Epithelial-mesenchymal interactions during odontogenesis: I. Isolation of several intercellular matrix low molecular weight methylated RNAs☆

[摘要] Thepresentresultsandthosepreviouslyreported(Slavkinetal.,1969a)showthatembryonictoothprimordiasynthesizeinorganculturefourdiscretemethylatedRNAspecies(7S,5S,4S,and2S)isolatedfromtheintercellularmatrixinterposedbetweenepitheliaandmesenchyme.TheseRNAspecieswerefirstseparatedbygelexclusionchromatographyandsubsequentlyresolvedwithpolyacrylamidegeldiscelectrophoresis.Resolutionrequiredemploymentofavarietyofnucleicacidprecursors,labeledmethyl-methionine,liquidscintillationspectrometry,andautoradiography.Thelabeledprecursorsareinitiallyincorporatedintobothepithelialandmesenchymalcells,primarilyinthegerminativeorcervicalregionofthetoothprimordia.Subsequently,smallamountsofRNaselabilematerial(s)areobservedovertheintercellularmatrix;presumablytransferredfrombothcelltypes.Tritiatedthymidineisnotfoundasacomponentoftheintercellularmatrix;deoxyriboseisnotfoundintheisolatedmatrices.Variouslabelscannotbeincorporatedintotheintercellularmatrixintheabsenceofassociatedcellpopulations.Thekineticsoflabelingwithinthecomponents,bothcellpopulationsandmatrix,havebeeninvestigatedusingautoradiography(Slavkinetal.,1969a).Onthebasisofgraincounts,only2%ofthetotalgraindensityincorporatedwithinthisepithelial-mesenchymalsystemistransferredintotheintercellularmatrix;Dactinomycininhibitsthisprocess.Thisspecificintercellularmatrixhasrecentlybeenshowntoenhancehomotypiccellulardifferentiationinvitro(Slavkinetal.,1969b).Ultrastructuralfindingsindicatethepresenceofmembrane-bound,electrondensematerial(500–3000Ã…diameter)withinthematrixpriortophenolextraction;thismaterialisnotpresentinphenol-extractedmatrices.WhethertheextractedintercellularRNAsaretobefoundwithinthemembrane-boundmaterialobservedwithinthematrixinsitu(Slavkinetal.,1969b,c)isnotasyetcertain.Furtherstudiesdesignedtoevaluatethisbiologicalactivity(Slavkinetal.,tobepublished)suggestthattheactivityisRNasesensitive.Astothemechanism(s)forthetransferofRNAorpossiblyribonucleoproteinduringepithelial-mesenchymalinteractions,thepresentexperimentsdonotprovideadequateevidencewithwhichtounderstandthedevelopmentalspecificityoftheisolatedRNAspecies.

[学科分类] 生物科学（综合）