Temporal and Spatial Effects of Sonic Hedgehog Signaling in Chick Eye Morphogenesis

[摘要] Properdorsal–ventralpatternformationoftheopticcupisessentialforvertebrateeyemorphogenesisandretinotectaltopographicmapping.Previousstudieshavesuggestedthatmidlinetissue-derivedSonichedgehog(Shh)moleculesplaycriticalrolesinestablishingthebilateraleyefieldsandindeterminingtheproximal–distalaxisoftheeyeprimordium.Here,wehaveexaminedthetemporalrequirementsforShhduringtheopticvesicletoopticcuptransitionandafterearlyopticcupformationinchickembryos.BothmisexpressingShhbyvirusandblockingShhactivitybyantibodiesresultedindisruptionofventraloculartissues.DecreasingendogenousShhsignalsunexpectedlyrevealedasharpmorphologicalboundarysubdividingdorsalandventralportionsoftheopticcup.Inaddition,Shhsignalsdifferentiallyinfluencedexpressionpatternsofgenesinvolvedinoculartissuespecification(Pax6,Pax2,andOtx2)anddorsal–ventralpatterning(cVax)withintheventralbutnotdorsalopticcup.EctopicShhsuppressedexpressionofBoneMorphogeneticProtein4(BMP4)inthedorsalretina,whereasreducingendogenousSonichedgehogactivityresultedinaventralexpansionofBMP4territory.TheseresultsdemonstratethattemporalrequirementsforShhsignalspersistaftertheformationoftheopticcupandsuggestthattheearlyvertebrateopticprimordiummaybesubdividedintodorsalandventralcompartments.WeproposeamodelinwhichventrallyderivedShhsignalsanddorsallyrestrictedBMP4signalsactantagonisticallytoregulatethegrowthandspecificationoftheopticprimordium.

[学科分类] 生物科学（综合）

[关键词] eye;chick;dorsal–ventral;Sonic hedgehog;BMP4;Vax;Pax6;Pax2;Otx2.