哺乳动物线粒体遗传和在体细胞克隆胚胎中的命运

线粒体是哺乳动物重要的细胞器之一,为细胞的生命活动提供能量.线粒体是除细胞核外唯一含有功能性基因组DNA的细胞器.由于线粒体在哺乳动物早期胚胎的发育中有多方面重要的作用,因此线粒体对体细胞克隆胚胎发育的影响成为体细胞克隆动物研究的热点.就线粒体的结构特点和遗传特性及其在同种、异种动物克隆早期胚胎发育过程中的命运以及可能的遗传机制进行综述.同时,也将比较注射异源线粒体后,线粒体在注射胚胎中的发育命运.     

核移植与线粒体

线粒体是哺乳动物的产能、供能细胞器,与生长、发育、衰老和凋亡等多种细胞事件及疾病有关。哺乳动物核移植可能导致克隆胚胎及后代中线粒体的杂合性,从而影响到个体的表型甚至导致线粒体疾病。文章阐明了哺乳动物中线粒体的生物学功能及遗传特性,并分析了核移植中供体细胞和受体卵胞质两种来源的线粒体在同种胚胎细胞核移植、同种及异种体细胞核移植重构胚发育进程中的变化以及可能影响线粒体杂合性的一些因素,对其可能导致的线粒体疾病及解决方法进行了简单的阐述。

     

亲环蛋白D和线粒体相关的细胞坏死

线粒体是细胞内一种重要的细胞器,与许多细胞生理过程密切相关,最新研究表明,线粒体通透性转变孔的一个成员亲环蛋白D与细胞坏死有着紧密联系,线粒体通过亲环蛋白D调节的通透性转换而决定着细胞的命运,从而使我们对线粒体和亲环蛋白D的功能有了更为全面的认识。     

哺乳动物核移植中线粒体命运

线粒体是哺乳动物细胞中一种重要的产能、供能细胞器,与生长、发育、衰老和凋亡等多种细胞事件以及多种疾病有关.哺乳动物核移植中,供体细胞和受体卵胞质两种来源的线粒体在重构胚胎发育进程中的变化一直是科学家们研究的热点.对哺乳动物同种胚胎细胞核移植、同种体细胞核移植、异种核移植研究中线粒体的变化进行了综述.     

线粒体DNA靶向治疗

线粒体(mitochondrion)是真核生物细胞中的一种非常重要的细胞器,含有独立于细胞核染色体外的遗传物质,通过氧化磷酸化产生ATP,是细胞的能量工厂,与细胞分化、信号转导、代谢稳态等过程密切联系。线粒体功能的紊乱与癌症、神经退行性疾病、糖尿病等许多疾病的发生、发展及治疗息息相关。线粒体在细胞命运中扮演的关键角色,使对线粒体这一特殊细胞器的探索成为生命科学研究热点之一。人线粒体DNA(mitochondrial DNA, mtDNA)是一相对保守且仅16 kb的环状双链DNA分子,只含37个基因,但这些基因都是维持线粒体功能稳定必不可少的部分。随着对线粒体功能认识的不断深入,研究人员发现mtDNA突变,会导致活性氧自由基过量产生,从而引起细胞衰老,甚至引发诸多疾病,例如遗传性视神经病变、线粒体脑肌病伴高乳酸血症和卒中样发作综合征等。但是,目前针对这些线粒体基因疾病尚无非常有效的治疗手段。为了进一步了解这一关键细胞器,研究人员开发了一些有效的方法来突破线粒体的复杂屏障。本文将重点介绍并讨论近几年靶向mtDNA的研究进展,主要从药物修饰、材料递送、基因编辑等方面进行了总结,希望能为推动线粒体的研究提供一些新的思路。     

油松细胞质遗传的细胞学机理:Ⅱ.雄性和雌性细胞器在受精和原胚时期的传递(英文)

在电镜下观察油松 (PinustabulaeformisCarr.)传粉后的胚珠临近受精时的花粉管和卵细胞的细胞质、受精时雄配子体细胞质的传递、游离核和细胞原胚发育时期质体和线粒体的传递。在成熟卵细胞中含许多线粒体 ,缺少正常结构的质体 ,它们转变为大内含体。此外 ,卵细胞还有丰富的小内含体和其他一些细胞器。花粉管在卵细胞的珠孔端释放其内含物。精核与卵核融合时 ,核周围未见来自精细胞的质体和线粒体。不参与融合的精核停留在接受液泡旁 ,在其周围有大量的雄性细胞质 ,其中混合有精细胞、管细胞和卵细胞的细胞器。在游离核原胚时期 ,核周区的细胞质中可见雄性与雌性亲本的细胞器相混合 ;其中许多线粒体与原来卵细胞中的线粒体有相同的形态 ,也有一些线粒体看来是来自精细胞和管细胞 ;质体是由雄配子体传递 ,形态与精细胞的或花粉管中的质体相似。卵细胞中变异的质体 (即大内含体 )在原胚发育时期变为液泡状 ,而雄性质体参加到新细胞质中。在原胚细胞中 ,线粒体大多数为母本来源 ,质体则表现为精细胞或管细胞的质体形态。该研究确定了油松具父系质体和双亲线粒体遗传的细胞学基础。对裸子植物线粒体和质体遗传的机理从细胞学的角度进行了分析。     

线粒体-内质网结构偶联的研究进展

线粒体一内质网结构偶联,是指线粒体外膜与内质网膜之间形成的紧密物理连接。通过“募集”数十种蛋白质（mitofusion2、IP3R、grp75、PACS-2等）构成细胞器间的偶联“平台”,将线粒体和内质网功能联系起来。其中,富集磷脂合成酶与磷脂代谢联系密切：形成高钙离子微区,利于细胞器间Ca^2＋转运,影响钙信号通路,从而决定细胞命运;调控线粒体形态,尤其是线粒体解离过程;此外,线粒体-内质网结构偶联异常还与细胞凋亡、疾病等有关。     

线粒体分裂、融合与细胞凋亡

线粒体是高度动态变化的细胞器,其在细胞内不断分裂、融合并形成网状结构。线粒体的分裂和融合是由多种蛋白质精确调控完成的。Drp1／Dnm1p,Fis1／Fis1p,Caf4p和Mdv1p参与线粒体分裂的调控;Mfn1／2／Fzo1p控制线粒体外膜的融合,而Mgm1p／OPA1则参与线粒体内膜的融合。在细胞凋亡过程中线粒体片段化,网状结构被破坏,线粒体嵴发生重构,抑制这一过程可以部分抑制细胞色素c的释放和细胞凋亡。线粒体形态对于细胞维持正常生理代谢和机体发育起着重要的作用,一旦出现障碍会导致严重的疾病。     

内质网与线粒体接触复合物ERMES在真菌中的结构组成和功能

真核生物细胞中,双层膜细胞器线粒体会进行持续的分裂与融合,从而改变自身形态来满足细胞在不同生长条件下的能量代谢需求.除此之外,线粒体的动态与功能还依赖于与其他细胞器的互作及一些代谢产物在互作过程中的双向交流.与线粒体互作的细胞器包括脂滴、过氧化物酶体、液泡和内质网等.在真菌细胞中,线粒体与内质网的互作由存在二者之间的内...     

Mieap与线粒体的质量控制

线粒体在细胞能量代谢和细胞凋亡中起着至关重要的作用.质量控制是线粒体在细胞中维持正常状态的关键机制.2011年Miyamoto等发现Mieap参与线粒体质量控制的两个新机制.Mieap诱导的溶酶体样细胞器,进入线粒体内,并在线粒体积累,能通过特异性的清除氧化的线粒体蛋白来修复异常线粒体,使得线粒体维持在正常状态.Mieap诱导的通过细胞膜内吞机制形成的囊泡,识别异常线粒体,并对其特异性的清除.Mieap诱导的这两个过程参与了线粒体质量控制,并决定线粒体的命运.     

