细胞生物学 第22讲细胞分化和死亡

Cellsincreasetheirnumberbycelldivision.Howdotheyincreasetheirtypes?Howdotheybecomeanothertypebychangingtheirstructuresandfunctions?1Embryonicdevelopment2Totalcellnumber：1014Totalcelltypes：>200Embryonicdevelopment3AfertilizedeggcellAnentireorganismDifferentiation

CellDifferentiationTheprocessbywhichalessspecializedcellbecomesamorespecializedcelltype.(Tobecomedifferentinmorphology,biochemistryandfunction)Cellsincreasetheirtypebycelldifferentiation.5ThedifferentcelltypesofamulticellularorganismcontainthesameDNA(wholegenome)6DifferentiatedcellscontainthesameDNAandallthegeneticinstructionsnecessarytodirecttheformationofacompleteorganism7DifferentiatedcellscontainthesameDNAandallthegeneticinstructionsnecessarytodirecttheformationofacompleteorganismAskincellAnorganismQ?AdifferentiatedcellUndifferentiatedcellDifferentiatedcells?8DifferentiatedcellscontainthesameDNAandallthegeneticinstructionsnecessarytodirecttheformationofacompleteorganismAnysinglecellAnentireorganism(plant)Dedifferentiation9DifferentiatedcellscontainthesameDNAandallthegeneticinstructionsnecessarytodirecttheformationofacompleteorganismAnysinglecellAnentireorganism(mammal)Clonesofoneanother,GeneticallyidenticalDedifferentiation10TheNobelPrizeinPhysiologyorMedicine2012JohnB.Gurdon

eliminatedthenucleusofafrogeggcellandreplaceditwiththenucleusfromaspecialisedcelltakenfromatadpoleThemodifiedeggdevelopedintoanormaltadpole.Subsequentnucleartransferexperimentshavegeneratedclonedmammals.11Cloninganimals:

sheepDolly(1997)Andothers12TheNobelPrizeinPhysiologyorMedicine2012JohnB.Gurdon：

Becausethenucleusofdifferentiatedcellremainspluripotency.Q?AdifferentiatedcellUndifferentiatedcellDifferentiatedcells?13De-differentiationandTrans-differentiationDe-differentiation:AreverseofthestateofdifferentiationTrans-differentiationAshiftofthestateofdifferentiationDe-differentiationorTrans-differentiation14Cellpotencyisageneraltermwhichdescribesastemcell'sabilitytodifferentiateintodifferentcelltypes.Themorecelltypesastemcellcandifferentiateinto,thegreateritspotency.15Totipotentcells:zygoteandmorulacellsTotipotency

istheabilityofasinglecelltodivideandproduceallofthedifferentiatedcellsinanorganism.Inthespectrumofcellpotency,totipotencyrepresentsthecellwiththegreatestdifferentiationpotential.ToticomesfromtheLatintotuswhichmeans"entirely."16pluripotency：pluripotency(pluricomesfromtheLatinplurimus,meaningverymany)referstoastemcellthathasthepotentialtodifferentiateintoanyofthethreegermlayers:endoderm(interiorstomachlining,gastrointestinaltract,thelungs),mesoderm(muscle,bone,blood,urogenital),orectoderm(epidermaltissuesandnervoussystem).unipotency：Onestemcellhasthecapacitytodifferentiateintoonlyonecelltype.potency：

totipluri(multioligo)uni17Stemcell:relativelyundifferentiatedcellsStemcellsarebiologicalcellsfoundinallmulticellularorganisms,thatcandivide(throughmitosis)anddifferentiateintodiversespecializedcelltypes,andcanself-renewtoproducemorestemcells.Inmammals,therearetwobroadtypesofstemcells:embryonicstemcells,whichareisolatedfromtheinnercellmassofblastocysts,andadultstemcells,whicharefoundinvarioustissues.18Stemcell:relativelyundifferentiatedcellsInmammals,therearetwobroadtypesofstemcells:

embryonicstemcells,whichareisolatedfromtheinnercellmassofblastocysts,and

adultstemcells,whicharefoundinvarioustissues.19Whendoourcellsdifferentiate?Development(embryonicandpostnatal)TissuehomeostasisWoundhealinganimationStemcellsinsmallintestineMolCellBiol.2013Sep;33(17):3505–3514.

