Embryonic Expression of Lim-1, the Mouse Homolog of Xenopus XLim-1, Suggests a Role in Lateral Mesoderm Differentiation and Neurogenesis

[摘要] cDNAsencodedbythemousehomolog(Lim-1)oftheXenopusLIM-classhomeoboxgeneXlim-1havebeenisolatedfroman8.5-daymouseembryocDNAlibrary.NucleotideanddeducedaminoacidsequencesshowahighdegreeofidentitywithXlim-1intheLIMandhomeodomains,and85%identityoverthewholeprotein.AninterspecificbackcrosshasbeenusedtoshowcloselinkageofLim-1totheendogenousproviralmarkerMpmv-4onmousechromosome11.Wholemountinsituhybridizationstudieshavebeencarriedoutonmouseembryosbetween6.5and10.5days.Inmid-tolate-streakstageembryos,Lim-1isexpressedinarestrictedregionofmesodermintheprimitivestreak,withthehighestlevelofsignalattheanterior.At7.5days,transcriptscanbeseeninahorseshoe-shapedpatternintheperipheryofthenode,aswellasalongbothsidesoftheimmediatelyadjacentnotochord.Inaddition,transcriptsarepresentinpresumptivelateralandintermediatemesoderm.Later,expressionbecomesprogressivelyrestrictedtointermediatemesoderm,thenephrogeniccords,andeventuallymesonephricductsandtubules.By10.5daysLim-1transcriptsalsoappearinrestrictedregionsofthecentralnervoussystem(CNS)thatareassociatedwithsensoryfunction.Thelateraldiencephalon,hindbrain,andpresumedcommissuralneuronsinthedorsalspinalcordallshowLim-1expression.Intheadult,Lim-1isexpressedinthecerebellum/medullaandkidney,andatverylowlevelsinthecerebrum.ThesedatasuggestthatinthemouseembryoLim-1playsaroleinearlymesodermformationandlaterspecificationofadifferentiatedphenotypeinsubsetsofcellsofthemesonephrosandsensoryneuronsoftheCNS.