The choroid plexus (ChP) is a secretory tissue responsible for producing cerebrospinal fluid (CSF) in the vertebrate brain. CSF flows from the ...SkiptomaincontentThankyouforvisitingnature.com.YouareusingabrowserversionwithlimitedsupportforCSS.Toobtainthebestexperience,werecommendyouuseamoreuptodatebrowser(orturnoffcompatibilitymodeinInternetExplorer).Inthemeantime,toensurecontinuedsupport,wearedisplayingthesitewithoutstylesandJavaScript.AdvertisementnaturenaturereviewsneurosciencereviewarticlesarticleSubjectsCellfateandcelllineageCerebrospinalfluidproteinsStemcellsinthenervoussystemKeyPointsThechoroidplexus(ChP)isasecretorytissuefoundineachofthebrainventricles,themainfunctionofwhichistoproducecerebrospinalfluid(CSF).AlthoughtheChP–CSFsystemisessentialforproperdevelopmentofthenervoussystemowingtofluidpressurewithintheventriclesaswellasmyriadCSF-bornesignallingfactors,itisneverthelessoneofthemostunderstudiedareasofneurobiology.Ahighlyorganizedtissue,theChPconsistsofsimplecuboidalepithelialcellssurroundingacoreoffenestratedcapillariesandconnectivetissue.AstheinterfacebetweenperipheralcirculationandtheCNS,theChPformstheblood–CSFbarrierviatightjunctionsbetweenadjacentepithelialcellstorestrictfreepassageofsolutesfrombloodintoCSF,andviceversa.TheChPispresentinchordatesabovethelancelet,anditsdevelopment,whichisclassicallycategorizedintofourstagesonthebasisofitshistologicalappearance,occursinastereotypedmanner.Further,theorderofChPdevelopmentseemstobeconservedacrossspecies,withthehindbrain(fourthventricle)ChPappearingfirst,followedbythebilateralappearanceofthetelencephalic(lateralventricle)ChP,andthediencephalic(thirdventricle)ChPappearinglast.Thecell-intrinsicand-extrinsicmolecularmechanismsthatregulateChPdevelopmentarejustnowbeingelucidated.AlthoughChPepithelialcellsarederivedfromneuroepithelialprogenitors,theyarenon-neuralcellsintheirmaturestate,suggestingtheneedtosuppressneuralcharacterinfavourofanon-neuralcellfate.Geneticfate-mappingstudieshaveillustratedthatcellscontr