Weismannism Research Articles

Correction to ‘Primoridal germ cell specification: a context-dependent cellular differentiation event’

You have accessMoreSectionsView PDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmail Cite this article Günesdogan Ufuk, Magnúsdóttir Erna and Surani M. Azim 2014Correction to ‘Primoridal germ cell specification: a context-dependent cellular differentiation event’Phil. Trans. R. Soc. B3692014031420140314http://doi.org/10.1098/rstb.2014.0314SectionYou have accessCorrectionCorrection to ‘Primoridal germ cell specification: a context-dependent cellular differentiation event’ Ufuk Günesdogan Ufuk Günesdogan Google Scholar Find this author on PubMed Search for more papers by this author , Erna Magnúsdóttir Erna Magnúsdóttir Google Scholar Find this author on PubMed Search for more papers by this author and M. Azim Surani M. Azim Surani Google Scholar Find this author on PubMed Search for more papers by this author Ufuk Günesdogan Ufuk Günesdogan Google Scholar Find this author on PubMed Search for more papers by this author , Erna Magnúsdóttir Erna Magnúsdóttir Google Scholar Find this author on PubMed Search for more papers by this author and M. Azim Surani M. Azim Surani Google Scholar Find this author on PubMed Search for more papers by this author Published:19 December 2014https://doi.org/10.1098/rstb.2014.0314This article corrects the followingReview ArticlePrimoridal germ cell specification: a context-dependent cellular differentiation eventhttps://doi.org/10.1098/rstb.2013.0543 Ufuk Günesdogan, Erna Magnúsdóttir and M. Azim Surani volume 369issue 1657Philosophical Transactions of the Royal Society B: Biological Sciences05 December 2014Phil. Trans. R. Soc. B369, 20130543 (5 December 2014; Published online 27 October 2014) (doi:10.1098/rstb.2013.0543).The title of the paper should read as ‘Primordial germ cell specification: a context-dependent cellular differentiation event’. Previous Article VIEW FULL TEXT DOWNLOAD PDF FiguresRelatedReferencesDetailsCited by Bline A, Le Goff A and Allard P (2020) What Is Lost in the Weismann Barrier?, Journal of Developmental Biology, 10.3390/jdb8040035, 8:4, (35) Related articlesPrimoridal germ cell specification: a context-dependent cellular differentiation event05 December 2014Philosophical Transactions of the Royal Society B: Biological Sciences This Issue19 December 2014Volume 369Issue 1658Theme Issue ‘Communicative rhythms in brain and behaviour’compiled and edited by Rachel Smith, Tamara Rathcke, Fred Cummins, Katie Overy and Sophie Scott Article InformationDOI:https://doi.org/10.1098/rstb.2014.0314Published by:Royal SocietyPrint ISSN:0962-8436Online ISSN:1471-2970History: Published online19/12/2014Published in print19/12/2014 License:© 2014 The Author(s) Published by the Royal Society. All rights reserved. Citations and impact

Gamete derivation from embryonic stem cells, induced pluripotent stem cells or somatic cell nuclear transfer-derived embryonic stem cells: state of the art.

Generating gametes from pluripotent stem cells (PSCs) has many scientific justifications and several biomedical rationales. Here, we consider several strategies for deriving gametes from PSCs from mice and primates (human and non-human) and their anticipated strengths, challenges and limitations. Although the 'Weismann barrier', which separates the mortal somatic cell lineages from the potentially immortal germline, has long existed, breakthroughs first in mice and now in humans are artificially creating germ cells from somatic cells. Spermatozoa with full reproductive viability establishing multiple generations of seemingly normal offspring have been reported in mice and, in humans, haploid spermatids with correct parent-of-origin imprints have been obtained. Similar progress with making oocytes has been published using mouse PSCs differentiated in vitro into primordial germ cells, which are then cultured after xenografting reconstructed artificial ovaries. Progress in making human oocytes artificially is proving challenging. The usefulness of these artificial gametes, from assessing environmental exposure toxicity to optimising medical treatments to prevent negative off-target effects on fertility, may prove invaluable, as may basic discoveries on the fundamental mechanisms of gametogenesis.

Amphimixis and the individual in evolving populations: does Weismann’s Doctrine apply to all, most or a few organisms?

