Development of neuronal locus specificity in Xenopus retinal ganglion cells after surgical eye transection or after fusion of whole eyes☆

[摘要] Adevelopmentalprogramisestablishedinthestage28–32opticcupofXenopusembryos,whichspecifiesthepermanentAPandDVreferenceaxesforpositionalinformationintheretina,andtherebydeterminesthepatternofspatialdeploymentofganglioncelllocusspecificitiessubservingassemblyofretinotopicallyorganizedconnectionsinthetectum.Thisdevelopmentalprogramhaspreviouslyprovedunmodifiableinintacteyeprimordiasubmittedtoavarietyofrotation,transplantation,andtissuecultureconditions.Herewereportthattheprogramcanbemodifiedbysurgicaltransectionofstage32eyeprimordia(withsubsequentfusionofthedisconnectedhalvestoreconstituteawholeeye)andbyfusionofwholestage38eyes,althoughmostofthetransectedeyesdiddevelopnormalvisuotectalprojections.Theremainingverticallytransectedeyes,andalleyesformedwhenaleftandrightstage38eyefusedalongapposedtemporaledges,developed“double-nasalcompound”projectionstothetectum:thenasalandtemporalhalvesoftheadultretinaeachprojectedtotheentiretectum,andeachtectallocuswasdrivenfromtwostimuluspositionssymmetricallydisposedabouttheverticalmeridian.Theremaininghorizontallytransectedeyes,andalleyesformedwhenaleftandrightstage38eyefusedalongapposeddorsaledges,developed“double-ventralcompound”projectionstothetectum:thedorsalandventralhalvesoftheadultretinaeachprojectedtotheentiretectum,andeachtectallocuswasdrivenfromtwostimuluspositionssymmetricallydisposedaboutthehorizontalmeridian.Theresultsareconsideredintermsof(1)thekindsofcellularprocessesthatcouldmediatetheobservedmodificationsintheoriginaldevelopmentalprogram;(2)thenatureandstabilityoftheprogram;and(3)thegeneralsuitabilityofeyefragment-fusionexperimentsforanalysisoftheassemblyofretinotectalconnections.

[学科分类] 生物科学（综合）