that these two populations form separate maps in the colliculus, which can be predicted as a function of the net EphA receptor level that a given ganglion cell expresses relative to its neighbors.
Molecular Neurobiology Laboratory, The Salk Institute, La Jolla, California 92037, USA.
A
A
Brown
P A
PA
Yates
P
P
Burrola
D
D
Ortuño
A
A
Vaidya
T M
TM
Jessell
S L
SL
Pfaff
D D
DD
O'Leary
G
G
Lemke
D000818:Animals; D001369:Axons / Q000378:metabolism / Q000502:physiology; D001931:Brain Mapping / Q000379:methods; D005136:Eye Proteins / Q000235:genetics / Q000502:physiology; D015870:Gene Expression; D018390:Gene Targeting; D018398:Homeodomain Proteins / Q000235:genetics / Q000502:physiology; D060850:LIM-Homeodomain Proteins; D008636:Mesencephalon / Q000502:physiology*; D051379:Mice; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000502:physiology; D009434:Neural Pathways; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics / Q000502:physiology*; D036121:Receptor, EphA3; D036123:Receptor, EphA5; D012160:Retina / Q000378:metabolism / Q000502:physiology*; D012165:Retinal Ganglion Cells / Q000378:metabolism / Q000502:physiology; D015398:Signal Transduction; D014157:Transcription Factors
D005136:Eye Proteins; D018398:Homeodomain Proteins; D060850:LIM-Homeodomain Proteins; D009419:Nerve Tissue Proteins; D014157:Transcription Factors; C063843:insulin gene enhancer binding protein Isl-1; C491717:Epha3 protein, mouse; D020794:Receptor Protein-Tyrosine Kinases; D036121:Receptor, EphA3; D036123:Receptor, EphA5