Developmental genetic basis for the evolution of pelvic fin loss in the pufferfish Takifugu rubripes

摘要

Pairedappendageswereakeydevelopmentalinnovationamongvertebratesandtheyeventuallyevolvedintolimbs.Ancientdevelopmentalcontrolsystemsforpairedfinsandlimbsarebroadlyconservedamonggnathostomevertebrates.Somelineagesincludingwhales,somesalamanders,snakes,andmanyray-finfish,independentlylostthepectoral,pelvic,orbothappendagesoverevolutionarytime.Whendifferenttaxaindependentlyevolvesimilardevelopmentalmorphologies,dotheyusethesamemoleculargeneticmechanisms?TodeterminethedevelopmentalgeneticbasisfortheevolutionofpelvislossinthepufferfishemTakifugurubripes/em(fugu),weisolatedfuguorthologsofgenesthoughttobeessentialforlimbdevelopmentintetrapods,includinglimbpositioning(emHoxc6/em,emHoxd9/em),limbbudinitiation(emPitx1/em,emTbx4/em,emTbx5/em),andlimbbudoutgrowth(emShh/em,emFgf10/em),andstudiedtheirexpressionpatternsduringfugudevelopment.Resultsshowedthatbudoutgrowthandinitiationfailtooccurinfugu,andthatpelvislossisassociatedwithalteredexpressionofemHoxd9a/em,whichweshowtobeamarkerforpelvicfinpositioninthree-spinesticklebackemGasterosteusaculeatus./emTheseresultsruleoutchangesinappendageoutgrowthandinitiationgenesastheearliestdevelopmentaldefectinpufferfishpelvicfinlossandsuggestthatalteredemHoxd9a/emexpressioninthelateralmesodermmayaccountforpelvislossinfugu.Thismechanismappearstobedifferentfromthemechanismforpelviclossinstickleback,showingthatdifferenttaxacanevolvesimilarphenotypesbydifferentmechanisms./p/div