Patterning the Early Zebrafish by the Opposing Actions of bozozok and vox/vent

[摘要] Fishandfrogembryosarepatternedalongthedorsalndash;ventralaxisduringthegastrulastagebyopposinggradientsofBmpsandBmpinhibitoryproteins.ThreetranscriptionalrepressorswithpartiallyoverlappingexpressiondomainshavebeenproposedtobeimportantmediatorsofBmpfunctioninXenopus.Wefindthattworelatedfactorsareexpressedintheearlyzebrafishembryo.AlthoughthesefactorsareconsiderablydivergentfromtherelatedXenopusgenes,theyareexpressedindomainssimilartothoseoftheirXenopusrelativesthroughoutembryogenesis.Bothofthezebrafishgenes,whichwehavenamedvoxandvent,arepotentventralizingfactorsinbothzebrafishandXenopusembryos.UsingmutantsintheBmppathway,wefindthatthereareBmp-dependentandBmp-independentdomainsofvoxexpression,whereasventismostlydependentuponBmpsignaling.Weshowthatectopicvoxorventnegativelyregulatesexpressionoftheearlydorsalgenebozozok(boz)andthatectopicbozeliminatesvoxandventexpression.Moreover,thenormalexclusionofvoxandventfromtheorganizerregionislostinbozmutantembryos.Ourresultsshowthatbozandvox/ventaremutuallyantagonisticandindicatethattheearlyestablishmentofthesizeoftheorganizerdomainisdependentonaninterplaybetweentheseearlyexpressedtranscriptionalrepressors.