分子生物学教学课件：CHAPTER 19 Gene Regulation during Development

1、发育生物学是发育生物学是近年来进展最快的学科之一nNature 及其分支杂志在1994年1月2004 年8月期间刊登了1200多篇发育方面的论文。 nScience 1994年1月2004年8月期间刊登了1050多篇发育方面的论文。n在Pubmed上可以检索到46.8万篇发育相关的论文。Developmental biology is at the core of all biology.It deals with the process by which the genes in thefertilized egg control cell behavior in the embryo an

2、dso determine its pattern, its form, and much of itsbehavior. The progress in developmental biology inrecent years with the applications of advances in celland molecular biology, has been remarkable and anenormous amount of information is now available.n张红卫等主编，发育生物学， 2001。n樊启昶等主编，发育生物学原理， 2002。n桂建芳等

3、主编，发育生物学， 2002 。nLewis Wolpert， Principles of Development, Second edition，2002。nScott F Gilbert，Developmental Biology, Seventh edition，2003。主要参考教材刊登发育方面论文的主要杂志刊登发育方面论文的主要杂志nGenes and Development，nDevelopmental Cell，nDevelopment,nDevelopmental Biology,nMechnisms of Development,nAnnual Reviews of Cell

4、 and Developmental Biology,nCurrent Opinion in Genetics and Development.发育生物学的研究对象发育生物学的研究对象n发育生物学（developmental biology）是应用现代生物学的技术研究生物发育本质的科学，主要研究多细胞生物体从生殖细胞的发生、受精、胚胎发育、生长、衰老和死亡即生物个体发育（ontogeny）中生命过程发展的机制。同时，发育生物学也研究生物种群系统发生（systematics development）的机制。n与传统的胚胎学（embryology）不同，发育生物学是在20世纪50年代以后，由于分子

5、生物学、细胞生物学、遗传学以及生物化学等其他生命学科的发展，并与胚胎学的相互渗透，才逐渐发展和形成的一门新兴的生命科学。n传统的胚胎学是研究从动物受精到出生之间有机体的发育，即胚胎发育。但有机体的发育在出生后并未停止，甚至大多数成年生物体也依然继续发育。随着生长的进行，人类胚胎在大小和形态上都发生显著的变化。人类身体各部分生长的速度并不相同，九周以后身体其他部位的生长速度超过了头部。一些动物能够再生出失去的器官。一种蜥蜴（South eastern five-lined skink,东南五线石龙子）在防御中丢弃自己的尾巴。 有尾两栖类蝾螈晶状体的再生n发育生物学的形成和发展本身是多学科相互渗透

6、的结果，代表了现代生命科学的结晶。n发育生物学既是重要的基础生命科学，其研究成果又具有广阔的应用前景，已经成为当代最活跃的生命科学研究领域之一。发育生物学研究的主要任务发育生物学研究的主要任务n个体发育的基础是细胞分化（cell different-iation）。从个体发育的角度来说，一个单细胞受精卵如何通过一系列的细胞分裂和细胞分化，产生有机体内所有形态和功能不同的细胞，这些细胞之间又如何通过细胞之间的相互作用共同构建各种组织和器官，建成一个有机体并完成各种发育过程，这些都是发育生物学的主要任务。n从另一个角度来讲，发育是遗传信息按一定的时间和空间顺序表达的结果。发育具有严格的次序性，发育

7、并不是个别基因的表达，而是众多基因表达在时间和空间上的联系和配合。n发育生物学的主要任务是研究生物体发育的遗传程序及其调控机制。Chapter 19by which Cells Are Instructed to Express Specific Sets of Genes during DevelopmentuExamples of the Three StrategiesuThe Molecular Biology of Drosophila EmbryogenesismRNA serve as a critical regulatory moleculeThey are transpor

8、ted along elements of the cytoskeleton which have intrinsic polarityThe transportation is realized by an “adapter protein”“Adapter” proteinsContaining two domainspOne recognizing the 3 UTR of the mRNApThe other associates with the components of the cytoskeletonThereby it crawls along the actin filam

9、entnThree steps:1.The synthesized signaling molecules are deposited in the membrane or secreted into the extracellular matrix.2.They are recognized by the receptor on the surface of recipient cells3.The changes in gene expression in the recipient cell is achieved through the signal transduction path

10、waysb.Activated receptor cause the release of DNA-binding protein so it can enter the nucleus, regulate gene transcription.c.The intracytoplasmic domain of the activated receptor is cleaved to enter the nucleus and interact with DNA-binding protein.Gradient of Secreted Signaling Molecules Two concep

11、ts:nPositional information: a cells development is influenced by its location within the developing embryo.nMorphogens(成形素，形态发生素成形素，形态发生素) signaling molecules that control position informationb.Cells located near the source of morphogen receive high concentration of the signaling molecule, experienc

12、e peak activation of receptorsc. determine most regulatory protein enter the nucleus;d. The different levels of the regulatory factor lead to the expression of different sets of gene.1.The Localized Ash1 Repressor Controls Mating Type in Yeast by Silencing the HO gene2.A Localized mRNA Initiates Mus

13、cle Differentiation in the Sea Squirt Embryo3.Cell-to-Cell Contact Elicits Differential Gene Expression in the Sporulating Bacterium4.A Skin-Nerve Regulatory Switch Is Controlled by Notch Signaling in the Insect CNS5.A Gradient of the Sonic Hedgehog Morphogen Controls the Formation of Different Neur