The German biologist August Weismann (1834-1914) proposed that amphimixis (sexual reproduction) creates variability for natural selection to act upon, and hence he became one of the founders of the Neo-Darwinian theory of biological evolution. He is perhaps best known for what is called "Weismann's Doctrine" or "Weismann's Barrier" (i.e. the irreversible separation of somatic and germ cell functionalities early during ontogeny in multicellular organisms). This concept provided an unassailable argument against "soft inheritance" sensu Lamarck and informed subsequent theorists that the only "individual" in the context of evolution is the mature, reproductive organism. Herein, we review representative model organisms whose embryology conforms to Weismann's Doctrine (e.g. flies and mammals) and those that do not (e.g. freshwater hydroids and plants) based on this survey and the Five Kingdoms of Life scheme; we point out that most species (notably bacteria, fungi, protists and plants) are "non-Weismannian" in ways that make a canonical definition of the "individual" problematic if not impossible. We also review critical life history functional traits that allow us to create a matrix of all theoretically conceivable life cycles (for eukaryotic algae, embryophytes, fungi and animals), which permits us to establish where this scheme Weismann's Doctrine holds true and where it does not. In addition, we argue that bacteria, the dominant organisms of the biosphere, exist in super-cellular biofilms but rarely as single (planktonic) microbes. Our analysis attempts to show that competition among genomic variants in cell lineages played a critical part in the evolution of multicellularity and life cycle diversity. This feature was largely ignored during the formulation of the synthetic theory of biological evolution and its subsequent elaborations.

From DNA- to NA-centrism and the conditions for gene-centrism revisited

First the ‘Weismann barrier’ and later on Francis Crick’s ‘central dogma’ of molecular biology nourished the gene-centric paradigm of life, i.e., the conception of the gene/genome as a ‘central source’ from which hereditary specificity unidirectionally flows or radiates into cellular biochemistry and development. Today, due to advances in molecular genetics and epigenetics, such as the discovery of complex post-genomic and epigenetic processes in which genes are causally integrated, many theorists argue that a gene-centric conception of the organism has become problematic. Here, we first explore the causal implications of the following two central dogma-related issues: (1) widespread reverse transcription—arguing for an extension from ‘DNA-genome’ to RNA-encompassing ‘NA-genome’ and, thus, from traditional DNA-centrism to a broader ‘NA-centrism’; and (2) the absence of a mechanism of reverse translation—arguing for the ‘structural primacy’ of NA-sequence over protein in cellular biochemistry. Secondly, we explore whether this latter conclusion can be extended to a ‘functional primacy’ of NA-sequence over protein in cellular biochemistry, which would imply a limited kind of ‘gene/NA-centrism’ confined to the subcellular level of NA/protein-based biochemistry. Finally, we explore the conditions—and their (non)fulfilment—for a more generalised form of gene-centrism extendable to higher levels of biological organisation. We conclude that the higher we go in the biological hierarchy, the more dubious gene-centric claims become.

Closing the circle of germline and stem cells: the Primordial Stem Cell hypothesis

BackgroundGermline determination is believed to occur by either preformation or epigenesis. Animals that undergo germ cell specification by preformation have a continuous germline. However, animals with germline determination by epigenesis have a discontinuous germline, with somatic cells intercalated. This vision is contrary to August Weismann’s Germ Plasm Theory and has led to several controversies. Recent data from metazoans as diverse as planarians, annelids and sea urchins reveal the presence of pluripotent stem cell populations that express germ plasm components, despite being considered to be somatic. These data also show that germ plasm is continuous in some of these animals, despite their discontinuous germline.Presentation of the hypothesisHere, based on recent molecular data on germ plasm components, I revise the germline concept. I introduce the concept of primordial stem cells, which are evolutionarily conserved stem cells that carry germ plasm components from the zygote to the germ cells. These cells, delineated by the classic concept of the Weismann barrier, can contribute to different extents to somatic tissues or be present in a rudimentary state. The primordial stem cells are a part of the germline that can drive asexual reproduction.Testing the hypothesisMolecular information on the expression of germ plasm components is needed during early development of non-classic model organisms, with special attention to those capable of undergoing asexual reproduction and regeneration. The cell lineage of germ plasm component-containing cells will also shed light on their position with respect to the Weismann barrier. This information will help in understanding the germline and its associated stem cells across metazoan phylogeny.Implications of the hypothesisThis revision of the germline concept explains the extensive similarities observed among stem cells and germline cells in a wide variety of animals, and predicts the expression of germ plasm components in many others. The life history of these animals can be simply explained by changes in the extent of self-renewal, proliferation and developmental potential of the primordial stem cells. The inclusion of the primordial stem cells as a part of the germline, therefore, solves many controversies and provides a continuous germline, just as originally envisaged by August Weismann.

