Wnt5a induces simultaneous cortical axon outgrowth and repulsive axon guidance through distinct signaling mechanisms.
Wnts are morphogens that also function as axon guidance molecules. In vivo Wnt5a gradients via Ryk receptors were found to repel cortical axons into developing callosal and corticospinal pathways. Here, using dissociated cortical cultures, we found that bath-applied Wnt5a increased axon outgrowth. In turning assays, Wnt5a gradients simultaneously increased axon outgrowth and induced repulsive turning, a potential mechanism for propelling cortical axons in vivo. We found that axon outgrowth is mediated by Ryk, whereas axon repulsion requires both Ryk and Frizzled receptors. Both receptors mediate Wnt-evoked fluctuations in intracellular calcium, which is required for increased axon outgrowth and repulsion by Wnt5a. However, whereas increased axon outgrowth involves calcium release from stores through IP3 receptors as well as calcium influx through TRP channels, axon repulsion is mediated by TRP channels without involvement of IP3 receptors. These results reveal distinct signaling mechanisms underlying Wnt5a-induced axon outgrowth and repulsive guidance.
Li
Li
L
Neuroscience Training Program, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
Hutchins
B Ian
BI
Kalil
Katherine
K
D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D001369:Axons / Q000187:drug effects* / Q000502:physiology; D001896:Boron Compounds / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D002465:Cell Movement / Q000187:drug effects; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology*; D006224:Cricetinae; D004305:Dose-Response Relationship, Drug; D018274:Electroporation / Q000379:methods; D004963:Estrenes / Q000494:pharmacology; D051157:Frizzled Receptors / Q000235:genetics / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000096:biosynthesis / Q000235:genetics; D007093:Imidazoles / Q000494:pharmacology; D008647:Mesocricetus; D009474:Neurons / Q000166:cytology* / Q000502:physiology; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D011760:Pyrrolidinones / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013449:Sulfonamides / Q000494:pharmacology; D013997:Time Factors; D051153:Wnt Proteins / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D000096926:Benzenesulfonamides
D001896:Boron Compounds; D002118:Calcium; D002121:Calcium Channel Blockers; D004963:Estrenes; D051157:Frizzled Receptors; D049452:Green Fluorescent Proteins; D007093:Imidazoles; D010726:Phosphodiesterase Inhibitors; D011760:Pyrrolidinones; D034741:RNA, Small Interfering; D020794:Receptor Protein-Tyrosine Kinases; D013449:Sulfonamides; D051153:Wnt Proteins; C473783:2,4,6-trimethyl-N-(meta-3-trifluoromethylphenyl)benzenesulfonamide; D000096926:Benzenesulfonamides; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; C109986:2-aminoethoxydiphenyl borate; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole