细胞抽提物诱导的体细胞重编程

体细胞重编程是指在特定条件下将已分化的体细胞去分化逆转回原始多能状态或转分化为其他类型细胞。目前诱导体细胞重编程的方法主要有：体细胞核移植、细胞融合、特定转录因子转染、细胞抽提物诱导等。近年来抽提物诱导体细胞重编程越来越受到研究者的关注。利用此法, 通过重编程不仅可以获得需要类型的细胞, 而且方便识别与重编程有关的细胞因子, 探求重编程的机制。文章简略概述诱导体细胞重编程的方法, 并重点阐述细胞抽提物诱导体细胞重编程的研究进展。     

体细胞重编程为多能干细胞的研究进展

体细胞通过重编程转变成其他类型的细胞,在再生医学方面具有重要的应用前景。细胞重编程的方法主要有体细胞核移植、细胞融合、细胞提取物诱导、限定因子诱导等,这些方法可以不同程度地改变细胞命运。最近,限定因子诱导的多能干细胞（induced pluripotent stem cell。iPS）为重编程提供了一种崭新的方法,不仅可以避免伦理争议,还提供了一种更为便利的技术,为再生医学开辟了新的天地;同时,iPS技术为研究基因表达调控、蛋白质互作、机体生长发育等提供了一个非常重要的研究手段。本文主要论述了体细胞重编程的方法及iPS细胞的进展、面临的问题和应用前景。     

Somatic cell reprogramming for regenerative medicine: SCNT vs. iPS cells

Reprogramming of somatic cells to a pluripotent state holds huge potentials for regenerative medicine. However, a debate over which method is better, somatic cell nuclear transfer (SCNT) or induced pluripotent stem (iPS) cells, still persists. Both approaches have the potential to generate patient-specific pluripotent stem cells for replacement therapy. Yet, although SCNT has been successfully applied in various vertebrates, no human pluripotent stem cells have been generated by SCNT due to technical, legal and ethical difficulties. On the other hand, human iPS cell lines have been reported from both healthy and diseased individuals. A recent study reported the generation of triploid human pluripotent stem cells by transferring somatic nuclei into oocytes, a variant form of SCNT. In this essay, we discuss this progress and the potentials of these two reprogramming approaches for regenerative medicine.     

A key to totipotency: Wuschel-like homeobox 2a unlocks embryogenic culture response in maize (Zea mays L.)

The ability of plant somatic cells to dedifferentiate, form somatic embryos and regenerate whole plants in vitro has been harnessed for both clonal propagation and as a key component of plant genetic engineering systems. Embryogenic culture response is significantly limited, however, by plant genotype in most species. This impedes advancements in both plant transformation-based functional genomics research and crop improvement efforts. We utilized natural variation among maize inbred lines to genetically map somatic embryo generation potential in tissue culture and identify candidate genes underlying totipotency. Using a series of maize lines derived from crosses involving the culturable parent A188 and the non-responsive parent B73, we identified a region on chromosome 3 associated with embryogenic culture response and focused on three candidate genes within the region based on genetic position and expression pattern. Two candidate genes showed no effect when ectopically expressed in B73, but the gene Wox2a was found to induce somatic embryogenesis and embryogenic callus proliferation. Transgenic B73 cells with strong constitutive expression of the B73 and A188 coding sequences of Wox2a were found to produce somatic embryos at similar frequencies, demonstrating that sufficient expression of either allele could rescue the embryogenic culture phenotype. Transgenic B73 plants were regenerated from the somatic embryos without chemical selection and no pleiotropic effects were observed in the Wox2a overexpression lines in the regenerated T0 plants or in the two independent events which produced T1 progeny. In addition to linking natural variation in tissue culture response to Wox2a, our data support the utility of Wox2a in enabling transformation of recalcitrant genotypes.     