An ultracytochemical study of the respiratory potency, integrity, and fate of the sea urchin sperm mitochondria during early embryogenesis

Cytochrome oxidase activity via cytochrome c, as demonstrated by the diaminobenzidine procedure, has been employed in this electron microscope cytochemical study to determine the respiratory potency, integrity and fate of the Arbacia sperm mitochondrion at fertilization and during early embryogenesis. The sperm mitochondrion remained intact and was intensely positive for cytochrome oxidase activity both during and after penetration into the egg. The mitochondrion remained highly reactive throughout zygote formation, up to the eight-cell stage. The sperm mitochondrion formed many projections and buds in the cytoplasm of immature oocytes, monospermic and polyspermic eggs, and in blastomeres. At all stages of early embryogenesis, close juxtaposition and structural contact were observed between the highly reactive sperm mitochondrion and the less reactive egg mitochondria. The results suggest that following fertilization the mitochondrion of the sea urchin spermatozoon retains some degree of metabolic autonomy within the ooplasm. The structural integrity of the paternal mitochondrion is maintained along with a functional respiratory enzyme system (cytochrome c-a3). The hypothesis that the fertilizing sperm mitochondrion may have some relevance to sea urchin development is discussed.     

Electron tomographic and ultrastructural analysis of the Cryptosporidium parvum relict mitochondrion, its associated membranes, and organelles

Sporozoites of the apicomplexan Cryptosporidium parvum possess a small, membranous organelle sandwiched between the nucleus and crystalloid body. Based upon immunolabelling data, this organelle was identified as a relict mitochondrion. Transmission electron microscopy and tomographic reconstruction reveal the complex arrangement of membranes in the vicinity of this organelle, as well as its internal organization. The mitochondrion is enveloped by multiple segments of rough endoplasmic reticulum that extend from the outer nuclear envelope. In tomographic reconstructions of the mitochondrion, there is either a single, highly-folded inner membrane or multiple internal subcompartments (which might merge outside the reconstructed volume). The infoldings of the inner membrane lack the tubular "crista junctions" found in typical metazoan, fungal, and protist mitochondria. The absence of this highly conserved structural feature is congruent with the loss, through reductive evolution, of the normal oxidative phosphorylation machinery in C. parvum. It is proposed that the retention of a relict mitochondrion in C. parvum is a strategy for compartmentalizing away from the cytosol toxic ferrous iron and sulfide, which are needed for iron sulfur cluster biosynthesis, an essential function of mitochondria in all eukaryotes.     

Remodeling of Centrosomes in Intraspecies and Interspecies Nuclear Transfer Porcine Embryos

Remodeling of donor cell centrosomes and the centrosome-associated cytoskeleton is crucially important for nuclear cloning as centrosomes are the main microtubule organizing centers that play a significant role in cell division and embryo development. Centrosome dysfunctions have been implicated in various diseases including cancer and metabolic disorders and may also play a role in developmental abnormalities that are frequently seen in cloned animals. In the present studies we investigated microtubule organization and the reorganization and fate of the integral centrosome protein γ-tubulin and the centrosome-associated protein centrin in intraspecies (pig oocytes; pig fetal fibroblast cells) and interspecies (pig oocytes; mouse fibroblast cells) reconstructed embryos by using antibodies to γ-tubulin or GFP-centrin transfected mouse fibroblasts as donor cells. Microtubules were stained with antibodies to α-tubulin. In-vitro-fertilized oocytes and nuclear transfer (NT) reconstructed oocytes were sequentially analyzed at different developmental stages. Epi-fluorescence results revealed mitotic spindle abnormalities in NT embryos during the first cell cycle (39.4%, 13/33) which were significantly higher than those in IVF embryos (17.0%, 7/41). The abnormalities in IVF embryos are due to polyspermy while the abnormalities in NT embryos are due to donor cell centrosome dysfunctions. In the NT embryos with abnormal microtubule and centrosome organization, γ-tubulin staining revealed multipolar centrosome foci while DAPI staining showed misalignment of chromosomes. In intraspecies and interspecies embryos the GFP-centrin signal was detected until 3 hrs after fusion. GFP-centrin was not detected at 8 hrs after NT which is consistent with previous results using anti-centrin antibody staining in intraspecies NT porcine embryos. These data indicate that 1) abnormalities in microtubule and centrosome organization are associated with nuclear cloning at a higher rate than observed in IVF embryos; 2) centrosome and cytoskeletal abnormalities in IVF embryos are due to polyspermy while centrosome and cytoskeletal abnormalities in NT embryos are due to donor cell centrosome dysfunctions; and 3) GFP-centrin of the donor cell centrosome provides a reliable marker to follow its fate in intraspecies reconstructed embryos.     

