细胞生物学作业.docx
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细胞生物学作业.docx
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细胞生物学作业
Foeturnedfriend:
multiplefunctionalrolesattributabletohyper-activating
stemcellfactorreceptormutantinregenerationofthehaematopoieticcell
compartment
S.Pati*,1,O.P.Kalra†andA.Mukhopadhyay*
*StemCellBiologyLaboratory,NationalInstituteofImmunology,ArunaAsafAliMarg,NewDelhi,India,and†DepartmentofMedicine,University
CollegeofMedicalSciencesandGuruTegBahadurHospital,UniversityofDelhi,NewDelhi,India
Received1June2010;revisionaccepted2July2010
Abstract
Objectives:
Stemcellfactorreceptor,c-kit,is
consideredtobethemastersignallingmoleculeof
haematopoieticstemcells.Itdevelopstheorchestral
patternofhaematopoieticcelllineages,seenbyits
varyingdegreeofomnipresenceinprogenitors,lineage
committedandmaturecells.Wehaveinvestigated
theeffectofover-expressingc-kitonearly
recoveryofthehaematopoieticcompartment,inirradiated
hosts.
Materialsandmethods:
Normalbonemarrowcells
(BMCs)weretransfectedwithKitwt(wild-typec-kit)
oritsvariantKitmu(asp814tyr)byelectroporation.
Lethallyirradiatedmiceweretransplantedwithnormal
ortransfectedcongeneicBMCs.Theeffectof
ectopicexpressionofc-kitonhaematopoieticcell
recoverywasdeterminedbyanalysingdonor-derived
cells.Furthermore,effectsofbothtypesofc-kitoverexpression
onprogenitorandlineage-committedcells
wereexaminedbyflowcytometricanalysisofSca-1
andlineage-committed(Lin+)cellsrespectively.
Results:
Hyper-activatingKitmusignificantlyimproved
recoveryofthehaematopoieticsystemin
irradiatedhosts.Invivoresultsshowedthatthe
donor-derivedc-kit+cellpopulationwasincreasedto
morethan3-foldinthecaseofKitmu-transfectedcells
comparedtonormalandKitwtover-expressing
BMCs.Ingeneral,survivalofprogenitorand
committedcellwasimprovedintheKitmu
over-expressingsystemcomparedtotheothertwo
cohorts.
Conclusion:
Theseresultssuggestthatrecruitment
ofthehyper-activatingvariantofc-kit(Kitmu)leadto
earlyrecoveryofthebonemarrowoflethally
irradiatedmice.
Introduction
Haematopoieticstemcells(HSCs)areembodiedwith
immensecapabilitytoconstructacompletehaematopoietic
compartmentfromasinglecell,whichactsastheprimitive
powerhouse(1,2).Radiation-induceddamageofthe
bonemarrow(BM)leadstomyelodysplasia,resulting
fromdeathofprogenitors,withconsequentlossoffunctional
cells.Thecurrentapproachtosuccessfulmanagement
oftreatingmalignancyincludesradiationand⁄or
chemotherapy.Thismayresultindepletionofstemcells,
organfailureandlateeffectsthatmightcontributeto
malignanttransformation(3).
Patientsundergoingradiationaregivenhaematopoietic
celltherapyfromthreemajorsources:
(i)autologous⁄allogeneic
BM,(ii)cytokinemobilizedautologousperipheral
blood,andrecently(iii)cordblood.Thesesourcesofcells
haveseverallimitationssuchasimproperHLA-matched
donorcells,requirementofimmunosuppressanttreatment,
recurrenceoftumoursandrequirementofhighdosageof
cellsfortransplantation.Theabovelimitationsareclinically
manifestedasearlyeffects(forexample,mucositis,
graft-versus-hostdisease,haemorrhagiccystitis,lung
injuryandveno-occlusivedisease)andlateeffects(for
example,musculoskeletaleffects,oculareffects,endocrine
effectsandneurocognitiveandneuropsychological
effects),thusdemandingfasterrecoveryofthehaematopoietic
system.
Correspondence:
A.Mukhopadhyay,StemCellBiologyLaboratory,
NationalInstituteofImmunology,ArunaAsafAliMarg,NewDelhi-
110067,India.Tel.:
+91-11-26703781;Fax:
+91-11-26702125;E-mail:
ashok@nii.res.in
1Presentaddress:
DepartmentofNeuroscience,SchoolofMedical
Sciences,UniversitySainsMalaysia,Malaysia.
10_2010BlackwellPublishingLtd.
CellProlif.,2011,44,10–18doi:
10.1111/j.1365-2184.2010.00713.x
Earlyrecoveryofthehaematopoieticsystemfrom
lethalirradiationisstrictlylimitedduetoG0-silenceor
quiescencenatureofHSCs.Hence,analternativestrategy
isexpectedtobebeneficialbyengineeringdormanthaematopoietic
cellsforinitiationofearlysignallingevents.
AlthoughmanyHSC-specifictranscriptionfactors,growth
factorreceptorsandcorrespondingligandsareknownto
activatehaematopoieticcells,recruitmentofamastersignalling
switchwouldensurestage-specificregenerationof
cells(4–6).
Previousstudieshaveshownthatviralvector-based
genedeliveryinHSCshasmanydrawerbacks(7–9).