14、ons in the Vertebrate Neural Tube1.mRNA localization2.Cell-to-cell contact3.Signaling through the diffusion of secreted signaling molecules1. The Localized Ash1 Repressor Controls Mating Type in Yeast by Silencing the HO geneYeast lifecycle1.Budding 2.Conjugation 3.Spore alter the nucleosomeActive o

15、nly at correct stage of cell cycle1. Mating Type in Yeast by Silencing the HO genenA haploid yeast cell budding to produce a mother cell and a smaller daughter cell.nThe daughter cell cant switch due to localized Ash1 repressor, it cant express HO which initiate switching.nThe mother cell can switch

16、: it lacks Ash1,and is able to express HO.2.A Localized mRNA initiates Muscle Differentiation in the Sea Squirt EmbryonMacho-1 mRNA is ninitially distributed nthroughout the cytoplasm of unfertilized eggs but becomes localized to the vegetal(bottom)region shortly after fertilization, ultimately inhe

17、rited by two cells of the eight-cell embryos,thus the two cells go on to form the tail muscles.3. Cell-to-Cell Contact Elicit Differential Gene Expression in the Sporulating Bacterium, B. subtilis1.1.芽孢形成过程芽孢形成过程 2.2.形成过程中基因活性的调控形成过程中基因活性的调控: : 特异特异亚基控制基因组活性亚基控制基因组活性 a. SpoOA 对外界刺激产生应答对外界刺激产生应答决定芽孢是

18、否决定芽孢是否/何时形成何时形成 b.前孢子和母细胞中的前孢子和母细胞中的亚基级联亚基级联时间依赖的变化时间依赖的变化 c. 细胞细胞-细胞间的信号传导：细胞间的信号传导： 位于隔上的受体位于隔上的受体前孢子和母细胞中事件的协调前孢子和母细胞中事件的协调 3. Cell-to-Cell Contact Elicit Differential Gene Expression in the Sporulating Bacterium, B.subtilisA A 和和H H亚基亚基E E 和和F F亚基亚基Figure 12.20 Role of SpoOA in Bacilius sporula

19、tion激活激活E E 和和F F 的表达基因的表达基因 A A：F F 激活激活结果：结果： E E 是母细胞特异的是母细胞特异的 F F 是前孢子特异的是前孢子特异的前孢子中的前孢子中的F F 和和母细胞中母细胞中E E 被激活被激活亚基级联亚基级联F F G G ：识别芽孢分化后期识别芽孢分化后期要转录的基因（要转录的基因（SpoBSpoB）SpoFSpoF K K： 指导母细胞后期指导母细胞后期要转录的基因要转录的基因4.Delta-Notch Signaling control skin-nerve regulatory in the Insect CNSnIn all verteb

20、rate embryos, there is a stage when cells located along the dorsal ectoderm move toward internal regions of the embryo and form the neural tube.nCells located in the ventral most region of the neutral tube form floorplate, where the secreted signaling molecule Sonic Hedgehog(Shh) is expressed. Shh f

21、unctions as a gradient morphogen. by which Cells Are Instructed to Express Specific Sets of Genes during DevelopmentuExamples of the Three StrategiesuThe Molecular Biology of Drosophila Embryogenesispositional informationThe Molecular Biology of Drosophila EmbryogenesisOocyte n. 卵母细胞卵母细胞 metamorphos

22、is n.变形变形Larval adj.幼虫的幼虫的 Larva n.幼虫幼虫 pupa n.昆昆蛹蛹Molt n. 换毛期换毛期 Thorax n. 胸腔胸腔An Overview of Drosophila EmbryogenesisThe Molecular Biology of Drosophila EmbryogenesisOocyte n. 卵母细胞卵母细胞 metamorphosis n.变形变形Larval adj.幼虫的幼虫的 Larva n.幼虫幼虫 pupa n.昆昆蛹蛹Molt n. 换毛期换毛期 Thorax n. 胸腔胸腔A Morphogen Gradient C

23、ontrols Dorsal-Ventral Patterning of the Drosophila EmbryonAfter fertilization, Sptzle binds to the cell surface Toll receptor.Depending on the concentration of Sptzle, Toll is activated to greater or lesser extent.Peak activation of Toll is in ventral regions, where the Sptzle concentration is high

24、est.nToll signaling causes the degration of a cytoplasmic inhibitor Cactus, and the release of Dorsal from the cytoplasm into nuclei.nThe Dorsal gradient specifies three major thresholds of gene expression across the dorsal-ventral axis of embryos undergoing cellularization.twist generhomboid geneso

25、g genetwistSegmentation Is Initiated by Localized RNAs at the Anterior and Posterior Poles of the Unfertilized Eggbicoidoskar The Bicoid Gradient Regulates the Expression of Segmentation Genes in a Concentration-Dependent FashionnOnly high concentrations of Bicoid activate the expression of orthoden

26、ticle, while both high and intermediate concentrations are sufficient to activate hunchback.nThis differential regulation of orthodenticle and hunchback depends on the binding affinities of Biciod recognition. nThe Bicoid protein binds to DNA as a monomer, Bicoid monomers interact with each other to

27、 foster the cooperative occupancy of adjacent sites.Hunchback Expression Is also Regulated at the level of TranslationThis dual regulation of hunchback expression produces a steep Hunchback protein gradient with the highest concentrations located in the anterior half of the embryo and sharply diminishing levels in the posterior half.The Gradient of Hunchback Repressor Establishes Different Limits of Gap Gene ExpressionHunchback and Gap proteins produce Segmentation Stripes of Gene ExpressionWe will consider the expression of eve stripe 2 for exam