The Evolution of Chordate Neural Segmentation

Developmental Biology

Sebastian M. Shimeld¹  Françoise Mazet¹ 

[1] School of Animal and Microbial Sciences, The University of Reading, P.O. Box 228, Whiteknights, Reading, RG6 6AJ, United Kingdom

关键词: amphioxus;    FoxB;    SIM;    brain evolution;    hindbrain;    rhombomeres;    segmentation;   

DOI  :  10.1006/dbio.2002.0831

学科分类：生物科学（综合）

来源: Academic Press

【 摘 要 】

Amphioxusistheclosestrelativetovertebratesbutlackskeyvertebratecharacters,likerhombomeres,neuralcrestcells,andthecartilaginousendoskeleton.Thisreflectsmajordifferencesinthedevelopmentalpatterningofneuralandmesodermalstructuresbetweenbasalchordatesandvertebrates.Here,weanalysetheexpressionpatternofanamphioxusFoxBorthologandanamphioxussingle-mindedorthologtogaininsightintotheevolutionofvertebrateneuralsegmentation.AmphiFoxBexpressionshowscrypticsegmentationofthecerebralvesicleandhindbrain,suggestingthatneuromericsegmentationofthechordateneuraltubearosebeforetheoriginofthevertebrates.Intheforebrain,AmphiFoxBexpressioncombinedwithAmphiSimandotheramphioxusgeneexpressionpatternsshowsthatthecerebralvesicleisdividedintoseveraldistinctdomains:weproposehomologybetweenthesedomainsandthesubdivideddiencephalonandmidbrainofvertebrates.IntheHox-expressingregionoftheamphioxusneuraltubethatishomologoustothevertebratehindbrain,AmphiFoxBshowsthepresenceofrepeatedblocksofcellsalongtheanterior–posterioraxis,eachalignedwithasomite.Thisandotherdataleadustoproposeamodelfortheevolutionofvertebraterhombomericsegmentation,inwhichrhombomereevolutioninvolvedthetransferofmechanismsregulatingneuralsegmentationfromverticalinductionbyunderlyingsegmentedmesodermtohorizontalinductionbygradedretinoicacidsignalling.Aconsequenceofthiswouldhavebeenthatsegmentationofvertebrateheadmesodermwouldnolongerhavebeenrequired,pavingthewayfortheevolutionoftheunsegmentedheadmesodermseeninlivingvertebrates.

【 授权许可】

Unknown