细胞生物学198-14-1胚胎发育、分化与调控

1、1,第十三章,胚胎发育、 分化与调控,2, 个体发育(individual development) 从受精卵形成胚胎，再由胚胎生长发育成个 体的过程称为个体发育。 从形态上看，个体发育过程经历: 生长(growth)、 分化(differentiation) 形态发生(morphogenesis)。 细胞分化 细胞的后代在形态、结构和功能上发生差异的过程称为细胞分化，其本质是基因选择性表达的结果，即基因表达调控的结果。,3,细胞分化,4,13.1 配子发生与受精作用,13.1.1 配子发生(gametogenesis) Male gamete and female gamete: 动物和植物的雌配子通常称为卵 （ova或egg）； 雄配子称为精子（sperm） 配子形成的过程称为配子发生,5,Oogenesis,大多数动物的卵子发生在卵巢; 增殖期(proliferation phase) 卵原细胞(oogonia)通过有丝分裂 增加细胞数量； 经过增殖之后，卵原细胞进行减数分裂，此时的卵原细胞被称为卵母细胞(oocyte)； 经减数分裂，染色体发生遗传重组，并将染色体组的数量减半成

2、为单倍体。,6, 滤泡细胞(follicular cell) 滤泡细胞是卵母细胞周围的细胞，为卵母细 胞提供其他的物质; 抚育细胞(nurse cell) 为无脊椎动物，如昆虫的卵母细胞生长提供支持。抚育细胞与卵母细胞是由相同的细胞系产生的； 卵母细胞在发育过程中具有显著的不对称性，卵母细胞的一端称为植物极(vegetal pole),具有大量的卵黄小体和储备营养。相反的一端称为动物极(animal pole)，含有较少的储备营养，但含有细胞核、核糖体、内质网、线粒体和色素颗粒。,7,The stages of oogenesis,8,An egg is highly specialized for independent development with large nutrient reserves and an elaborate coat,9,The egg cytoplasm contains nutritional reserves in the form of yolk, which is rich in lipids, proteins, and polysacchar

3、ides and is usually contained within discrete structures called yolk granules. The egg coat is another peculiarity（特殊结构） of eggs. It is a specialized form of extracellular matrix consisting largely of glycoprotein molecules, some secreted by the egg and others deposited on it by surrounding cells. In many species, the major coat is a layer immediately surrounding the egg plasma membrane; in nonmammalian eggs, such as those of sea urchins or chickens, it is called the vitelline layer(卵黄层), wherea

4、s in mammalian eggs it is called the zona pellucidu(透明带).,10,The zona pellucida,11,Cortical granules(皮质颗粒) : Many eggs (including those of mammals) contain specialized secretory vesicles just under the plasma membrane in the outer region, or cortex, of the egg cytoplasm. When the egg is activated by a sperm, these cortical granules release their contents by exocytosis; the contents of the granules act to alter the egg coat so as to prevent more than one sperm from fusing with the egg. Cortical g

5、ranules are usually distributed evenly throughout the egg cortex, but in some organisms other cytoplasmic components have a strikingly asymmetrical distribution. Some of these localized components later serve to help establish the polarity of the embryo.,12,Spermatogenesis,支持细胞(sertoli cell) 为发育中的精子提供保护和营养 精原细胞(spermatogonium) 雄性原始生殖细胞 精母细胞(spermatocyte) 精子细胞(spermatid) 精细胞(sperm cell),13,The stages of spermatogenesis,14,Cytoplasmic bridges in developing sperm cells and their precursors,15,13.1.

6、2 fertillization,Once released, egg and sperm alike are destined to die within minutes or hours unless they find each other and fuse in the process of fertilization. Through fertilization, the egg and sperm are saved: the egg is activated to begin its developmental program, and the haploid nuclei of the two gametes come together to form the genome of a new diploid organism. 顶体反应(acrosomal reaction) 皮层反应(cortical reaction) 原核融合(pronuclei fusion),16,The acrosome reaction that occurs when a mammali

7、an sperm fertilizes an egg,17,The egg cortical reaction helps to ensure that only one sperm fertilizes the egg,多精受精（polyspermy） If more than one sperm fuses-a condition called polyspermy-multipolar or extra mitotic spindles are formed, resulting in faulty segregation of chromosomes during cell division; nondiploid cells are produced, and development usually stops. 有两种机制防止多精受精： primary block to polyspermy secondary block to polyspermy,18,How the cortical reaction in a mouse egg is thought to prev

8、ent additional sperm from entering the egg,19,The coming together of the sperm and egg pronuclei after mammalian fertilization,20,受精激活与母体效应,蛋白质合成 精卵细胞质膜 融合后即开始 母体信息 蛋白质 mRNA 调控因子被激活 激活机理信号转导,21,13.2 多细胞生物的发育,The four essential processes by which a multicellular organism is made: cell proliferation, cell specialization, cell interaction, and cell movement.,22,13.2.1 UNIVERSAL MECHANISMS OF ANIMAL DEVELOPMENT,Animals share some basic anatomical features Cleaves, to form many smaller cells Ectoderm

9、-the precursor of the epidermis and of the nervous system. Endoderm-the precursor of the gut and its appendages, such as lung and liver. Another group of cells move into the space between ectoderm and endoderm, Mesoderm-the precursor of muscles, connective tissues, and various other components. This transformation of a simple ball or hollow sphere of cells into a structure with a gut is called gastrulation,23,受精卵的卵裂,24,原肠胚(gastrula)形成,胚孔(blastopore) 原肠胚(gastrula) 由3层细胞层构成的： 外胚层(ectoderm) 中胚层(mesoderm) 内胚层(endoderm),25,Gastrulation(原肠胚形成),26,Manipulation of the embryo reveals the interactions between its cells,A cell lineage tracing experiment in the Xenopus embryo. Different fluorescent dyes are injected into three cells at an early stage (cells with asterisks at the 32-cell stage), and the embryo is then left to develop for 10 hours before being fixed and sectioned. The pattern of fluorescent labeling revea

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