Tuberculosis in London: the importance of homelessness, problem drug use and prison

The control of tuberculosis (TB) is founded on early case detection and complete treatment of disease. In the UK, TB is concentrated in subgroups of the population in large urban centres. The impact of homelessness, imprisonment and problem drug use on TB control in London is reviewed. A cohort study was undertaken of all patients with TB in Greater London to determine the point prevalence of disease in different groups and to examine risk factors for smear positivity, drug resistance, treatment adherence, loss to follow-up and use of directly observed therapy (DOT). Data were collected on 97% (1941/1995) of eligible patients. The overall prevalence of TB was 27 per 100,000. An extremely high prevalence of TB was seen in homeless people (788/100,000), problem drug users (354/100,000) and prisoners (208/100,000). Multivariate analysis showed that problem drug use was associated with smear positive disease (OR 2.2, p<0.001), being part of a known outbreak of drug resistant TB (OR 3.5, p = 0.001) and loss to follow-up (OR 2.7, p<0.001). Imprisonment was associated with being part of the outbreak (OR 10.3, p<0.001) and poor adherence (OR 3.9, p<0.001). Homelessness was associated with infectious TB (OR 1.6, p = 0.05), multidrug resistance (OR 2.1, p = 0.03), poor adherence (OR 2.5, p<0.001) and loss to follow-up (OR 3.8, p<0.001). In London, homeless people, prisoners and problem drug users collectively comprise 17% of TB cases, 44% of smear positive drug resistant cases, 38% of poorly compliant cases and 44% of cases lost to follow-up. 15% of these patients start treatment on DOT but 46% end up on DOT. High levels of infectious and drug resistant disease, poor adherence and loss to follow-up care indicate that TB is not effectively controlled among homeless people, prisoners and problem drug users in London.

Gene duplication and other evolutionary strategies: from the RNA world to the future.

Beginning with a hypothetical RNA world, it is apparent that many evolutionary transitions led to the complexity of extant species. The duplication of genetic material is rooted in the RNA world. One of two major routes of gene amplification, retroposition, originated from mechanisms that facilitated the transition to DNA as hereditary material. Even in modern genomes the process of retroposition leads to genetic novelties including the duplication of protein and RNA coding genes, as well as regulatory elements and their juxtapositon. We examine whether and to what extent known evolutionary principles can be applied to an RNA-based world. We conclude that the major basic Neo-Darwinian principles that include amplification, variation and selection already governed evolution in the RNA and RNP worlds. In this hypothetical RNA world there were few restrictions on the exchange of genetic material and principles that acted as borders at later stages, such as Weismann's Barrier, the Central Dogma of Molecular Biology, or the Darwinian Threshold were absent or rudimentary. RNA was more than a gene: it had a dual role harboring, genotypic and phenotypic capabilities, often in the same molecule. Nuons, any discrete nucleic acid sequences, were selected on an individual basis as well as in groups. The performance and success of an individual nuon was markedly dependent on the type of other nuons in a given cell. In the RNA world the transition may already have begun towards the linkage of nuons to yield a composite linear RNA genome, an arrangement necessitating the origin of RNA processing. A concatenated genome may have curbed unlimited exchange of genetic material; concomitantly, selfish nuons were more difficult to purge. A linked genome may also have constituted the beginning of the phenotype/genotype separation. This division of tasks was expanded when templated protein biosynthesis led to the RNP world, and more so when DNA took over as genetic material. The aforementioned barriers and thresholds increased and the significance and extent of horizontal gene transfer fluctuated over major evolutionary transitions. At the dawn of the most recent transformation, a fast evolutionary transition that we will be witnessing in our life times, a form of Lamarckism is raising its head.

Cells in search of community: Critiques of Weismannism and selectable units in ontogeny

Cells in search of community: Critiques of Weismannism and selectable units in ontogeny

An Examination of Weismannism.

An Examination of Weismannism.

An Examination of Weismannism. George John Romanes

Previous articleNext article FreeRecent LiteratureAn Examination of Weismannism. George John Romanes PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The American Naturalist Volume 28, Number 327Mar., 1894 Published for The American Society of Naturalists Article DOIhttps://doi.org/10.1086/275900 Views: 50Total views on this site PDF download Crossref reports no articles citing this article.

A Difficulty in Weismannism

A Difficulty in Weismannism

A Difficulty in Weismannism

A Difficulty in Weismannism