Changes in reaggregation pattern during neural tube differentiation☆

[摘要] Reaggregationexperimentswereperformedontheneuraltubefrom3-to6-day-oldchickembryos.Stage-dependentchangesinthereaggregationpatternoftheneuralcellsstudiedwerefound.While4-day-oldopticlobeaggregatesdevelopagreatnumberofepithelialrosettesafter24hours'culture,rosettesdonotappearwhenthesametissuetakenfrom5-or6-day-oldembryosisdissociatedandculturedunderthesameconditions.Inculturesfromtheseolderembryos,theformationofafibrillarlayerattheperipheryoftheaggregatesappearsasthemostprominentmorphologicalfeatureoftheirdifferentiation.Three-day-old(HamburgerandHamiltonstages18–20)opticlobeaggregatesonlyexceptionallyshowrosettes,andneverdowhenopticlobefromstage18embryosisused.However,whensuspensionsofstage18-opticlobe,andof6-day-oldopticlobearemixedwitheachotherandallowedtoreaggregate,theresultingaggregatesshowmanyrosettes.Formationofrosettesinculturesof4-day-oldopticlobeseemstobeaccomplishedbyinvaginationof“placodelike”structurespresentattheperipheryoftheaggregatesduringthefirsthoursofculture.Thecellsintherosettesresemblethoseintheearlyembryonicneuraltubeintheirstructureandmitoticbehavior.Ithasbeenproposedintheliteraturethatrosetteformationistheexpressionofaparticularcapacityofthe“neuroepithelial”cells.Ourresultssuggestthat,evenifthisisthecase,thepresenceoftherightproportionsof“differentiating”cellsmaybenecessaryforrosetteformationtooccur.Labelingexperimentsusing6-day-oldopticlobeshowthattheDNA-synthesizing(“matrix”)cellsandthenon-DNA-synthesizing(“differentiating”)cellssortoutfromeachother,thesecondtypeofcellsbeingpresentinhighernumbersattheperipheryoftheaggregates.Inthe6-day-oldopticlobeaggregatesboththeformationofaperipheralfibrillarlayerandthesortingoutofthenon-DNA-synthesizingcellstowardtheperipheryresembleprocessesnormallyoccurringduringneuraltubedevelopment.Unlabeled4-,5-or6-day-oldchickembryotelencephaloncellsuspensionsform,after24hours'culture,aggregateswhosestructureissimilartothatofequivalentopticlobeaggregates.When4-or6-day-oldopticlobeaggregatesobtainedafter24hoursofculturearegrownaschorioallantoicgraftsfor8daysmanyneuroblastlikecellsareobserved,butnoindicationsoftheformationoftheconcentriclayerstypicaloftheopticlobearefound.

[学科分类] 生物科学（综合）