20

unipotent：thebasalcellsinepidermis

pluripotent:

hematopoieticstemcellsAdultstemcells21分化程度高低Epidermalcelldifferentiation22Hematopoieticcelldifferentiation23Q？Whatcontrolcelldifferentiation?(inflyegg)24Genesthatcontrolcelldifferentiationinflyegg25ChristianeNüsslein-VolhardTheNobelPrizeinPhysiologyorMedicine199526Changeofthestateofdifferentiationbyexpressingexogenousgenes27ChangeofthestateofdifferentiationbyexpressingexogenousgenesAfibroblastbecomesamusclecellafterbeingintroducedwithagene28TheNobelPrizeinPhysiologyorMedicine2012ShinyaYamanakastudiedgenesthatareimportantforstemcellfunction.Whenhetransferredfoursuchgenesintocellstakenfromtheskintheywerereprogrammedintopluripotentstemcells(3)thatcoulddevelopintoallcelltypesofanadultmouse.Henamedthesecellsinducedpluripotentstem(iPS)cells.诱导性多能干细胞

29TheNobelPrizeinPhysiologyorMedicine2012ShinyaYamanaka：

Becausethenucleusofdifferentiatedcellcanbereprogrammedbycertainsetofkeyregulators(Yamanakafactors)

Q?AdifferentiatedcellUndifferentiatedcellDifferentiatedcells?30Differentiationresultsfromdifferentialexpressionofluxurygenes31ThedifferentcelltypesofamulticellularorganismcontainthesameDNA(wholegenome),butexpressdifferent(luxury)genes!32Positivefeedbackloopmakesusdifferent!Q？Howdoonedifferentcellsbecomemore?33DNAmethylationisinheritable34ThepatternsofDNAmethylationcanbetransferredtodaughtercells35DNAmethylationandhistonmodificationsregulategeneexpressionprofilethroughchromatinstructureGenesilencing36Specificgeneexpressionprofilesdecidedifferentiation37Cellproliferationvsdifferentiation38TherapeuticcloningYamanakafactors3940全反式维甲酸诱导细胞分化用于白血病治疗上海第二医科大学1995年Leukemia.

1995

Feb;9(2):302-9.Effectof

retinoic

acid

isomersonproliferation,differentiationandPMLrelocalizationintheAPLcelllineNB4.ZhuJ,

ShiXG,

ChuHY,

TongJH,

WangZY,

NaoeT,

WaxmanS,

ChenSJ,

ChenZ.Blood.

2008Mar1;111(5):2505-15.Acutepromyelocyticleukemia:fromhighlyfataltohighlycurable.WangZY1,

ChenZ.41Blood.

2008Mar1;111(5):2505-15Induceddifferentiation42CellDeathNodeathwithoutlife43Celldeathinculturedishes

observedbyEM

细胞坏死necrosis细胞凋亡apoptosis44细胞死亡

(Celldeath)

Twotypesofcelldeath：

apoptosisandnecroptosis

细胞凋亡（apoptosis):细胞在一定的生理和病理条件下，遵循自身的程序，自己结束生命的过程。suicide细胞坏死(necrosis):外来致病因素作用下使得细胞正常代谢活动被强行中断而引起的“意外”的、被动性死亡过程；只见于病理情况下。murdertextbook??45Apoptosis:celldiesquicklyandcleanly(comparedwithnecrosis)IncellcultureInadevelopingtissueAnapoptoticcellisengulfedbyaphagocyticcellnecrosisapoptosis46ApoptosisAformofprogrammedcelldeathbywhichthemulticellularorganismseliminateunwantedcells.Themostcommonformofprogrammedcelldeath.“Apoptosis”:aGreekwordmeaning“fallingoff”,asleavesfallfromatree47Thebiologicalsignificancesofapoptosis1.Development

