VI. Earth Life Emergence: Development of Body, Brain, Selves and Societies
D. The Ascent of Genetic Information: DNA/AND
Smith, Laura, et al. Unraveling the Epigenetic Code of Cancer for Therapy. Trends in Genetics. 23/9, 2007. As other citations herein note, a major revolution is underway in our understanding of the nature and activity of genetic processes. Not yet mainstream or fully worked through, it involves a salient shift from the 20th century emphasis on molecular DNA and RNA to this ancillary domain of how ‘genes’ transcribe and translate into the vast variety of proteins and cells. Cancer treatment is a frontier area because it has lately been realized that such cellular decay (also aging deficits) are due more to errors in transmission, rather than point to point genes. And all this seems to beg an analogy with written language where how words are grammatically used in sentences and paragraphs is just as important, probably more so.
It is now evident that an additional layer of information required for proper gene expression is encoded in the genomic sequence and exceeds the information of the four bases: adenine, thymine, guanine and cytosine. This is achieved in the form of epigenetic modifications, which in their entirety represent the ‘epigenome’ (from the Greek prefix epi-, meaning ‘on’ or ‘over’). Epigenetic modifications are heritable and can be transmitted to daughter cells during cell divisions. