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. (shrink)

The mammalian egg employs a wide spectrum of epigenome modification machinery to reprogram the sperm nucleus shortly after fertilization. This event is required for transcriptional activation of the paternal/zygotic genome and progression through cleavage divisions. Reprogramming of paternal nuclei requires replacement of sperm protamines with canonical and non‐canonical histones, covalent modification of histone tails, and chemical modification of DNA (notably oxidative demethylation of methylated cytosines). In this essay we highlight the role maternal histone variants play during developmental reprogramming (...) following fertilization. We discuss how reduced maternal histone variant incorporation in somatic nuclear transfer experiments may explain the reduced viability of resulting embryos and how knowledge of repressive and activating maternal factors may be used to improve somatic cell reprogramming. (shrink)

Emerging evidence suggests that microRNA (miRNA)‐mediated post‐transcriptional gene regulation plays an essential role in modulating embryonic stem (ES) cell pluripotency maintenance, differentiation, and reprogramming of somatic cells to an ES cell‐like state. Investigations from ES cell‐enriched miRNAs, such as mouse miR‐290 cluster and human miR‐302 cluster, and ES cell‐depleted miRNAs such as let‐7 family miRNAs, revealed a common theme that miRNAs target diverse cellular processes including cell cycle regulators, signaling pathway effectors, transcription factors, (...) and epigenetic modifiers and shape their protein output. The combinatorial effects downstream of miRNA action allow miRNAs to modulate cell‐fate decisions effectively. Furthermore, the transcription and biogenesis of miRNAs are also tightly regulated. Thus, elucidating the interplay between miRNAs and other modes of gene regulation will shed new light on the biology of pluripotent stem cells and somatic cell reprogramming. (shrink)

Despite the progress achieved over the last decade after the birth of the first cloned mammal, the efficiency of reproductive cloning remains invariably low. However, research aiming at the use of nuclear transfer for the production of patient‐tailored stem cells for cell/tissue therapy is progressing rapidly. Yet, reproductive cloning has many potential implications for animal breeding, transgenic research and the conservation of endangered species. In this article we suggest that the changes in the epi‐/genotype observed in cloned embryos arise (...) from unbalanced nuclear reprogramming between parental chromosomes. It is probable that the oocyte reprogramming machinery, devised for resident chromosomes, cannot target the paternal alleles of somatic cells. We, therefore, suggest that a reasonable approach to balance this asymmetry in nuclear reprogramming might involve the transient expression in donor cells of chromatin remodelling proteins, which are physiologically expressed during spermatogenesis, in order to induce a male‐specific chromatin organisation in the somatic cells before nuclear transfer. BioEssays 30:66–74, 2008. © 2007 Wiley Periodicals, Inc. (shrink)

The stunning possibility of “reprogramming” differentiated somatic cells to express a pluripotent stem cell phenotype (iPS, induced pluripotent stem cell) and the “ground state” character of pluripotency reveal fundamental features of cell fate regulation that lie beyond existing paradigms. The rarity of reprogramming events appears to contradict the robustness with which the unfathomably complex phenotype of stem cells can reliably be generated. This apparent paradox, however, is naturally explained by the rugged “epigenetic landscape” with (...) valleys representing “preprogrammed” attractor states that emerge from the dynamical constraints of the gene regulatory network. This article provides a pedagogical primer to the fundamental principles of gene regulatory networks as integrated dynamic systems and reviews recent insights in gene expression noise and fate determination, thereby offering a formal framework that may help us to understand why cell fate reprogramming events are inherently rare and yet so robust. (shrink)

Louise Brown's birth in 1978 heralded a new era not just in reproductive technology, but in the relationship between science, cells, and society. For the first time, human embryos could be created, selected, studied, manipulated, frozen, altered, or destroyed, outside the human body. But with this possibility came a plethora of ethical questions. Is it acceptable to destroy a human embryo for the purpose of research? Or to create an embryo with the specific purpose of destroying it for research? In (...) an attempt to construct ethical and legal frameworks for the new era of cellular reprogramming, legislators and ethicists have tried to distinguish between different kinds of biological entity. We treat cells differently depending on whether they are human or animal, somatic cells or gametes, and on whether they are embryos or not. But this approach to the ethics of cellular reprogramming is doomed to failure for the simple reason that cellular reprogramming in itself destroys the distinctions that the law requires to function. In this article, we explore the historical trajectory of cellular reprogramming and its relationship with ethics and society. We suggest that the early hype of embryo research has not obviously fulfilled expectations, but since new avenues of research are continuously opening, it is hard to say definitely that these promises have been broken. We explore the forthcoming challenges posed by the creation of DNA from scratch in the laboratory, and the implications of this for understandings of identity, privacy, and reproduction. We conclude that while ethics used to seek answers in biological facts, this is no longer possible, and a new approach is required. (shrink)

The demonstration that pluripotent stem cells could be generated by somatic cell reprogramming led to wonder if these so-called induced pluripotent stem (iPS) cells would extend our investigation capabilities in the cancer research field. The first iPS cells derived from cancer cells have now revealed the benefits and potential pitfalls of this new model. iPS cells appear to be an innovative approach to decipher the steps of cell transformation as well as to screen the activity and (...) toxicity of anticancer drugs. A better understanding of the impact of reprogramming on cancer cell-specific features as well as improvements in culture conditions to integrate the role of the microenvironment in their behavior may strengthen the epistemic interest of iPS cells as model systems in oncology. (shrink)

In lieu of an abstract, here is a brief excerpt of the content:Direct Nuclear Reprogramming: Response to Condic, Lee, and GeorgeGerard Magill, Ph.D. and William B. NeavesWe read with great interest the response of Maureen Condic, Patrick Lee, and Robert George (2009) to our essay, “Ontological and Ethical Implications of Direct Nuclear Reprogramming” in the March 2009 issue of the Kennedy Institute of Ethics Journal (Magill and Neaves 2009). Much of their response addressed issues that are not in (...) dispute: somatic cells are not zygotes, neurons and hepatocytes are different, growth-factor signals from the trophoblast influence development of the inner cell mass, membranes derived from the trophectoderm are critically required for embryonic survival, and stem cells cannot produce a fetus “on their own.”The crucial point of disagreement deals with the fact that iPS cells are not totipotent but zygotes are. Zygotes can generate their own placental structures while iPS cells must be given them through tetraploid complementation. Condic, Lee, and George consider totipotency to be crucial to natural potentiality. We present an alternative view in our essay (Magill and Neaves 2009, pp. 28–29). Placental structures make no lasting contribution to the postnatal organism, and the equivalency of iPS cells with the inner cell mass of the blastocyst is apparent from tetraploid complementation experiments.The respondents acknowledge the following:... somatic cells can be “converted” into zygotes by the process of somatic cell nuclear transfer (SCNT) or direct reprogramming in combination with tetraploid complementation—just as sperm and egg cells can be “converted” into a zygote by the process of natural fertilization—....(Condic, Lee, and George 2009, p. 35)As the respondents recognize, different ways of manipulating cells can lead to embryogenesis: sperm and egg cells in the process of natural fertilization, the enucleated egg and an ordinary body cell in the process of somatic cell nuclear transfer, and reprogrammed skin cells and a tetraploid blastocyst in the case of induced pluripotent stem (iPS) cells. In each case, different cells are manipulated—or “converted” in the respondents’ terminology—in a process that alters their biological fate within a supportive environment facilitating embryogenesis.The developmental potential that resides in the human genome does not unfold in isolation, not even in a zygote. In all cases, whether involving a zygote or an iPS cell, interaction with a supportive environment is required to express the developmental program residing in the genome. [End Page 201]This biological reality supports what we have described as “early cellular development along the continuum of natural potentiality that can result in the formation of a fetus” (Magill and Neaves 2009, p. 30), and it presents a significant challenge to the natural potentiality argument.Gerard MagillVernon F. Gallagher Chair for the Integration of Science, Theology, Philosophy, and Law, and Professor, Center for Healthcare Ethics Duquesne University Pittsburgh, PA.William B. NeavesPresident and CEO Stowers Institute for Medical Research and Professor of Basic Medical Science University of Missouri at Kansas City School of Medicine Kansas City, MOReferencesCondic, Maureen L.; Lee, Patrick; and George, Robert P. 2008. Ontological and Ethical Implications of Direct Nuclear Reprogramming: Response to Magill and Neaves. Kennedy Institute of Ethics Journal 19: 33–40. Google ScholarMagill, Gerard, and Neaves William B. 2009. Ontological and Ethical Implications of Direct Nuclear Reprogramming. Kennedy Institute of Ethics Journal 19: 23–32. Google ScholarCopyright © 2009 The Johns Hopkins University Press... (shrink)

First put forth in June 2005, the altered nuclear transfer-oocyte assisted reprogramming (ANT-OAR) proposal has been promoted as an ethically-acceptable alternative to the embryo-destructive methods now used to obtain embryonic stem cells. According to its proponents, the goal of ANT-OAR is to use the cloning process to create a pluripotent stem cell. This would be achieved through overexpression of the transcription factor Nanog (or a hypothetical substitute) both in the enucleated egg cell and in the somatic (...) cell prior to transfer of its nucleus. Although the ethical acceptability of ANT-OAR has been publicly debated, its scientific feasibility has not. This paper aims to help rectify this situation. It argues that ANT-OAR, as currently conceived, cannot realistically work. It presents evidence from the scientific literature showing that Nanog cannot single-handedly establish pluripotency in cells, but rather works together with a network of other transcription factors to maintain pluripotency. It argues that ANT-OAR is based on a flawed understanding of stem cell biology, and emphasizes that, in this debate about embryonic stem cells, scientists must strive to accurately and realistically assess the feasibility of the embryo research strategies they propose. (shrink)

The paper by Magill and Neaves in this issue of the Journal attempts to rebut the "natural potency" position, based on recent advances in direct reprogramming of somatic cells to yield "induced pluripotent stem" (iPS) cells. As stated by the authors, the natural potency position holds that because "a human embryo directs its own integral organismic function from its beginning . . . there is a whole, albeit immature, and distinct human organism that is intrinsically valuable with the (...) status of inviolability and deserving full moral respect" (p. 26). The authors boldly assert that "The recent production of iPS . . . highlights a prima facie absurdity for the natural potentiality argument" (p. 29). Yet the argument against natural potency is both logically flawed and based on a characterization of the scientific evidence that is factually inaccurate. (shrink)

It has been suggested that future application of stem-cell derived gametes might lead to the possibility for same-sex couples to have genetically related children. Still, for this to become possible, the technique of gamete derivation and techniques of reprogramming somatic cells to a pluripotent state would have to be perfected. Moreover, egg cells would have to be derived from male cells and sperm cells from female cells, which is believed to be particularly difficult, if not impossible. We (...) suggest a more plausible scenario to provide same-sex couples with the possibility to parent a child who is genetically related to both parents. Although technical feasibility is an advantage, disadvantages are that cooperation of a donor of the opposite sex is still required and that the partners are genetically linked to the resulting child in a different degree. However, since in our scenario the donor's genetic contribution would not outweigh any of the parents' genetic contribution, this alternative route may ease the fear for a possible parental claim by the donor. Like many other applications in the field of infertility treatment, the goal to create SCD-gametes for reproductive purposes is largely based on the high value attributed to genetic parenthood. Although we believe that genetic relatedness is neither a necessary nor a sufficient condition for ‘good’ parenthood, we do believe that many people may consider our scenario a welcome alternative. (shrink)

Human induced pluripotent stem cells can be obtained from somatic cells, and their derivation does not require destruction of embryos, thus avoiding ethical problems arising from the destruction of human embryos. This type of stem cell may provide an important tool for stem cell therapy, but it also results in some ethical concerns. It is likely that abnormal reprogramming occurs in the induction of human induced pluripotent stem cells, and that the stem cells generate tumors in (...) the process of stem cell therapy. Human induced pluripotent stem cells should not be used to clone human beings, to produce human germ cells, nor to make human embryos. Informed consent should be obtained from patients in stem cell therapy. (shrink)

Pluripotent stem cells have gained special attraction because of their almost unlimited proliferation and differentiation capacity in vitro. These properties substantiate the potential of pluripotent stem cells in basic research and regenerative medicine. Here three types of in vitro‐cultured pluripotent stem cells (embryonic carcinoma, embryonic stem and induced pluripotent stem cells) are compared in their historical context with respect to their different origin and properties. It became evident that tumourigenicity is an inherent property of pluripotent cells based on p53 down‐regulation, (...) expression of tumour‐related genes and high telomerase activity that allow unlimited proliferation. In addition, culture‐adapted genetic and epigenetic changes may induce tumourigenicity of pluripotent cells. The use of stem cells in regenerative medicine, however, requires non‐malignant cell types and strategies that circumvent stages of malignancy. Reprogramming strategies of adult somatic cells that avoid the tumourigenic state of pluripotency may offer alternatives for future biomedical application. (shrink)

Recent breakthroughs in stem cell differentiation and reprogramming suggest that functional human gametes could soon be created in vitro. While the ethical debate on the uses of in vitro generated gametes (IVG) was originally constrained by the fact that they could be derived only from embryonic stem cell lines, the advent of somatic cell reprogramming, with the possibility to easily derive human induced pluripotent stem cells from any individual, affords now a major leap in (...) the feasibility of IVG derivation and in the scope of their potential applications. In this paper we develop an ethical framework, rooted in recent scientific evidence, to support a robust experimental pipeline that could enable the first-in-human use of IVG. We then apply this framework to the following objectives: (1) a clarification of the genetic parenting options afforded by IVG, along with their ethical underpinnings; (2) a defence of the use of IVG to remedy infertility, broadening their scope to same-sex couples; (3) an assessment of the most far-reaching implications of IVG for multiplex parenting. These include, first, the liberation of parenting roles from the constraints of biological generations in vivo, allowing multiple individuals to engage in genetic parenting together, thus blurring the distinction between biological and social generations. Second, we discuss the conflation of IVG with sequencing technology and its implications for the possibility that prospective parents may choose among a hitherto unprecedented number of potential children. In view of these perspectives, we argue that, contrary to the exhausted paradigm according to which society lags behind science, IVG may represent instead a salient and most visible instance where biotechnological ingenuity could be used in pursuit of social experimentation. (shrink)

BACKGROUND -/- Understanding, modelling and influencing the transition between different states of cells, be it reprogramming of somatic cells to pluripotency or trans-differentiation between cells, is a hot topic in current biomedical and cell-biological research. Nevertheless, the large body of published knowledge in this area is underused, as most results are only represented in natural language, impeding their finding, comparison, aggregation, and usage. Scientific understanding of the complex molecular mechanisms underlying cell transitions could be improved by (...) making essential pieces of knowledge available in a formal (and thus computable) manner. -/- RESULTS -/- We describe the outline of two ontologies for cell phenotypes and for cellular mechanisms which together enable the representation of data curated from the literature or obtained by bioinformatics analyses and thus for building a knowledge base on mechanisms involved in cellular reprogramming. In particular, we discuss how comprehensive ontologies of cell phenotypes and of changes in mechanisms can be designed using the entity-quality (EQ) model. -/- CONCLUSIONS -/- We show that the principles for building cellular ontologies published in this work allow deeper insights into the relations between the continuants (cell phenotypes) and the occurrents (cell mechanism changes) involved in cellular reprogramming, although implementation remains for future work. Further, our design principles lead to ontologies that allow the meaningful application of similarity searches in the spaces of cell phenotypes and of mechanisms, and, especially, of changes of mechanisms during cellular transitions. (shrink)

In 2006, Shinya Yamanaka and colleagues discovered how to reprogram terminally differentiated somatic cells to a pluripotent stem cell state. The resulting induced pluripotent stem cells (iPSCs) made a paradigm shift in the field, further nailing down the disproval of the long‐held dogma that differentiation is unidirectional. The prospect of using iPSCs for patient‐specific cell‐based therapies has been enticing. This promise, however, has been questioned in the last two years as several studies demonstrated intrinsic epigenetic and genomic (...) anomalies in these cells. Here, we not only review the recent critical studies addressing the genome integrity during the reprogramming process, but speculate about the underlying mechanisms that could create de novo genome damage in iPSCs. Finally, we discuss how much an elevated mutation load really matters considering the safety of future therapies with cells heavily cultured in vitro. (shrink)