细胞命运转变——谱系重编程技术研究进展

体细胞核移植和诱导多能干细胞技术表明已分化的体细胞可以转变命运。最近的研究再一次验证了成熟体细胞可以通过外源转录因子的导入,直接重编程为其他类型的体细胞或祖细胞。这种重编程技术称为谱系重编程(Lineage reprogramming)。这项技术不仅在再生医学领域具有广阔的应用前景,而且在动物生物技术中也应用广泛。它不但避免了伦理争议,还提供了便利的重编程方法,同时也为基因表达调控的研究提供了重要的手段。文章从谱系重编程的方式、谱系重编程的特点及应用前景等3个方面进行了综述,旨在对相关领域的研究人员起到借鉴作用。     

Genetic Control of Totipotency of Plant Cells in an in vitro Culture

The main approaches have been considered to studying the genetic control of plant cell totipotency in an in vitro culture. The capacity of cultured plants for callusogenesis, organ formation, and somatic embryogenesis depends on the activity of genes that determine and maintain the meristematic state of cells, level of hormones in the cells, and sensitivity to hormones, as well as on the activity other genes that control different stages of plant morphogenesis.     

核重编程机制的影响因素

哺乳动物体细胞核移植技术在农业、生物技术、医药生产和濒危动物保护等方面具有很大的潜力和应用价值,已成为目前发育生物学研究的重要方法。但是核重编程仍是核移植技术的关键因素,制约了重构胚胎干细胞的研究。只有供核发生完全重编程,重构胚胎才能正常发育。核重编程与供核者的年龄,供核细胞的组织来源、分化状态、细胞周期、传代次数,供核细胞的表观遗传标记以及供卵者的年龄、卵子的成熟度等因素有关。创造各种适于核重编程的条件有利于从更高的起点开展核移植胚胎干细胞的研究,提高重枸胚胎干细胞建系效率。     

体细胞重编程为多潜能干细胞的研究进展

人类的胚胎干细胞（embryonic stem cells,ES cells）可以用来治疗很多疾病,但是如果通过核移植来获得与供体或者患者相匹配的ES细胞,就会受到人卵母细胞来源等条件的制约。这就促使了将体细胞重编程为多潜能细胞这样一种技术策略的发展,其中包括将分化细胞与ES细胞融合,在卵细胞、ES细胞或多潜能癌细胞的抽提物中孵育,强制多潜能因子过表达等具体的方法。通过这些途径引出了一些核功能的重编程以及相应的DNA甲基化修饰、组蛋白翻译后修饰,使体细胞表达特定的多潜能因子,转变为类似胚胎干细胞的多潜能细胞。     

细胞核重编程对克隆的影响

细胞核重编程是哺乳动物正常受精胚胎和克隆胚胎发育过程中的一个重要特性,主要是对表观遗传学特征进行重新编写,包括染色质重塑、组蛋白修饰、DNA甲基化、印记基因表达、X染色体失活等表观遗传修饰的改变。通过细胞核重编程,首先,受精卵和克隆胚胎的供体核停止其特有的基因表达程序,恢复为全能状态的基因表达程序;然后,受精胚胎和克隆胚胎的细胞再从全能状态重新进入分化状态,最终形成各种组织和器官。近年来,不少研究表明,克隆胚胎的细胞核重编程存在不同程度的表观遗传修饰异常,可能对克隆及其农业和医学应用有着重要影响。本文就正常和克隆胚胎细胞核重编程的研究进展以及克隆胚胎的细胞核重编程异常对克隆的影响作一综述,并对目前有关治疗性克隆前景的不同看法进行了讨论。     

细胞重编程中的表观遗传分子机制

成体细胞可以通过核移植、细胞融合或者特定因子导入的方式实现重编程回到多能性状态。在重编程的过程中,表观遗传水平的调控机制起到了非常关键的作用。通过回顾重编程的研究进展来探讨表观遗传学在重编程中的调控机制。     

