Spatial and temporal patterns of cell death in limb bud mesoderm after apical ectodermal ridge removal☆

[摘要] Aspatiotemporalpatternofcelldeathoccurredinthechickwingandlegbudmesodermafterremovalofapicalectodermalridgeatstages18–20.Cellsdiedinaregionextendingfromthelimbbuddistalsurfaceto150–200μmintothemesoderm.Limbbudsfromwhichridgewasremovedatlaterstagesindevelopmentdidnotexhibitaspatiotemporalpatternofcelldeath.Incontrolexperimentsinwhichdorsalectodermwasremoved,apatternofcelldeathdidnotoccur.Removaloftheridgeandpartofthe150-to200-μmzoneofprospectivecelldeathresultedincelldeathinanareaapproximatelyequaltotheamountofthezoneremaining.Afterremovalofalloftheprospectivezoneofcelldeathplustheapicalridge,celldeathwasobservedintheremaininglimbbudmesoderm.Intheselimbbuds,celldeathoccurredinaregioninwhichithadnotbeenseeninlimbbudwithapicalridgealoneremoved.Weconcludethatatstages18–20themesodermalcells150–200μmbeneaththeridgerequiretheapicalridgetosurvive.Moreproximalmesodermalcellsdonotdieafterridgeremovalalone,butapparentlyrequirethepresenceofthemoredistalmesodermtosurvive.Whetherthisisarequirementforsomethingintrinsictothedistalmesodermorsomethingitpossessesbywayoftheridgeisunknown.Afterstage23,thelimbmesodermcellsdonotdiewhentheapicalridgeisremoved.Nevertheless,atthelaterstages,ridgecontinuestoberequiredforlimbbudproximal-distalelongationandthedifferentiationofdistallimbelements.

[学科分类] 生物科学（综合）