Two groups of scientists have just announced what is being described as a leap forward in human stem cell research.1–3 Both have found ways of producing what are being called “induced pluripotent cells” , stem cells that they hope will demonstrate the same key properties of regeneration and unrestricted differentiation that human embryonic stem cells possess, but which are derived from skin cells not from embryos. In simple terms, these scientists have succeeded in reprogramming skin cells to behave (...) like hESCs.Stem cell research has been hailed as one of the most important and exciting areas of science, because it is believed that these types of cells will not only play an important part in regenerative medicine, but also yield valuable scientific information. These latest developments in cell reprogramming represent a milestone for stem cell science. No longer does the paradigm of irreversible cell specialisation hold true; instead, almost any type of cell might have the potential to become any other.The advent of techniques for producing these iPCs has also been hailed as an ethical breakthrough. Up until now, the production of hESCs has required a process which involves the destruction of embryos. Many of these embryos are available as by-products of IVF; but in addition, the process of somatic cell nuclear transfer to produce cloned embryonic stem cells requires a supply of human oocytes, which must currently be harvested from female donors at no insignificant cost. In a nutshell, iPCs seem to enable us to produce “embryo-free” human pluripotent stem cells, and in a “gender-neutral” way—that is, without the need for human oocytes.The response from the scientific community, ethical commentators and the public has, however, reflected an inherent confusion over the ethical significance of this research. The anti-embryo …. (shrink)

The possibility of human reproductive cloning has led some bioethicists to suggest that potentiality-based arguments for fetal moral status become untenable, as such arguments would be committed to making the implausible claim that any adult somatic cell is itself a potential person. In this article I defend potentiality-based arguments for fetal moral status against such a reductio. Starling from the widely-held claim that the maintenance of numerical identity throughout successive changes places constraints on what a given entity can (...) plausibly be said to have the potential to become, I argue that the cell reprogramming that takes place in reproductive cloning is such that it produces a new individual, and so adult somatic cells cannot be potential persons. (shrink)

In lieu of an abstract, here is a brief excerpt of the content:Response to Byrnes and FurtonMark T. Brown, Ph.D.In “Moral Complicity in Induced Pluripotent Stem Cell Research” (MCIPS) (Brown 2009), I sketched the moral complicity implications of alternative national stem cell policies with respect to direct reprogramming techniques that appear to result in pluripotent stem cells derived from skin cells, hair cells, and possibly other somatic cells. This aspect of the stem cell debate was (...) considered from the perspective of those who are pro embryo life and who attribute to human embryos a complete set of basic human rights, including a stringent right to life; and from the perspective of advocates of embryonic stem cell research who do not recognize full moral equivalence between human embryos and human children and who do not ascribe to human embryos an inviolable right to life. The moral complicity concerns of embryonic stem cell research advocates focus upon the scope of medical beneficence with respect to patients whose quality of life and personal autonomy are negatively impacted by the interval between the time when they might have gotten effective medical treatment through unimpeded stem cell science and the time at which stem cell science constrained by pro embryo life moral complicity concerns arrives at a similar destination. The moral complicity concerns of embryo life proponents focus upon noncooperation in past and future destruction of human embryos in order to derive in vitro embryonic stem cell lines.Among the policy alternatives considered were proposals that would be responsive to the possibility that induced pluripotent stem cells (iPSC) at some point may provide a source of stem cell lines that would substitute for human embryonic stem [End Page 206] cell (hESC) lines in cell replacement therapy. If functional equivalence between iPSC lines and hESC lines for cell replacement purposes were confirmed, a national stem cell research policy might be crafted that could accommodate the central moral complicity concerns both of persons who are embryo life advocates and of advocates of embryonic stem cell research. Policy alternatives considered in MCIPS included those based upon the assumption that currently existing embryonic stem cell lines are sufficient to conduct iPSC/hESC functional equivalence studies and policy options based upon the assumption that currently existing hESC lines fall short of what would be required for methodologically sound validation studies. The moral complicity implications for those who are embryo life advocates of both sets of policies were outlined, as were the moral complicity implications of alternative policies for embryonic stem cell research advocates. Since moral complicity concerns are one factor that those who formulate national stem cell policy should consider, MCIPS was an attempt to provide some guidance to policymakers with respect to how alternative policies accommodate or fail to accommodate the moral complicity concerns of various constituencies.In a 2008 article, Malcolm Byrnes (2008, p. 286) appears to consider both empirical assumptions regarding the sufficiency of existing stem cell lines for meaningful functional equivalence studies, and for that reason I drew upon his paper to frame the moral complicity implications for advocates of embryo life of national stem cell policy based upon either assumption. In his paper, Byrnes refers both to stem cell scientists who “suggest” that the hESC lines approved by President Bush in 2001 are sufficient and to stem cell scientists who believe that more hESC lines are needed. Based on my reading of his paper, I erroneously included Byrnes in the group who were willing to consider new hESC derivations in order to complete functional equivalence studies. However, my description of the moral complicity implications for advocates of embryo life of policies that enable new hESC derivations was an exercise in contingency planning, and certainly not intended as “a condemnation” of Byrnes (2009, p. 203). Similarly, what Byrnes (2009, p. 204) sees as “ironic” is simply a description later in my paper of policy options based upon an alternative factual assumption.Byrnes’s position seems to be that existing hESC lines are sufficient to conduct iPSC/hESC functional equivalence studies and that no additional hESC lines should be derived. Although it appears that I did mischaracterize Byrnes’s view of the permissibility of deriving additional hESC lines for equivalence studies, I think my interpretation was... (shrink)

