Browsing by Subject "Embryo"

Now showing 1 - 6 of 6
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    Definitive Hematopoiesis in the Yolk Sac Emerges from Wnt-Responsive Hemogenic Endothelium Independently of Circulation and Arterial Identity
    (Wiley, 2016-02) Frame, Jenna M.; Fegan, Katherine H.; Conway, Simon J.; McGrath, Kathleen E.; Palis, James; Department of Pediatrics, IU School of Medicine
    Adult-repopulating hematopoietic stem cells (HSCs) emerge in low numbers in the midgestation mouse embryo from a subset of arterial endothelium, through an endothelial-to-hematopoietic transition. HSC-producing arterial hemogenic endothelium relies on the establishment of embryonic blood flow and arterial identity, and requires β-catenin signaling. Specified prior to and during the formation of these initial HSCs are thousands of yolk sac-derived erythro-myeloid progenitors (EMPs). EMPs ensure embryonic survival prior to the establishment of a permanent hematopoietic system, and provide subsets of long-lived tissue macrophages. While an endothelial origin for these HSC-independent definitive progenitors is also accepted, the spatial location and temporal output of yolk sac hemogenic endothelium over developmental time remain undefined. We performed a spatiotemporal analysis of EMP emergence, and document the morphological steps of the endothelial-to-hematopoietic transition. Emergence of rounded EMPs from polygonal clusters of Kit(+) cells initiates prior to the establishment of arborized arterial and venous vasculature in the yolk sac. Interestingly, Kit(+) polygonal clusters are detected in both arterial and venous vessels after remodeling. To determine whether there are similar mechanisms regulating the specification of EMPs with other angiogenic signals regulating adult-repopulating HSCs, we investigated the role of embryonic blood flow and Wnt/β-catenin signaling during EMP emergence. In embryos lacking a functional circulation, rounded Kit(+) EMPs still fully emerge from unremodeled yolk sac vasculature. In contrast, canonical Wnt signaling appears to be a common mechanism regulating hematopoietic emergence from hemogenic endothelium. These data illustrate the heterogeneity in hematopoietic output and spatiotemporal regulation of primary embryonic hemogenic endothelium.
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    Diverse Perspectives: Considerations About Embryonic Stem Cell Research
    (2006-09-01T18:18:29Z) Indiana University Center for Bioethics, Stem Cell Study Group
    Since the initial isolation of human embryonic stem cells in 1998 (Thomson et al. 1998), important developments in research have offered the promise of valuable therapeutic breakthroughs while continuing to raise significant social, ethical, legal and policy challenges. Among the interests of the Indiana University Center for Bioethics (IUCB) is a desire to engage issues of this kind, and in so doing, to provide a resource to the IU community, to Indiana, and to the entire country. The topic of stem cell research was, therefore, an appropriate one for discussion at the Center. In January 2002, the IUCB created a Stem Cell Study Group (SCSG). Our primary goal was to provide a forum for informed public discussion of the issues by making use of the considerable local scientific, legal and ethical expertise. In other words, we wanted primarily to educate ourselves about these issues. Our secondary goal was to identify and describe those points on which agreement could be achieved, as well as those issues on which agreement proved difficult if not impossible. This paper summarizes our efforts to meet both of these goals.
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    Embryo Adoption: Implications of Personhood, Marriage, and Parenthood
    (2008-04-14T12:30:19Z) McMillen, Brooke Marie; Brand, Peggy Zeglin; Eberl, Jason T.; Burke, Michael B.
    One’s personal claims regarding personhood will influence his moral belief regarding embryo adoption. In Chapter One, I consider the personhood of the human embryo. If the human embryo is a person, we are morally obligated to permit the practice of embryo adoption as an ethical means to save human persons. However, for those who do not claim that an embryo is a person at conception, embryo adoption is not a necessary practice because we have no moral obligation to protect them. There are still others who claim that personhood is gained at some point during gestation when certain mental capacities develop. I offer my own claim that consciousness and sentience as well as the potential to be self-conscious mark the beginning of personhood. Embryo adoption raises several questions surrounding the institution of marriage. Due to its untraditional method of procreation, embryo adoption calls into question the role of procreation within marriage. In Chapter Two, I explore the nature of the marriage relationship by offering Lisa Cahill’s definition of marriage which involves both a spiritual and physical dimension, and then I describe the concept of marriage from different perspectives including a social, religious, and a personal perspective. From a personal perspective, I explore the relationship between marriage and friendship. Finally, I describe how the concept of marriage is understood today and explore the advantages to being married as opposed to the advantages of being single. Embryo adoption changes the way we customarily think about procreation within a family because in embryo adoption, couples are seeking an embryo from another union to be implanted into the woman. This prompts some philosophers to argue that embryo adoption violates the marriage relationship. In Chapter Three, I further consider the impact of embryo adoption on the family as an extension of the marital relationship as well as the impact of embryo adoption on the traditional roles of motherhood and fatherhood. I examine motherhood by looking at how some philosophers define motherhood and when these philosophers claim a woman becomes a mother. After considering these issues regarding motherhood, I examine the same issues surrounding fatherhood. Peg Brand, PhD., Chair
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    Ergon and the Embryo
    (2008-10-13T19:05:03Z) Brown, Brandon Patrick; Eberl, Jason T.
