. Thelong-termobjectiveofthisstudyistounderstandsignalsnormallyinvolvedindevelopmentoftheaxial skeletonsothattherapiesthatmimicnormaldevelopmentcanbeappliedtothespine.MembersoftheTgfb superfamilyaresecretedsignalingproteinsthatregulatemanyaspectsofskeletaldevelopmentand maintenance.PolymorphismsandmutationsingenesthatregulateTgfbactivityhavebeenassociatedwith pathologyinthespine.Previously,weandothersshowedusinggeneticallyengineeredmiceandcellculture modelsthatTgfbr2isrequiredfordevelopmentandmaintenanceofthefibroustissuesinthespine:the annulusfibrosusoftheintervertebraldisc,ligaments,andtendon.Resultsobtainedduringthepreviousfunding periodsindicatethatTgfbregulatescellfatedecisionsinthesclerotome,theprogenitoroftheconnective tissuesinthespine.BasedonpublishedliteratureandpreliminarydataweproposedthatTgfbfavorsthe formationoffibrouscelltypeswhileBMPfavorschondrogenesisandformationofthevertebralbodies.Inthis applicationweproposetoaddresstheinstructivemechanismswherebyTgfbregulatesformationand maintenanceoffibroustissuesinthespine.Inaddition,weproposetoaddresstheproblemofsclerotome resegmentationduringdevelopmentoftheaxialskeleton.Resegmentationisaprocessthatcreatesthespatial organizationoftissuesinthespinethatallowmotion.Alterationsinresegmentationwouldbeexpectedtoalter thecontextinwhichcellsdifferentiate,affectingpermissivesignalsandcompetencetorespondtoinstructive signalsthatgovernpair-wisecellfatedecisions.Finally,usingamousemodelandTGF-loadedscaffolds, bothdevelopedinthelastfundingperiod,wewilldeterminetheroleandeffectsofTGF-onmechanically induceddiscdegeneration.Specifichypothesesbasedonpublishedresultsandpreliminarydatawillbetested: 1)Tgfbactsthroughanon-canonicalsignalingpathwayinvolvingErktoregulateScxmRNAexpressionand thenthroughcooperationofScxandSmad3proteinstoregulatefibrousdifferentiationinthespine;?2)Tgfb regulatesresegmentationofsclerotome;?and3)TGF-protectsand/orrepairsfibroustissuessubjectedto mechanicallyinduceddegeneration.Theexperimentsdescribedherewilladdressquestionsabout developmentintheaxialskeletonandprovideinformationnecessaryforfutureeffortstoengineertherapiesfor thespine.
. Theexperimentsdescribedherewilladdressbasicmechanismsofdevelopmentintheaxialskeletonand provideinformationnecessaryforfutureeffortstodevelopmentallyengineerfibroustissuesofthespine, providingrelieftothosesufferingfromdegenerativedisease.
