Future and applications of cloning

Genome Editing: Promoting Responsible Research

For more than 40 years, scientists have been developing tools and technologies for genome modification; however, initial progress was slow and few outside of the molecular biology community took an interest in the field. Everything has dramatically changed with the recent appearance of the so-called precision approaches, and especially with the 'CRISPR (Clustered Regularly Interspaced Short Palindromic Repeat) revolution'. With great powers come great responsibilities. CRISPR-derived technologies have been proven efficient, cheap, rather easy and fast, and provided universal access to genome modification techniques beyond the leading research centers and reference laboratories. The popularization of techniques to manipulate the human genome and that of all other living beings consequently raises many essential questions, on the ethical and legal sides, both for the scientific community and the lay public. In order to mitigate excessive hype and concern among citizens, a call for the mobilization of the various stakeholders is now urgent through a global governance of genome editing.

Concepts and tools for gene editing

Gene editing is a relatively recent concept in the molecular biology field. Traditional genetic modifications in animals relied on a classical toolbox that, aside from some technical improvements and additions, remained unchanged for many years. Classical methods involved direct delivery of DNA sequences into embryos or the use of embryonic stem cells for those few species (mice and rats) where it was possible to establish them. For livestock, the advent of somatic cell nuclear transfer platforms provided alternative, but technically challenging, approaches for the genetic alteration of loci at will. However, the entire landscape changed with the appearance of different classes of genome editors, from initial zinc finger nucleases, to transcription activator-like effector nucleases and, most recently, with the development of clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated proteins (Cas). Gene editing is currently achieved by CRISPR–Cas-mediated methods, and this technological advancement has boosted our capacity to generate almost any genetically altered animal that can be envisaged.

An organism arises from every nucleus

The fact that, cloning using somatic cell nuclear transfer (SCNT) method has been performed, opened new horizons for cloning, and changed the way of our understanding and approach to cell and nucleus. The progress in cloning technology, brought the anticipation of the ability to clone an organism from each somatic cell nucleus. Therefore, the 'Cell Theory' is about to take the additional statement as "An organism arises from every nucleus". The development of gene targeting procedures which can be applied with SCNT, showed us that it may be possible to obtain different versions of the original genetic constitution of a cell. Because of this opportunity which is provided by SCNT, in reproductive cloning, it would be possible to clone enhanced organisms which can adapt to different environmental conditions and survive. Furthermore, regaining the genetic characteristics of ancestors or reverse herediter variations would be possible. On the other hand, in therapeutic cloning, more precise and easily obtainable alternatives for cell replacement therapy could be presented. However, while producing healthier or different organisms from a nucleus, it is hard to foresee the side effects influencing natural processes in long term is rather difficult.

Issues and ethical problems of stem cell therapy--where is Hippocrates?

Stem cells and their therapeutic use present many questions associated with ethical problems in medicine. There is great effort on the part of physicians to help millions of patients while there are ethical problems with the use of new methods and technologies and all of these are affected by economic and political influences. How will the current generation deal with these problems? Medicine, in this begard, is experiencing a stormy evolution of human culture in the relationships between disease, patient and doctor. Philosophy approaches the same juncture of human culture, but seemingly from the other side. Both disciplines are facing a great problem: How to unite the content of current human morality and the desire for health? Both philosophers and physicians perceive this deficit in human culture as it does not provide immediately usable normatives, which the living generation of healthy and ill is waiting for. It may be said that medicine, as many times before, has reached a stage where it cannot rely only on the proved axiologic values from the past, ethical normatives or cultivated moral sense of its subjects. Medicine has no other alternative than to take an active part in resolution of interdisciplinary problems originating from philosophic-biologic or philosophic-medical inquiries of axiologic, ethical, and moral issues. Our paper indicates some ways of the search in forming ethical principles of the stem-cell therapy from the view of biologists and physicians. New ways are recommended in theoretical-methodological interdisciplinary research, especially, in theoretical and experimental biology, and theoretical and clinical medicine, as well as philosophy. In this paper important ethical problems are pointed out in order to find answers to some key problems connected with cell therapy and the use of stem cells.

Nuclear reprogramming: what has been done and potential avenues for improvements

A major challenge for reproductive biologists is the development of novel strategies to improve cloning efficiency. Even in species for which cloning is relatively successful, like cattle, the efficiency is still unacceptably low. In this review article we critically analyse all approaches that have been suggested by different laboratories in the field so far. As will be discussed below, so far none of these gives rise to a dramatic increase in cloning efficiency. Possibly, a multi-step approach including a pre-treatment of donor cells to modify their chromatin, along with improved culture system for cloned embryos would be the most promising.

Nuclear reprogramming and pluripotency of embryonic cells: Application to the isolation of embryonic stem cells in farm animals

Despite their biological and biotechnological interest, pluripotent embryonic stem cell lines (ES cells) have been isolated from cultured embryos only in a very limited number of mammalian species. Here we review the main molecular mechanisms that have been shown in mouse or primates to regulate the maintenance of pluripotency in vitro. We describe the main signaling pathways that participate in the self-renewal of ES cells and provide an outlook on the epigenetic associated mechanisms. We also propose a practical approach to stem cell differentiation that examines the relationships between the genotype of embryos and their culture conditions and consider nuclear reprogramming as a valuable approach in ES cell derivation in farm animals.

Screening for hereditary hemochromatosis: a clinical practice guideline from the American College of Physicians

Hereditary hemochromatosis is a genetic disorder of iron metabolism. Diagnosis of hereditary hemochromatosis is usually based on a combination of various genetic or phenotypic criteria. Decisions regarding screening are difficult because of the variable penetrance of mutations of the HFE gene and the absence of any definitive trials addressing the benefits and risks of therapeutic phlebotomy in asymptomatic patients or those with only laboratory abnormalities. The purpose of this guideline is to increase physician awareness of hereditary hemochromatosis, particularly the variable penetrance of genetic mutations; aid in case finding; and explain the role of genetic testing. This guideline provides recommendations based on a review of evidence in the accompanying background paper by Schmitt and colleagues. The target audience for this guideline is internists and other primary care physicians. The target patient population is all persons who have a probability or susceptibility of developing hereditary hemochromatosis, including the relatives of individuals who already have the disease.