Polaris and Polycystin-2 in dorsal forerunner cells and Kupffer's vesicle are required for specification of the zebrafish left–right axis

摘要

Recently,ithasbecomeclearthatmotileciliaplayacentralroleininitiatingaleft-sidedsignalingcascadeimportantinestablishingtheLRaxisduringmouseandzebrafishembryogenesis.Twogenesproposedtobeimportantinthiscilia-mediatedsignalingcascadeareempolaris/emandempolycystin-2/em(empkd2/em).Polarisisinvolvedinciliaryassembly,whilePkd2isproposedtofunctionasaCasup2+/sup-permeablecationchannel.Wehaveclonedzebrafishhomologuesofempolaris/emandempkd2/em.Bothgenesareexpressedindorsalforerunnercells(DFCs)fromgastrulationtoearlysomitestageswhenthesecellsformaciliatedKupffer'svesicle(KV).Morpholino-mediatedknockdownofPolarisorPkd2inzebrafishresultsinmisexpressionofleft-side-specificgenes,includingemsouthpaw/em,emlefty1/emandemlefty2/em,andrandomizationofheartandgutlooping.BytargetingmorpholinostoDFCs/KV,weshowthatempolaris/emandempkd2/emarerequiredinDFCs/KVfornormalLRdevelopment.PolarismorphantshavedefectsinKVcilia,suggestingthatthelateralityphenotypeisduetoproblemsinciliafunctionperse.Wefurthershowthatexpressionofempolaris/emandempkd2/emisdependentontheT-boxtranscriptionfactorsemnotail/emandemspadetail/em,respectively,suggestingthatthesegeneshaveapreviouslyunrecognizedroleinregulatingciliarystructureandfunction.Ourdatasuggestthatthefunctionsofempolaris/emandempkd2/eminLRpatterningareconservedbetweenzebrafishandmiceandthatKupffer'svesiclefunctionsasaciliatedorganofasymmetry./p/div