PrimitiveHSCs(Lin)Sca-1+c-kit+;LSK),whichare
only0.5%oftotalBMcells,havedenselypacked
DNAinsideintactnuclearmembranes.Thisrenders
themdifficulttotransfectbyaviral-mediatedgene
transfermethod.Thesecondobstructionisseenas
post-maintenanceofthesemodifiedpopulationsinvivo
forshort-termaswellaslong-termgeneexpression,as
aresultofcompetitionbetweentransducedandnontransduced
cells.Thishasbeenshowninthecaseof
patientswithchronicgranulomatousconditionsinfused
withgp91phox-transducedpurifiedCD34+peripheral
bloodcells(7).Thethirdandmostsevereproblem
associatedwithviralgenetherapyisdevelopmentof
oncogenesisarisingfrominsertionalmutagenesis.Many
genetherapystudieshaveshowndevelopmentof
leukaemiainpatientswhohadundergonetreatmentfor
severecombinedimmunodeficiency(8,9).
Consideringtheaboveshortfallsofvirus-mediated
genetransfer,weproposeaprotocolofelectroporationmediated,
transientover-expression,ofamastersignal
transducerc-kitwtanditshyper-activatingvariant[Kitmu
(asp814tyr)]toreconstitutethehaematopoieticsystem.
Theelectroporationmethodisknowntoinduceless
celldeathascellsdonotexperiencechemicaltoxicity
asinthecaseofchemical-mediatedtransfection(10–
12).Earlierstudieshaveconfirmedc-kitwtasthekey
receptorforgrowthandsurvivalofHSCs(13,14).
Undernormalcircumstances,c-kitisactivatedbyits
ligandstemcellfactor(SCF).Inhumans,constitutive
activationofc-kitinneoplasticmastocytosishasbeen
showntobypassSCFinterferenceindownstreamsignalling
duetoclusteringofgain-of-functionmutation
Asp816toValintheKitactivationdomain(15).
Recently,wehavepredictedthatcertainactivationloop
residuesinc-kitarecrucialforinteractionofkinases
withShp-1fordestabilization.Pointmutationin
stretchesofLys818toSer821andThr847toGlu849
intheKitcatalyticdomainmayleadtogenerationofa
hyperactivevariantofc-kit(16).Inthemouse,Asp814
toTyrmutationoftheKitactivationloopresultsin
over-expressionofkinasesasbydegradationoftyrosine
phosphatase(Shp-1)(17).HyperactiveKitkinase
hasbeenreportedtobeassociatedwithconstitutive
activationofphosphoinositide-3kinase(PI3kinase),
signaltransducerandactivatoroftranscription3
(STAT3),andnuclearfactorkappaB(NF-jB)signalling
pathways[16–18].Cellsaffectedwerealsoindependent
ofSCFforgrowth(18).Theseresultssuggest
thatrecruitmentofahyper-activatingmutantlikeKitmu
(asp814tyr)wouldinfluencedownstreamsignallingin
lethallyirradiatedhoststofacilitatehaematopoiesis.
Materialsandmethods
Animals
Six-toeight-week-oldC57BL⁄6J[Ptprcb(Ly5.2)]and
BL6.SJL[Ptprcc(Ly5.1)]micewereusedinthisstudy.
MicewereobtainedfromtheJacksonLaboratory(Bar
Harbor,Maine,USA,http:
//www.jax.org)andmaintained
inourinstitute’sexperimentalanimalfacility.Duringthe
experiments,micewerekeptinanisolatorandfedautoclaved
acidifiedwaterandirradiatedfoodadlibitum.All
experimentsusingmicewereconductedaccordingtothe
proceduresapprovedbytheInstitutionalAnimalEthics
Committee.
IsolationofBMcells
BMCswereisolatedbyflushingtwotibiaandtwofemurs
from6-to8-week-oldLy5.1mice,anderythrocyteswere
lysedbytreatmentwithGey’ssolution(19).Cellsuspension
wasincubatedinatissuecultureplatefor12hto
removeadheredstromalcells.Priortoelectroporation,
non-adherentviablecellswerecountedusingthetrypan
bluedyeexclusionmethod.
ElectroporationofBMcells
BMCswereculturedfor12hat37_CinaCO2incubator.
Electroporationofcells(10・106percuvette)wasperformed
usingaGenePulserIIBioradelectroporator(Hercules,
CA,USA)at1.7kV⁄cmcurrentand400lspulse
length.Acustom-mademinipulsechamber(withcapacity
ofhighcelldensity)havingrectangularstainlesssteel
electrodes(4mm)wasusedforelectroporation.Polyethylene
glycol-purifiedpcDNA3.1-Kitconstructswere
dilutedinelectroporationbuffer[10mMHEPES,IMDM
supplementedwith5%FCSand5%FBS]ataconcentration
of50–100lgDNA⁄ml.Toavoidpost-pulseapoptosis,
electroporatedcellswerewashedandincubatedat
37_Cinthe5%CO2incubatorfor15min.Incubationof
post-pulsedcellsisbelievedtofacilitateresealingofpores
(10,11).
_2010BlackwellPublishingLtd,CellProliferation,44,10–18.
Haematopoieticrecoverybyhyper-activatingc-kit11
CultureofLy5.1BMCs
ElectroporatedcellswereculturedinIscove’smodified
Dulbecco’smedium(IMDM),supplementedwith10%
FCS,50ng⁄mlmurineSCFand10ng⁄mlinterleukin-3
(IL-3)(PeproTechAsia,Rehovot,Israel,http:
//www.
).Cellswereculturedfordifferenttimesat
37_Cina5%CO2incubatorandviablecellnumberwas
determined.
Flowcytometry
Cellswerelabelledwithantibodiesandanalysedaccording
tomethodsdescribedinourpreviousstudy(20).
Antibodiesusedherewereanti-:
Sca-1⁄FITC,c-kit⁄
phycoerythrin-Cy5(BDPharmingen,SanJose,CA,
USA),CD45.1⁄PE-Cy5andCD16⁄32(eBiosciences,San
Diego,CA,USA).Lineagea
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