Patterning of the head in hydra as visualized by a monoclonal antibody: II. The initiation and localization of head structures in regenerating pieces of tissue☆

摘要

Thebodycolumnofhydraispolarizedsuchthatanewheadwillregeneratefromtheapicalendwhenbothextremitiesareremoved.Thisisduetoagradedpropertyofthetissuetermedtheheadactivationgradient.Theaimoftheexperimentspresentedherewastodeterminewhateventsconnectatwo-dimensionalsegmentoftheactivationgradientinanisolatedpieceoftissuewiththeformationofaheadstructureataparticularlocation.Tothisend,tissuepieceswiththreedifferentshapeswereexcisedandanalyzedduringandafterregeneration.ThemostapicaltissueofeachpiecewaslabeledwiththeDNA-intercalatingdye,DAPI,andtheareawheredevelopmentalchangeswereoccurringwasmonitoredusingthemonoclonalantibodyCP8(Javoisetal.,1986).First,itwasshownthatpolarityofregenerationwasmaintainedregardlessofthefractionofbodylengthincludedintheexcisedpieces.Second,whileheadstructuresusuallyformedfromtheoriginalapicaltissue,theycouldbelocatedanywhereintheregenerate.Thiswasaneffectofthehealingprocesswhichshapedtheapicaledgedifferentlyindifferentpieces.Third,earlyCP8bindingoccurredinsimilarlyshapedareassuggestingthatpatterningeventswereinitiatedinacontiguousmannerwhereverapicaltissuewaslocated.Andfinally,notalloftheCP8-markedtissuesuccessfullyformedstructures.Apparentlysomeregionswerefavoredtocontinuethepatterningprocess,andtheseinturnextinguishedtheprocessinneighboringregions.