Gene expression changes at metamorphosis induced by thyroid hormone in Xenopus laevis tadpoles

摘要

Thyroidhormone(TH)controlledgeneexpressionprofileshavebeenstudiedinthetail,hindlimbandbraintissuesduringTH-inducedandspontaneousemXenopuslaevis/emmetamorphosis.AmplifiedcRNAprobesmixedwithauniversalstandardwerehybridizedtoasetof21,807-sensestrand60-meroligonucleotidesoneachsliderepresentingtheentriesinemX.laevis/emUniGeneBuild48.Mostoftheup-regulatedgenesinhindlimbandbrainarethesame.ThisreflectsinpartthefactthattheinitialresponsetoTHinductioninbothtissuesiscellproliferation.Alargenumberofup-regulatedgenesinthelimbandbrainprogramsencodecommoncomponentsofthecellcycle,DNAandRNAmetabolism,transcriptionandtranslation.Notchisoneofthefewgenesthatisdifferentiallyexpressedexclusivelyinthebraininthefirst48hofTHinductionstudiedintheseexperiments.TheTH-inducedgeneexpressionchangesinthetailaredifferentfromthelimbandbrainprograms.Distinctmuscleandfibroblastprogramswereidentifiedinthetail.Dyingmusclefibersintail(markedbyactivecaspase-3)up-regulateagroupofgenesthatincludeproteolyticenzymes.Attheclimaxofmetamorphosis,tailmuscledown-regulatesmorethanhalfofthegenesthatencodetheglycolyticenzymesinthecytoplasmandthetricarboxylicacidpathwayandallfivecomplexesoftheelectrontransportsysteminmitochondria.Thesechangesingeneexpressionprecedetheactivationofcaspase-3.Someofthesesameenergymetabolism-relatedgenesareup-regulatedinthelimbandbrainprogramsbyTH.Aprominentfeatureofthetailfibroblastsisthedown-regulationofseveralcollagenandotherextracellularmatrixgenesandtheup-regulationofhydrolyticenzymesthatareresponsiblefordissolvingthenotochordandresorbingthetail./p/div