BackgroundInformation | TUC(TOAD[TurnedOnAfterDivision]/Ulip/CRMP)isafamilyofproteinsthathaveemergedasstrongcandidatesforaroleinneuronalgrowthconesignaling.TheTUC-4familymembersreachtheirhighestexpressionlevelsinearlypost-mitoticneuronsduringtheirpeakperiodsofaxonalgrowth.TUC-4isnotexpressedinneuralProgenitorsoradultneurons(withminorexception).DatasuggeststhatTUC-4playsaroleinaxonaloutgrowth,pathfindingandpossIBLyintheprocessthatpermitsgrowingaxonstochooseproperroutesandtargets(Quinn,1999).TheTUC-4proteinisexpressedprimarilywithinthecytoplasmofpostmitoticneuronsastheybegintheirmigrationoutoftheventricularzoneintothedevelopingcorticalplate(Minturn,1995a).TUC-4isexpressedinneuronalcellbodies,neurites,andalongthemostdistalregionsofneuronalgrowthcones,includingthelamellipodiaandfilopodia(Minturn,1995b).ExpressionofTUC-4isobservedbydayE12inratscoincidentwiththeexpressionoftheearlyneuronalMarkerclassIIIbeta-tubulin(Quinn,1999).TUC-4expressionisrarelyobservedinneuronalcellsexpressingthemitoticmarkerPCNA(Minturn,1995a).TheexpressionofTUC-4hasbeenshowntobeupregulatedinresponsetoNGFinrats(Minturn,1995b)andinresponsetoretinoicacidinahumanneuroblastomacellline(SMS-KCNR;Gaetano,1997). |