Effects of L1 Blockade on Sensory Axon Outgrowth and Pathfinding in the Chick Hindlimb

[摘要] Inthedevelopingchickhindlimb,sensoryaxons,whichgrowtogetherinbundlesastheyextenddistally,andthemotoneuronaxonstheyencounterexpressthecelladhesionmoleculeL1.Followinginjectionoffunction-blockinganti-L1antibodiesintothelimbatstage25,somesensoryaxonschooseinappropriateperipheralnerveseventhoughmotoneuronpathfindingisunaffected.Here,tofurtherelucidateL1'srole,weassessedtheeffectsofthisperturbationusingpathwaytracing,immunelabeling,confocalmicroscopy,andelectronmicroscopy.AfterL1blockade,sensoryaxonswerestillbundledandcloselyapposed.However,clearsignsofdecreasedadhesionweredetectableultrastructurally.Further,sensoryaxonsgrewintothelimbmoreslowlythannormal,wanderingmorewidely,branchingmorefrequently,andsometimesextendingalonginappropriateperipheralnerves.Sensoryaxonsthatultimatelyprojectedalongdifferentcutaneousnervesshowedincreasedintermixinginthespinalnerves,duetoerrorsinpathfindingandalsotoadecreasedabilitytosegregateintonerve-specificfascicles.Theseresultssuggestthat,inthehighlycomplexinvivoenvironment,asintissueculture,L1stimulatesaxongrowthandenhancesfasciculation,andthattheseprocessescontributetotheorderly,timely,andspecificgrowthofsensoryaxonsintothelimb.

[学科分类] 生物科学（综合）

[关键词] pathfinding;fasciculation;L1;sensory axons;cell adhesion molecules;dorsal root ganglia;axon guidance;axon outgrowth;limb innervation;cutaneous nerve