    Ethical considerations of the human embryo have involved heated dispute and seem always to result in the same interminable debate. A history of this debate, however, shows a shift in the language used to distinguish between degrees of moral status – while the debate once focused on the presence or absence of “human life,” now it is more likely to hear whether the qualifications for “personhood” have been met. In other words, any member of the human species may deserve some level of respect, but only the “persons” deserve full moral respect. This leaves open the possibility for a human being who is not actually a person – a “nonperson human being.” As an answer to the question of exactly what kind of respect to give the human embryo, Aristotelian moral philosophy offers a unique perspective, one which is distinctive from the familiar debate. Aristotle’s concept of ergon, or function, is a key to understanding what is essential in any human being, because it reveals the importance of potentiality to our nature as rational beings. A philosophical view of function, combined with the data of modern embryology, makes the case that our proper function is the vital part of who we are as human beings, and that a disruption of human function constitutes a true harm. This thesis contrasts Aristotelian proper human function with the modern understanding of a “nonperson human being,” especially as articulated within the ethical theory of Peter Singer. This understanding of function, revealing the essence of human potential and linked with human development, offers a sort of “common-sense morality” response to modern views on personhood.
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    PreImplantation factor (PIF) protects cultured embryos against oxidative stress: relevance for recurrent pregnancy loss (RPL) therapy
    (Impact Journals, 2017-05-16) Goodale, Lindsay F.; Hayrabedran, Soren; Todorova, Krassimira; Roussev, Roumen; Ramu, Sivakumar; Stamatkin, Christopher; Coulam, Carolyn B.; Barnea, Eytan R.; Gilbert, Robert O.; Medicine, School of Medicine
    Recurrent pregnancy loss (RPL) affects 2-3% of couples. Despite a detailed work-up, the etiology is frequently undefined, leading to non-targeted therapy. Viable embryos and placentae express PreImplantation Factor (PIF). Maternal circulating PIF regulates systemic immunity and reduces circulating natural killer cells cytotoxicity in RPL patients. PIF promotes singly cultured embryos' development while anti-PIF antibody abrogates it. RPL serum induced embryo toxicity is negated by PIF. We report that PIF rescues delayed embryo development caused by <3 kDa RPL serum fraction likely by reducing reactive oxygen species (ROS). We reveal that protein disulfide isomerase/thioredoxin (PDI/TRX) is a prime PIF target in the embryo, rendering it an important ROS scavenger. The 16F16-PDI/TRX inhibitor drastically reduced blastocyst development while exogenous PIF increased >2 fold the number of embryos reaching the blastocyst stage. Mechanistically, PDI-inhibitor preferentially binds covalently to oxidized PDI over its reduced form where PIF avidly binds. PIF by targeting PDI/TRX at a distinct site limits the inhibitor's pro-oxidative effects. The >3kDa RPL serum increased embryo demise by three-fold, an effect negated by PIF. However, embryo toxicity was not associated with the presence of putative anti-PIF antibodies. Collectively, PIF protects cultured embryos both against ROS, and higher molecular weight toxins. Using PIF for optimizing in vitro fertilization embryos development and reducing RPL is warranted.
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    USP21 deubiquitylates Nanog to regulate protein stability and stem cell pluripotency
    (Nature Publishing group, 2016-11-04) Liu, Xingyu; Yao, Yuying; Ding, Huiguo; Han, Chuanchun; Chen, Yuhan; Zhang, Yuan; Wang, Chanjuan; Zhang, Xin; Zhang, Yiling; Zhai, Yun; Wang, Ping; Wei, Wenyi; Zhang, Jing; Zhang, Lingqiang; Microbiology and Immunology, School of Medicine
    The homeobox transcription factor Nanog has a vital role in maintaining pluripotency and self-renewal of embryonic stem cells (ESCs). Stabilization of Nanog proteins is essential for ESCs. The ubiquitin–proteasome pathway mediated by E3 ubiquitin ligases and deubiquitylases is one of the key ways to regulate protein levels and functions. Although ubiquitylation of Nanog catalyzed by the ligase FBXW8 has been demonstrated, the deubiquitylase that maintains the protein levels of Nanog in ESCs yet to be defined. In this study, we identify the ubiquitin-specific peptidase 21 (USP21) as a deubiquitylase for Nanog, but not for Oct4 or Sox2. USP21 interacts with Nanog protein in ESCs in vivo and in vitro. The C-terminal USP domain of USP21 and the C-domain of Nanog are responsible for this interaction. USP21 deubiquitylates the K48-type linkage of the ubiquitin chain of Nanog, stabilizing Nanog. USP21-mediated Nanog stabilization is enhanced in mouse ESCs and this stabilization is required to maintain the pluripotential state of the ESCs. Depletion of USP21 in mouse ESCs leads to Nanog degradation and ESC differentiation. Overall, our results demonstrate that USP21 maintains the stemness of mouse ESCs through deubiquitylating and stabilizing Nanog.