(embryo,postnatal)2.Tissuehomeostasis(epithelia,blood,immune)3.Damagerepair4.Senescence

Toeliminatesenescentcellstoreducetheriskofcancerdevelopment

48EmbryonicandadultdevelopmentMousepaw:apoptosissculptsthedigits(similarprocessesinourfingersandtoes)Tadpoletail:apoptosismakesfrogOnedaylater492002年因对细胞凋亡研究的杰出贡献获得诺贝尔奖50秀丽线虫51Thefirstdivisionoftwooftheventralcordneuroblasts,viewedbyNomarskiopticsinalivinganimal.Celllineagesoftheventralcord.[SulstonandHorvitz,1977]由此得出结论：线虫发育过程中共产生过1090个细胞，131个细胞通过凋亡被除去.留存959个细胞。52Q？Whatcontrolapoptosis?(inworm)ced-9:Bcl-2familymember53Organdevelopment：Thymus

normalthymusThymuswithtreatmentArrowsindicateapoptoticcells(cellshrinkage,nucleus/chromatincondensationandbudding,theapoptoticbody)LMTEMTEMApoptoticbodyMacrophageengulfingtheapoptoticbodies54Cellsdecreasetheirnumberbyapoptosis.Morethanhalfofthenervecellsproducednormallydiesoonaftertheyareproduced!Organdevelopment：Nerve

55

Twopathwaysforapoptosis（1）deathreceptor（2）mitochondrionQ？Whattriggersapoptosis(signalandsignalingpathway)?5657Coremolecularmachineryofapoptosis:Caspase

(Cysteine-containingAspartateSpecificProtease)Procaspase(inactivatedcaspase)Activatedcaspase58upstreamcaspase(initiativecaspase)downstreamcaspase(executivecaspase)substratesCaspasecascade

59Activatingplatformforprocaspase9

–workofWangXiaodong60Especiallyinimmunecells61死亡受体（外源性途径）免疫细胞死亡受体被细胞外配体结合而活化，其胞内结构域组装起死亡诱导信号复合物，激活上游胱冬肽酶（caspase8），后者激活下游胱冬肽酶（caspase3）62线粒体（内源性途径）UV,radiation,drugs,DNAdamage,hypoxia,ERstress线粒体PT孔开放，蛋白细胞色素c释放入细胞质基质，其与Apaf-1和上游胱冬肽酶（caspase9）组装起复合物，激活上游胱冬肽酶（caspase9），后者激活下游胱冬肽酶（caspase3）任何细胞63线粒体（内源性途径）操控线粒体PT孔的开放可以调控细胞凋亡的发生。关键蛋白：Bcl2家族抗凋亡成员：BCl-2,Bcl-XL…促凋亡成员：Bax,Bax,Bid…64TheconvergenceofDeathreceptor(extrinsic)pathwayandMitochondrial(intrinsic)pathway65Survivalvsapoptosis：Cellsrequiresurvivalsignalstoavoidapoptosis66Growthfactorsignaling:toliveordieApoptoticcell?viamitochondrialpathway（animation）67Observeapoptosisintissues

pancreasMyocardiumofmousetreatedwithephedrine(25mg/kg)andcaffeine(30mg/kg).ThymusofrattreatedwithdexamethasoneArrowsindicateapoptoticcells(cellshrinkage,nucleus/chromatincondensation)ToxicolPathol.2007;35(4):495–51668三氧化二砷诱导细胞凋亡用于白血病治疗上海第二医科大学1996年Blood.

1996Aug1;88(3):1052-