The spatial distribution of maternal mRNA is determined by a cortical cytoskeletal domain in Chaetopterus eggs☆

摘要

MessengerRNAmoleculesarelocalizedinthecorticalregionofeggsandunevenlysegregatedtotheembryoniccellsduringearlydevelopmentoftheannelidChaetopterus.Theeggcortexisenrichedintwoorganelles,ectoplasmicspherulesandassociatedstructures,whicharesimilarinappearancetonuage.ThephysicalbasisofcorticalmRNAlocalizationwasexaminedinstratifiedeggsandineggsextractedwiththenonionicdetergentNonidetP-40(NP-40).Thecorticalorganellesweredisplacedtothemostcentrifugalzoneofstratifiedeggs.Insituhybridizationwithpoly(U)orclonedDNAprobesshowedthatalargeproportionofthepoly(A)+RNA,histonemRNA,andactinmRNAmoleculeswasalsodisplacedtothecentrifugalzone.ExtractionwithNP-40revealedadetergent-insolublecytoskeletaldomain(CD)intheeggcortexwhichcontainedtheremnantsofectoplasmicspherulesandnuageembeddedinafibrousnetwork.AlthoughmostofthetotalproteinandRNAwasextractedbyNP-40,alargeproportionofthepoly(A)+RNA,histonemRNA,andactinmRNAmoleculeswasretainedintheCD.InsituhybridizationofstratifiedeggsextractedwithNP-40indicatedthattheCD,withitsassociatedorganellesandmRNAmolecules,isdisplacedtothecentrifugalzoneasaunit.TheresultssuggestthatthetenaciousassociationofmRNAmoleculeswiththecorticalCDmayberesponsibleformaternalmRNAlocalizationduringearlydevelopment.