珍稀濒危植物香果树胚性细胞悬浮系的建立和植株再生

以香果树（Emmenopterys henry,）未成熟种子为试材,探讨不同的接种量、基本培养基、糖浓度及植物生长调节物质等对体细胞胚胎生长的影响,建立稳定的香果树胚性细胞悬浮培养与植株再生体系。结果表明：悬浮培养条件下,最适接种量为2％（鲜重）：较适合的基本培养基为MS;蔗糖浓度为1％时容易使球形胚聚合体愈伤化,浓度为3％和6％适合球形胚聚合体增殖。浓度为9％则容易使球形胚聚合体褐化：添加0．5mg·L^-1 6-BA和0．5mg·L^-1NAA的MS液体培养基,当初始蔗糖浓度为3％。然后逐步提高到6％则有利于香果树各个发育阶段的同步化;子叶胚转到不含任何植物生长调节物质的MS固体培养基中可以长成正常植株。     

Mechanisms of somatic embryogenesis in cell cultures: Physiology,biochemistry, and molecular biology

Summary One of the most characteristic cell functions in plants is totipotency. Somatic embryogenesis can be regarded as a model system for the investigation of mechanisms of totipotency, because a high frequency and synchronous embryogenic system from single somatic cells has been established in carrot suspension cultures. Four phases are recognized in this process, and several molecular markers, viz. polypeptides, mRNAs, antigens against monoclonal antibodies, can be detected during the expression of totipotency, but they disappear during its loss. Four organ-specific genes have been isolated from hypocotyls and roots by differential screening. They were expressed preferentially after the globular-heart stages of embryogenesis, and were strongly suppressed by auxin. A CEM 1 gene was isolated by differential screening of embryogenic cell clusters. This gene was expressed strongly and transiently during the proglobular and globular stages. The sequence of CEM 1 was found to encode a polypeptide showing high homology to the elongation factor isolated from eucaryotic cells. Thus good progress is being made in understanding the basic mechanisms of somatic embryogenesis. Presented in the Session-in-Depth Developmental Biology of Embryogenesis at the 1991 World Congress on Cell and Tissue Culture, Anaheim, California, June 16–20, 1991.     

细胞重编程的分子机制

细胞重编程,尤其是诱导多能性干细胞的出现,给再生医学带来极大的希望。近年来,这方面的研究吸引了众多科学家的参与,也取得了非常丰富的成果。本文主要从转录因子、表观遗传和信号转导等角度,介绍了细胞重编程分子机制研究方面的进展和未来的方向。     

中国细胞重编程和多能干细胞研究进展

近几十年是干细胞领域飞速发展的重要时期。随着中国经济实力的发展壮大,科研实力也在稳步增强,干细胞研究领域达到了国际并跑甚至领跑的水平。本文从体细胞核移植、诱导多能干细胞、单倍体多能干细胞和胚胎早期发育研究4个方面,对中国细胞重编程和干细胞领域的研究进展进行了历史性回顾,总结了中国科学家在相关领域所取得的重要科研成果。随着单细胞测序技术的发展,各种发育过程将实现更为深入的解读,干细胞的临床应用在中国也会大放异彩。     

microRNAs和体细胞重编程

体细胞重编程与microRNAs(miRNAs)均为近年来研究的热点问题。到目前为止,能成功诱导体细胞形成多能性干细胞的体细胞重编程方法有核移植(nuclear transfer,NT)和外源因子诱导形成多能干细胞(induced pluripotent stem cells,iPSc)两种,这两种方法让人们看到了体细胞重编程在细胞治疗方面具有诱人的应用前景。miRNAs是真核生物中存在的一类长度为22nt左右起调控作用的内源性非编码RNA,它在转录后水平调节靶基因的表达,是细胞内基因表达的基本调控机制之一。近年的研究结果表明,miRNAs在干细胞干性维持和分化过程中具有重要的调节作用,从miRNAs角度研究体细胞重编程机理将对体细胞重编程的应用具有重要意义。     

Partial cellular reprogramming: A deep dive into an emerging rejuvenation technology

Aging and age-associated disease are a major medical and societal burden in need of effective treatments. Cellular reprogramming is a biological process capable of modulating cell fate and cellular age. Harnessing the rejuvenating benefits without altering cell identity via partial cellular reprogramming has emerged as a novel translational strategy with therapeutic potential and strong commercial interests. Here, we explore the aging-related benefits of partial cellular reprogramming while examining limitations and future directions for the field.