Germ lineage properties in the urochordate Botryllus schlosseri – From markers to temporal niches

摘要

Theprimordialgermcells(PGCs)inthecolonialurochordateemBotryllusschlosseri/emaresequesteredinlateembryonicstage.PGC-likepopulations,locatedatanyblastogenicstageinspecificniches,insidemoduleswithcurtailedlifespan,survivethroughoutthelifeofthecolonybyrepeatedweeklymigrationtonewlyformedbuds.ThiscyclicalmigrationandthelackofspecificmarkersforPGC-likepopulationsareobstaclestothestudyonPGCs.Forthatpurpose,weisolatedtheemBotryllus/emDDX1(BS-DDX1)andcharacterizeditbynormalexpressionpatternsandbyspecificsiRNAknockdownexperiments.ExpressionofBS-DDX1concurrentwithBS-Vasa,γ-H2AX,BS-cadherinandphospho-Smad1/5/8,demarcatePGCcellsfromsomacellsandfrommoredifferentiatedgermcellslineages,whichenabledthedetectionofadditionalputativetransientnichesinzooids.EmployingBS-cadherinsiRNAknockdown,retinoicacid(RA)administrationorβ-estradioladministrationaffirmedtheBS-Vasasup+/supBS-DDX1sup+/supBS-cadherinsup+/supγ-H2AXsup+/supphospho-Smad1/5/8sup+/suppopulationastheemB.schlosseri/emPGC-likecells.BystrivingtounderstandthePGC-likecellstraffickingbetweentransientnichesalongblastogeniccycles,CM-DiI-stainedPGC-likeenrichedpopulationsfromlateblastogenicstageDzooidswereinjectedintogeneticallymatchedcolonialrametsatblastogenicstagesAorCandtheirfateswereobservedfor9days.Basedontheaccumulateddata,weconceivedanovelnetworkofseveraltransientandshortlivedlsquo;germlinenichesrsquo;thatpreservePGCshomeostasis,protectingthesecellsfromtheweeklyastogenicsenescenceprocesses,thusenablingthesurvivalofthePGCsthroughouttheorganism'slife./p/div