The Dynamic Expression Pattern of frzb-1 Suggests Multiple Roles in Chick Development

[摘要] TheWntfamilyofsecretedproteinshasbeenshowntohavemultiplerolesinembryonicdevelopment.Wntsignalsarethoughttobepropagatedbybindingtothecysteine-richextracellulardomain(CRD)ofFrizzled,aseven-transmembrane-domaincellsurfacereceptor.SecretedFrizzled-relatedproteins(generallydenotedFrzborSfrp)possessadomainwithahighdegreeofsequenceidentityandstructuralsimilaritywiththeCRDofFrizzled.Currentdataindicatethatthecysteine-richdomainofsecretedFrzbproteinscanbindWntproteins,suggestingthepossibilitythatFrzbscompetewithmembrane-boundFrizzledforWntbindingandconsequentlyactascompetitiveinhibitorsofWntsignaling.InordertogainabetterunderstandingofthepotentialrolesofFrzb-1inchickdevelopment,weutilizedthepolymerasechainreactiontoisolateapartialcDNAofthechickorthologueoffrzb-1,cfrzb-1,andcompareditsexpressionpatterntothatofWnt-1,Wnt-3a,Wnt-5a,Wnt-7a,andWnt-8c.Whole-mountinsituhybridizationshaverevealedthreemajorphasesofexpressionforcfrzb-1inthedevelopingchick.Theearliestexpressionofcfrzb-1isincellsfatedtobecomeneuralectoderminstreak-stageembryos.Expressionofcfrzb-1intheneuralectodermcontinuesupthroughstage8.Afterstage8,cfrzb-1expressionisgraduallyattenuatedintheclosingneuraltubeofthetrunkandisconcomitantlyup-regulatedinneuralcrestcells.Finally,cfrzb-1appearsinthecondensingmesenchymeofthebonesinboththelimbandthetrunkinstage25+embryos.Comparativeanalysisofthecfrzb-1andtheWntgeneexpressionpatternssuggestspossibleinteractionsbetweencFrzb-1andalloftheWntfamilymembersexamined.

[学科分类] 生物科学（综合）

[关键词] chick;chondrogenesis;development;embryo;Frizzled;Frzb;gastrulation;Hensen's node;HNK-1;limb;neural crest;neurulation;Sarp;Sfrp;whole-mount in situ hybridization;Wnt