Retinal axon guidance by region-specific cues in diencephalon.
Retinal axons show region-specific patterning along the dorsal-ventral axis of diencephalon: retinal axons grow in a compact bundle over hypothalamus, dramatically splay out over thalamus, and circumvent epithalamus as they continue toward the dorsal midbrain. In vitro, retinal axons are repulsed by substrate-bound and soluble activities in hypothalamus and epithalamus, but invade thalamus. The repulsion is mimicked by a soluble floor plate activity. Tenascin and neurocan, extracellular matrix molecules that inhibit retinal axon growth in vitro, are enriched in hypothalamus and epithalamus. Within thalamus, a stimulatory activity is specifically upregulated in target nuclei at the time that retinal axons invade them. These findings suggest that region-specific, axon repulsive and stimulatory activities control retinal axon patterning in the embryonic diencephalon.
Tuttle
R
R
Molecular Neurobiology Laboratory, The Salk Institute, La Jolla, CA 92037, USA.
Braisted
J E
JE
Richards
L J
LJ
O'Leary
D D
DD
D000818:Animals; D001369:Axons / Q000502:physiology / Q000648:ultrastructure*; D002450:Cell Communication; D002467:Cell Nucleus / Q000502:physiology; D002642:Chick Embryo; D011508:Chondroitin Sulfate Proteoglycans / Q000502:physiology; D004027:Diencephalon / Q000196:embryology* / Q000502:physiology; D005260:Female; D005829:Geniculate Bodies / Q000196:embryology; D007031:Hypothalamus / Q000196:embryology; D037181:Lectins, C-Type; D051379:Mice; D008810:Mice, Inbred C57BL; D009419:Nerve Tissue Proteins / Q000502:physiology; D058580:Neurocan; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley; D012160:Retina / Q000196:embryology* / Q000502:physiology / Q000648:ultrastructure*; D012165:Retinal Ganglion Cells / Q000502:physiology / Q000648:ultrastructure*; D019063:Tenascin / Q000502:physiology; D013788:Thalamus / Q000196:embryology; D014795:Visual Pathways / Q000196:embryology / Q000648:ultrastructure
D011508:Chondroitin Sulfate Proteoglycans; D037181:Lectins, C-Type; D009419:Nerve Tissue Proteins; D058580:Neurocan; D019063:Tenascin; C076817:NCAN protein, human