An understanding of the factors behind the evolution of multicellularity is one of today’s frontiers in evolutionary biology. This is because multicellular organisms are made of one subset of cells with the capacity to transmit genes to the next generation and another subset responsible for maintaining the functionality of the organism, but incapable of transmitting genes to the next generation. The question arises: why do somatic cells sacrifice their lives for the sake of germline cells? How is germ/soma separation (...) maintained? One conventional answer refers to inclusive fitness theory, according to which somatic cells sacrifice themselves altruistically, because in so doing they enhance the transmission of their genes by virtue of their genetic relatedness to germline cells. In the present article we will argue that this explanation ignores the key role of policing mechanisms in maintaining the germ/soma divide. Based on the pervasiveness of the latter, we argue that the role of altruistic mechanisms in the evolution of multicellularity is limited and that our understanding of this evolution must be enriched through the consideration of coercion mechanisms. (shrink)

The prelude to successful human somatic gene therapy, i.e. the efficient transfer and expression of a variety of human genes into target cells, has already been accomplished in several systems. Safe methods have been devised to do this using non‐viral and viral vectors. Potentially therapeutic genes have been transferred into many accessible cell types, including hematopoietic cells, hepatocytes and cancer cells, in several different approaches to ex vivo gene therapy. Successful in vivo gene therapy requires improvements in tissuetargeting (...) and new vector design, which are already being sought. Gene‐transfer protocols have been approved for human use in inherited diseases, cancer and acquired disorders. Althouth the results of these trials to date have been somewhat disappointing, human somatic cell gene therapy promises to be an effective addition to the arsenal of approaches to the therapy of many human diseases in the 21st century if not sooner. (shrink)

The case of Andrew Gobea, the first child to receive experimental gene therapy for SCID, and a reflection on the associated ethical implications of gene therapy research.

Recent arguments on the ethics of stem cell research have taken a novel approach to the question of the moral status of the embryo. One influential argument focuses on a property that the embryo is said to possess—namely, the property of being an entity with a rational nature or, less controversially, an entity that has the potential to acquire a rational nature—and claims that this property is also possessed by a somatic cell. Since nobody seriously thinks that (...) we have a duty to preserve the countless such cells we wash off our body every day in the shower, the argument is intended as a reductio ad absurdum of the claim that the embryo should be afforded the same moral status as a fully developed human being. This article argues that this argument is not successful and that it consequently plays into the hands of those who oppose embryonic stem cell research. It is therefore better to abandon this argument and focus instead on the different argument that potentiality, as such, is not a sufficient ground for the creation of moral obligations towards the embryo. (shrink)

Somatic cell nuclear transfer (SCNT) remains a controversial technique, one that has elicited a variety of regulatory responses throughout the world. On March 29, 2005, Canada's Assisted Human Reproduction Act came into force. This law prohibits a number of research activities, including SCNT. Given the pluralistic nature of Canadian society, the creation of this law stands as an interesting case study of the policy-making process and how and why a liberal democracy ends up making the relatively rare decision (...) to use a statutory prohibition, backed by severe penalties, to stop a particular scientific activity. In this article, we provide a comprehensive and systematic legal analysis of the legislative process and parliamentary debates associated with the passage of this law. (shrink)

