The central nervous system of the ascidian larva: mitotic history of cells forming the neural tube in late embryonic Ciona intestinalis

摘要

Ascidianlarvaedevelopafteraninvariantpatternofembryoniccleavage.Fewerthan400cellsconstitutethelarvalcentralnervoussystem(CNS),whichformswithouteitherextensivemigrationorcelldeath.WecataloguethemitotichistoryofthesecellsinemCionaintestinalis/em,usingconfocalmicroscopyofwhole-mountembryosatstagesfromneurulationuntilhatching.ThepositionsofcellscontributingtotheCNSwerereconstructedfromconfocalimagestacksofembryonicnuclei,andmapsofsuccessivestageswereusedtochartthemitoticdescent,therebycreatingacelllineageforeachcell.TheentireCNSisformedfrom10th-to14th-generationcells.Althoughminordifferencesexistincellposition,lineageisinvariantincellsderivedfromA-lineblastomeres,whichformthecaudalnervecordandvisceralganglion.Wedocumentthelineageoffivepairsofpresumedmotorneuronswithinthevisceralganglion:onepairarisesfromA/spanid="mmlsi78"class="mathmlsrc"imgclass="imgLazyJSBinlineImage"height="13"width="14"alt="Full-sizeimage(1K)"style="margin-top:-5px;vertical-align:middle"title="Full-sizeimage(1K)"src="/sd/grey_pxl.gif"data-inlimgeid="1-s2.0-S0012160604002362-si78.gif"noscriptimgheight="13"border="0"style="vertical-align:bottom"width="14"alt="Full-sizeimage(1K)"title="Full-sizeimage(1K)"src="http://origin-ars.els-cdn.com/content/image/1-s2.0-S0012160604002362-si78.gif"oscript!--ja:math--/span10.57,andfourfromprogenyofA/spanid="mmlsi79"class="mathmlsrc"imgclass="imgLazyJSBinlineImage"height="13"width="14"alt="Full-sizeimage(1K)"style="margin-top:-5px;vertical-align:middle"title="Full-sizeimage(1K)"src="/sd/grey_pxl.gif"data-inlimgeid="1-s2.0-S0012160604002362-si79.gif"noscriptimgheight="13"border="0"style="vertical-align:bottom"width="14"alt="Full-sizeimage(1K)"title="Full-sizeimage(1K)"src="http://origin-ars.els-cdn.com/content/image/1-s2.0-S0012160604002362-si79.gif"oscript!--ja:math--/span9.30.Theremainingcellsofthevisceralganglionareintheir13thand14thgenerationsathatching,withmostmitoticactivityceasingaround85%ofembryonicdevelopment.Oftheapproximately330larvalcellspreviouslyreportedintheCNSofemCiona/em,wedocumentthelineageof226thatderivepredominantlyfromA-lineblastomeres./p/div