1、l Cells increase their number by cell division.l How do they increase their types?l How do they become another type by changing their structures and functions?Total cell number：1014 Total cell types：200 Embryonic development The process by which a less specialized cell becomes a more specialized cel
2、l type. (To become different in morphology, biochemistry and function)l Cells increase their type by cell differentiation.The different cell types of a multicellular organism contain the same DNA (whole genome)Differentiated cells contain the same DNA and all the genetic instructions necessary to di
3、rect the formation of a complete organismA skin cell An organism Q? A differentiated cell Undifferentiated cell Differentiated cells?Differentiated cells contain the same DNA and all the genetic instructions necessary to direct the formation of a complete organismAny single cell An entire organism (
4、plant)DedifferentiationDifferentiated cells contain the same DNA and all the genetic instructions necessary to direct the formation of a complete organismAny single cell An entire organism (mammal)Clones of one another,Genetically identicalDedifferentiationCloning animals: sheep Dolly (1997)And othe
5、rs De-differentiation and Trans-differentiation De-differentiation: A reverse of the state of differentiation Trans-differentiationA shift of the state of differentiationDe-differentiation or Trans-differentiationlCell potency is a general term which describes a stem cells ability to differentiate i
6、nto different cell types.lThe more cell types a stem cell can differentiate into, the greater its potency. Totipotency is the ability of a single cell to divide and produce all of the differentiated cells in an organism.In the spectrum of cell potency, totipotency represents the cell with the greate
7、st differentiation potential. Toti comes from the Latin totus which means entirely.pluripotency：pluripotency (pluri comes from the Latin plurimus, meaning very many) refers to a stem cell that has the potential to differentiate into any of the three germ layers: endoderm (interior stomach lining, ga
8、strointestinal tract, the lungs), mesoderm (muscle, bone, blood, urogenital), or ectoderm (epidermal tissues and nervous system).unipotency：One stem cell has the capacity to differentiate into only one cell type. potency ： toti pluri (multi oligo) uniStem cell: relatively undifferentiated cellsStem
9、cells are biological cells found in all multicellular organisms, that can divide (through mitosis) and differentiate into diverse specialized cell types, and can self-renew to produce more stem cells. In mammals, there are two broad types of stem cells: embryonic stem cells, which are isolated from
10、the inner cell mass of blastocysts, and adult stem cells, which are found in various tissues. When do our cells differentiate ?l Development (embryonic and postnatal )l Tissue homeostasisl Wound healinganimation unipotent：the basal cells in epidermis pluripotent: hematopoietic stem cells Adult stem
11、cells表皮干细胞的分化表皮干细胞的分化造造血血干干细细胞胞的的分分化化 活体肝移植供者的肝脏组织在移植后的体积和功能恢复 2009年“暴走母亲”捐肝救子Cell differentiation vs wound healingQ？What control cell differentiation? (in fly egg)Genes that control cell differentiation in fly eggChristiane Nsslein-VolhardChange of the state of differentiation by expressing exogeno
12、us genesChange of the state of differentiation by expressing exogenous genesPositive feedback loop makes us different!Q？How do one different cells become more?DNA methylation is inheritableThe patterns of DNA methylation can be transferred to daughter cellsSpecific gene expression profiles decide di
13、fferentiationG G0 0期细胞期细胞分化相细胞分化相细胞Cell proliferation vs differentiationTherapeutic cloning未知：未知：干细胞向特定方向（干细胞向特定方向（lineage）诱导）诱导分化的因子及其组合分化的因子及其组合全反式维甲酸诱导细胞分化用于白血病治疗全反式维甲酸诱导细胞分化用于白血病治疗未知：未知：诱导肿瘤细胞或肿瘤干细胞重新分化诱导肿瘤细胞或肿瘤干细胞重新分化的因子及其组合的因子及其组合No death without life Apoptosis: programmed death, suicidenecros
14、is: accidental, murdered But细胞死亡细胞死亡 (Cell death) 细胞凋亡和坏死细胞凋亡和坏死 细胞死亡有两种形式：细胞死亡有两种形式：细胞凋亡和细胞坏死细胞凋亡和细胞坏死 细胞凋亡（细胞凋亡（apoptosis): apoptosis): apoptosisapoptosis为希腊语，原为希腊语，原指秋天时树叶自然凋零。细胞凋亡指细胞在一定的生指秋天时树叶自然凋零。细胞凋亡指细胞在一定的生理和病理条件下，遵循自身的程序，自己结束生命的理和病理条件下，遵循自身的程序，自己结束生命的过程。过程。 细胞坏死细胞坏死( (necrosis): necrosis):
15、外来致病因素作用下使得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细胞正常代谢活动被强行中断而引起的“意外意外”的、的、被动性死亡过程；只见于病理情况下被动性死亡过程；只见于病理情况下。 textbook 细胞坏死necrosis 细胞凋亡apoptosisThe biological significances of apoptosis 1. Development (embryo, postnatal)2. Tissue homeostasis (epithelia, blood, immune)3. Damage repair4. Senescence To eliminat
16、e senescent cells to reduce the risk of cancer development 2002年因对细胞凋亡研究的杰出贡献获得诺贝尔奖年因对细胞凋亡研究的杰出贡献获得诺贝尔奖The first division of two of the ventral cord neuroblasts, viewed by Nomarski optics in a living animal. Cell lineages of the ventral cord.Sulston and Horvitz, 1977l Cells decrease their number by
17、apoptosis. Two pathways for apoptosis（1）death receptor（2）mitochondrionActivating platform for procaspase9 work of Wang XiaodongSurvival vs apoptosis：Cells require survival signals to avoid apoptosisGrowth factor signaling: to live or die Apoptotic cell?via mitochondrial pathway（animation）三氧化二砷诱导细胞凋亡用于白血病治疗三氧化二砷诱导细胞凋亡用于白血病治疗