During early embryonic development in several metazoans, accurate DNA replication is ensured by high number of replication origins. This guarantees rapid genome duplication coordinated with fast cell divisions. In Xenopus laevis embryos this program switches to one with a lower number of origins at a developmental stage known as mid‐blastula transition (MBT) when cell cycle length increases and gene transcription starts. Consistent with this regulation, somatic nuclei replicate poorly when transferred to eggs, suggesting the existence of an (...) epigenetic memory suppressing replication assembly origins at all available sites. Recently, it was shown that histone H1 imposes a non‐permissive chromatin configuration preventing replication origin assembly on somatic nuclei. This somatic state can be erased by SSRP1, a subunit of the FACT complex. Here, we further develop the hypothesis that this novel form of epigenetic memory might impact on different areas of vertebrate biology going from nuclear reprogramming to cancer development. (shrink)

The extent to which normal (nonmalignant) cells of the body can evolve through mutation and selection during the lifetime of the organism has been a major unresolved issue in evolutionary and developmental studies. On the one hand, stable multicellular individuality seems to depend on genetic homogeneity and suppression of evolutionary conflicts at the cellular level. On the other hand, the example of clonal selection of lymphocytes indicates that certain forms of somatic mutation and selection are concordant with the organism-level (...) fitness. Recent DNA sequencing and tissue physiology studies suggest that in addition to adaptive immune cells also neurons, epithelial cells, epidermal cells, hematopoietic stem cells and functional cells in solid bodily organs are subject to evolutionary forces during the lifetime of an organism. Here we refer to these recent studies and suggest that the expanding list of somatically evolving cells modifies idealized views of biological individuals as radically different from collectives. (shrink)

We examine whether the current regulatory regime instituted in South Korea and the United States would have prevented Hwang’s potential transgressions in oocyte procurement for somatic cell nuclear transfer, we compare the general aspects and oversight framework of the Bioethics and Biosafety Act in South Korea and the US National Academies’ Guidelines for Human Embryonic Stem Cell Research, and apply the relevant provisions and recommendations to each transgression. We conclude that the Act would institute centralized oversight under (...) governmental auspices while the Guidelines recommend politically-independent, decentralized oversight bodies including a special review body for human embryonic stem cell research at an institutional level and that the Guidelines would have provided more vigorous protection for the women who had undergone oocyte procurement for Hwang’s research than the Act. We also suggest additional regulations to protect those who provide oocytes for research in South Korea. (shrink)

Mos, a protein kinase, is specifically expressed and functions during meiotic maturation (or G2/M progression) of vertebrate oocytes. When expressed ectopically, however, it can also readily induce oncogenic transformation (or uncontrolled G1/S transitions) in somatic cells. In both of these cell types, Mos activates mitogen‐activated protein kinase (MAPK), which seems largely to mediate its different functions in both oocyte maturation and cellular transformation. In oocyte maturation, the Mos‐MAPK pathway probably serves to activate and stabilize M‐phase promoting factor (MPF) (...) (possibly by inhibiting some negative regulator(s) of this factor), while in cellular transformation, it seems to stabilize and activate the nuclear oncoprotein c‐Fos as well as to induce transcription of its gene. Thus, the different functions of Mos in oocytes and somatic cells may arise chiefly from its different MAPK‐mediated targets in the respective cell types. This review discusses the cellular basis that may enable Mos to act differently in oocytes and somatic cells. (shrink)

The majority of higher plants (including almost all important crops) demonstrate strict uniparental maternal inheritance of plasmagenes in the process of conventional sexual crossing; it is therefore impossible to generate heterozygosity for these genes with standard crossing procedures. However, recent experiments have shown that hybrid plants can be produced by somatic cell fusion and that these contain the cytoplasmic genes of both parents. The phenotypic and genetic properties of these hybrid plants are described here.

