Interplay of mutant and wild-type pigment cells in chimeric leopard frogs☆

[摘要] Thesemidominantmutantgeneburnsi(B)suppressestheformationofthedorsalspots(aggregationsofdermalmelanophores)thatconferuponthewild-typefrog(Ranapipiens)itscharacteristicleopard-likepattern.Mutantactionwasappraisedbyanalyzingtheinteractionofcontiguousburnsiandwild-typetissuesinexperimentallyproducedchimericfrogs.Twoembryosinearlytailbuddevelopment,oneburnsi(Bb)andtheotherwild-type(bb),wereeachcutinhalfacrossthemiddleofthebody,andthegeneticallydifferentfronthalveswereinterchanged.Twenty-fourchimericembryoswerecarriedthroughandbeyondmetamorphosis,ofwhich13comprisedtheunionofanteriorburnsihalvestoposteriorwild-typehalves(burnsi:wild-type)and11representedthereversefusion(wild-type:burnsi).Theprimaryobjectivewastodeducewhetherfactorsendogenousorexogenoustothespot-formingmelanophoresareprimarilyresponsibleforthedifferenceinmutantandwild-typepigmentarypatterns.Itappearsthatthemutantburnsigenealtersprincipallytheintrinsicpropertiesofthemelanoblasts.Thatthepigmentcellismodifiedinsomewaybythemutantgeneissuggestedbythefailure,toavariableextent,ofwild-typemelanoblaststoformspotsintheposteriorhalfofaburnsi:wild-typechimericfrog.Aprovisionalinterpretationisthatburnsipropigmentcellsinfiltratetheposteriorwild-typeterrainandinhibitorcurtailtheaggregativemovementsofthewild-typemelanoblasts.Theantagonisticinfluencesoftheburnsimelanoblastsmaywaneastheycompletetheirdifferentiation.Accordingly,someofthewild-typepigmentcells,previouslyheldinabeyance,maythensatisfytheirinherenttendencytocongregateintospots.Inthereciprocalchimericcombination,wild-type:burnsi,itislikelythatthewild-typemelanoblastsinvadetheburnsiterrain.Onceagain,impeditiveactivitiesofresidentburnsimelanoblastsapparentlypreventtheemigrantwild-typepigmentcellsfromfulfillingtheiraggregativepotential.Itmaybethoughtthatanaccessoryinhibitingfactorissomeunfavorableconditioninthetissueenvironmentofthemelanoblasts,butdatafromotherlinesofinquiryindicatethattheburnsienvironmentaltissueissuitableforthedifferentiationofwild-typemelanoblasts.

[学科分类] 生物科学（综合）