Blastomere Explants to Test for Cell Fate Commitment During Embryonic Development

Fate maps, constructed from lineage tracing all of the cells of an embryo, reveal which tissues descend from each cell of the embryo. Although fate maps are very useful for identifying the precursors of an organ and for elucidating the developmental path by which the descendant cells populate that organ in the normal embryo, they do not illustrate the full developmental potential of a precursor cell or identify the mechanisms by which its fate is determined. To test for cell fate commitment, one compares a cell''s normal repertoire of descendants in the intact embryo (the fate map) with those expressed after an experimental manipulation. Is the cell''s fate fixed (committed) regardless of the surrounding cellular environment, or is it influenced by external factors provided by its neighbors? Using the comprehensive fate maps of the Xenopus embryo, we describe how to identify, isolate and culture single cleavage stage precursors, called blastomeres. This approach allows one to assess whether these early cells are committed to the fate they acquire in their normal environment in the intact embryo, require interactions with their neighboring cells, or can be influenced to express alternate fates if exposed to other types of signals.     

Cell fate decisions and axis determination in the early mouse embryo

The mouse embryo generates multiple cell lineages, as well as its future body axes in the early phase of its development. The early cell fate decisions lead to the generation of three lineages in the pre-implantation embryo: the epiblast, the primitive endoderm and the trophectoderm. Shortly after implantation, the anterior-posterior axis is firmly established. Recent studies have provided a better understanding of how the earliest cell fate decisions are regulated in the pre-implantation embryo, and how and when the body axes are established in the pregastrulation embryo. In this review, we address the timing of the first cell fate decisions and of the establishment of embryonic polarity, and we ask how far back one can trace their origins.     

Origin of cellular asymmetries in the pre-implantation mouse embryo: a hypothesis

The first cell fate decision during mouse development concerns whether a blastomere will contribute to the inner cell mass (ICM; which gives rise to the embryo proper) or to trophectoderm (TE; which gives rise to the placenta). The position of a cell within an 8- to 16-cell-stage embryo correlates with its future fate, with outer cells contributing to TE and inner cells to the ICM. It remains unknown, however, whether an earlier pre-pattern exists. Here, we propose a hypothesis that could account for generation of such a pre-pattern and which is based on epigenetic asymmetry (such as in histone or DNA methylation) between maternal and paternal genomes in the zygote.     

Fate maps of the primitive streak in chick and quail embryo: ingression timing of progenitor cells of each rostro-caudal axial level of somites

Developmental fates of cells emigrating from the primitive streak were traced by a fluorescent dye Dil both in chick and in quail embryos from the fully grown streak stage to 12-somite stage, focusing on the development of mesoderm and especially on the timing of ingression of each level of somitic mesoderm. The fate maps of the chick and quail streak were alike, although the chick streak was longer at all stages examined. The anterior part of the primitive streak predominantly produced somites. The thoracic and the lumbar somites were shown to begin to ingress at the 5 somite-stage and 10 somite-stage in a chick embryo, and 6 somite-stage and 9 somite-stage in a quail embryo, respectively. The posterior part of the streak served mainly as the origin of more lateral or extra embryonic mesoderm. As development proceeded, the fate of the posterior part of the streak changed from the lateral plate mesoderm to the tail bud mesoderm and then to extra embryonic, allantois mesoderm. The fate map of the primitive streak in chick and quail embryo presented here will serve as basic data for studies on mesoderm development with embryo manipulation, especially for transplantation experiments between chick and quail embryos.