Distinct and cooperative roles of mammalian Vg1 homologs GDF1 and GDF3 during early embryonic development

摘要

Vg1,amemberoftheTGF-βsuperfamilyofligands,hasbeenimplicatedintheinductionofmesoderm,formationofprimitivestreak,andleftndash;rightpatterninginemXenopus/emandchickembryos.Inmice,GDF1andGDF3ndash;twoTGF-βsuperfamilyligandsthatsharehighsequenceidentitywithVg1ndash;havebeenshowntoindependentlymimicdistinctaspectsofVg1'sfunctions.However,theextenttowhichthedevelopmentalprocessescontrolledbyGDF1andGDF3andtheunderlyingsignalingmechanismsareevolutionarilyconservedremainsunclear.HereweshowthatphylogeneticandgenomicanalysesindicatethatemGdf1/emisthetrueemVg1/emorthologinmammals.Inaddition,andsimilartoGDF1,wefindthatGDF3signalingcanbemediatedbythetypeIreceptorALK4,typeIIreceptorsActRIIAandActRIIB,andtheco-receptorCriptotoactivateSmad-dependentreportergenes.Whenexpressedinheterologouscells,thenativeformsofeitherGDF1orGDF3wereincapableofinducingdownstreamsignaling.Thiscouldbecircumventedbyusingchimericconstructscarryingheterologousprodomains,orbyco-expressionwiththeFurinpro-proteinconvertase,indicatingpoorprocessingofthenativeGDF1andGDF3precursors.Unexpectedly,co-expressionwithNodalndash;anotherTGF-βsuperfamilyligandinvolvedinmesodermformationndash;couldalsoexposetheactivitiesofnativeGDF1andGDF3,suggestingapotentiallynovelmodeofcooperationbetweentheseligands.FunctionalcomplementaritybetweenGDF1andGDF3duringembryonicdevelopmentwasinvestigatedbyanalyzinggeneticinteractionsbetweentheircorrespondinggenes.ThisanalysisshowedthatemGdf1/emsupemminus;/minus;/em/supem;Gdf3/emsupemminus;/minus;/em/supcompoundmutantsaremoreseverelyaffectedthaneitheremGdf1/emsupemminus;/minus;/em/suporemGdf3/emsupemminus;/minus;/em/supsinglemutants,withdefectsintheformationofanteriorvisceralendodermandmesodermthatrecapitulateVg1lossoffunction,suggestingthatGDF1andGDF3togetherrepresentthefunctionalmammalianhomologsofVg1./p/div