Effects of Localized Application of Retinoic Acid on Xenopus laevis Development

[摘要] Inordertomoreaccuratelydeterminethemechanismbywhichretinoicacidcausesembryonicdefects,wehavedevelopedasimplemethodoflocallyapplyingretinoicacidratherthanimmersingthewholeembryoinretinoicacidsolutions.RetinoicacidwassuspendedincornoilandtheninjectedbetweenthesurfaceandthedeepectodermallayersofanearlygastrulaXenopusembryo.Whendropletscontainingretinoicacidwereinjectedintothepresumptiveheadregion,theembryosexhibitedinhibiteddevelopmentofanteriorstructuresneartheinjectionsite.Developmentoftheeye,cementgland,hatchinggland,olfactorypits,andexpressionofengrailedproteinwerealldisruptedneartheinjectionsite.Inhibiteddevelopmentofanteriorstructureswasfargreaterontheinjectedsideoftheembryothanontheuninjectedside.Theretinoicaciddropletdidnotcauseananteriorshiftofstructuresontheinjectedsiderelativetotheuninjectedside.Theseexperimentssuggestthatretinoicaciddoesnotcauseglobalrespecificationofaxiallevelinthehead,butrathersuppressesdevelopmentofanteriorstructures.Retinoicacidinjectedintopresumptivetrunkregionshadnodiscernibleeffect.