Cellular interactions in the mammalian ovarian follicle between its germ‐line and somatic cell components are crucial for its development and function. These interactions are mediated by both membrane gap junctions and paracrine factors. Somatic cell‐to‐oocyte communication is essential for oocyte growth and the regulation of meiotic maturation. In particular, granulosa cells provide nutrients and molecular signals that regulate oocyte development. Oocytes, on the other hand, promote the organization of the follicle, the proliferation of granulosa cells, and (...) the differentiation and function of cumulus cells, a subset of granulosa cells. Determining the nature of the oocyte‐to‐granulosa cell signals remains a key challenge for future work. (shrink)

Under certain conditions, the cell cycle can be arrested for a long period of time. Vertebrate oocytes are arrested at G2 phase, while somatic cells arrest at G0 phase. In both cells, nuclei have lost the ability to initiate DNA synthesis. In a pair of recently published papers,1,2 Méchali and colleagues and Coué and colleagues have clarified how frog oocytes prevent untimely DNA synthesis during the long G2 arrest. Intriguingly, they found only Cdc6 is responsible for the inability (...) of immature oocytes to replicate DNA. Cdc6 is a key component for replication licensing, and for G0 cells to re‐enter the proliferative stage. Strikingly similar strategies for preventing the untimely replication in both cells suggest that the suppression of replication licensing is a universal mechanism for securing the prolonged arrest of the cell cycle. BioEssays 25:313–316, 2003. © 2003 Wiley Periodicals, Inc. (shrink)

On the basis of the evidence that tumor development is suppressed by the embryonic microenvironment, some experiments using the factors taken from Zebrafish embryo at precise stages of cell differentiation were made. These experiments demonstrated a significant growth inhibition on different tumor cell lines in vitro. The observed mechanism of tumor growth inhibition is connected with the key-role cell cycle regulation molecules, such as p53 and pRb, which are modified by transcriptional or post-translational processes. Research on apoptosis (...) and differentiation revealed that treatment with these factors induces caspase-3 with a p73 apoptotic-dependent pathway activation and a concurrent significant normalization of e-cadherin and beta-catenin ratio. Other experiments found a synergistic effect on the colon cancer proliferation curve after the concurrent treatment with these factors and 5-fluorouracil. Finally, a product prepared for human therapy demonstrated 19.8% regression and 16% stable disease in an... (shrink)

An important feature of male fertility is the physiological priming of spermatozoa by a multifaceted process collectively referred to as capacitation. The end point of this evasive process is the hyperactivated spermatozoa capable of binding to terminal sugar residues on the egg's extracellular coat, the zona pellucida (ZP), and undergoing acrosomal exocytosis (i.e., induction of the acrosome reaction). The hydrolytic action of acrosomal enzymes released at the site of zona binding, along with the enhanced thrust generated by the hyperactivated beat (...) pattern of the bound spermatozoa, are important factors that regulate the penetration of ZP and fertilization of the egg. Despite many advances in identifying sperm components that promote capacitation, the mechanism underlying the calcium‐triggered process remains elusive. The purpose of this review article is to focus on new advances that have enhanced our understanding of in vivo/in vitro capacitation, a prerequisite event resulting from a dramatic modification and reorganization of the sperm membrane molecules. Special emphasis has been laid on accumulating evidence suggesting potential similarities between the sperm capacitation and early phases of calcium‐triggered membrane fusion (i.e., tethering and docking) during secretory and endocytotic pathways among eukaryotes. BioEssays 26:281–290, 2004. © 2004 Wiley Periodicals, Inc. (shrink)

The recent successful conversion of adult cells into induced pluripotent stem (iPS) cells through direct reprogramming opens a new chapter in the study of disease and the development of regenerative medicine. It also provides a historic opportunity to turn away from the ethically problematic use of embryonic stem cells isolated through the destruction of human embryos. Moreover, because iPS cells are patient specific, they render therapeutic cloning unnecessary. To maximize therapeutic benefit, adult stem cell research will need to (...) be pursued in parallel with studies using iPS cells. Among the four alternative methods presented by the President’s Council on Bioethics, direct reprogram- ming is the most ethically acceptable. Nonetheless, iPS cells are tainted by their association with the human embryonic stem cell lines, derived in the past, which will be required for their validation. This concern is one that can be resolved. Human iPS cells will serve to stem the tide of human embryonic stem cell research, changing it and diverting stem cell research in a more ethical direction. (shrink)