Pathways and mechanisms of avian trunk neural crest cell migration and localization☆

[摘要] Crestcellsindividualizedatthedorsalborderoftheneuraltube,whiletheybecamesurroundedbyafibronectin-richmatrix.Crestcellsinitiatedtheirmigrationbetweenthebasementmembranesoftheneuraltubeandtheectoderm.Inthevagalregion,crestcellsmigratedinafibronectin-richenvironmentbetweentheectodermandthedermomyotome,veryrapidlyreachingtheapexofthepharynx.Inthetrunkregion,crestcellsoppositethebulkofthesomiteaccumulatedatthejunctionbetweenthesomite,theneuraltube,andtheectoderm;theyresumedtheirmigrationattheonsetofthedissociationofthesomiteintodermomyotomeandsclerotome.Migrationoccurredmoreventrallyalongtheneuraltube;nevertheless,theformationoftherapidlyexpandingsclerotomepreventedcrestcellsfromreachingtheparanotochordalregion.Thereafter,crestcellsaccumulatedbetweentheneuraltube,thedermomyotome,andthesclerotome,whereultimatelytheyformedthedorsalrootganglia.Incontrast,cellsoppositetheintersomiticspacedidnotencountertheseobstaclesandutilizedanarrowpathwayformedbetweenthebasementmembranesofthetwoadjacentsomites.Thispathwayallowedcrestcellstoreachthemostventralregionsoftheembryoveryrapidly;theyaccumulatedalongtheaortatoformtheaorticplexuses,theadrenalmedulla,andthesympatheticganglia.Thebasicfeaturesofthemigrationpathwaysare(1)astrictdelimitationbythefibronectin-richbasementmembranesofthesurroundingtissues,(2)aformationofspaceconcomitantwiththemigrationofcrestcells,(3)atransientexistence:continuedmigrationiscorrelatedwiththepresenceoffibronectin,whereascessationiscorrelatedwithitsfocaldisappearance.Thecrestcellsarecharacterizedbytheirinabilitytotraversebasementmembranesandpenetratewithintissues.Weproposethatthecombinationofactiveproliferation,uniquemotilityproperties,andthepresenceofnarrowpathwaysarethemajormechanismsensuringcorrectdirectionality.Morphologicallydefinedtransientroutesofmigrationalongwithdevelopmentallyregulatedchangesintheextracellularmatrixandintheadhesivepropertiesofcrestcellsaremostprobablyinvolvedintheirstabilizationindefinedterritoriesandtheiraggregationintoganglia.

[学科分类] 生物科学（综合）