BMP antagonism by Spemann's organizer regulates rostral–caudal fate of mesoderm

摘要

RecentrevisionstotheemXenopus/emfatemapchallengetheinterpretationofpreviousmapsandcurrentmodelsofamphibianaxialpatterning(Lane,M.C.,Smith,W.C.,1999.TheoriginsofprimitivebloodinemXenopus/em:implicationsforaxialpatterning.Development126(3),423ndash;434.;Lane,M.C.,Sheets,M.D.,2000.Designationoftheanterior/posterioraxisinpregastrulaemXenopuslaevis/em.Dev.Biol.225,37ndash;58).Wedeterminedtherostralmostcontributionstobothdorsalandventralmesodermconcomitantlyfrommarginalzoneprogenitorsinstage6embryos.Datarevealanunequivocalrostral-to-caudalprogressionofbothdorsalandventralmesodermacrossthepre-gastrulaaxishistoricallycalledthedorsalndash;ventralaxis,andadorsal-to-ventralprogressionfromanimal-to-vegetalinthemarginalzone.Thesefindingssupporttheproposedrevisionstothefateandaxisorientationmaps.Mostimportantly,theseresultsraisequestionsabouttheroleoftheorganizergraftsandorganizer-derivedBMPantagonistsintheldquo;inductionrdquo;ofsecondaryaxes.Were-examinebothphenomena,andfindthatorganizergraftsandBMPantagonistsevokecaudal-to-rostralmesodermalfatetransformations,andnotventral-to-dorsaltransformationsascurrentlybelieved.WedemonstratethatBMPantagonismevokesasecondaxisbecauseitstimulatesprecociousmediolateralintercalationofcaudal,dorsalmesoderm.Theimplicationsofthesefindingsformodelsoforganizerfunctioninvertebrateaxialpatterningarediscussed./p/div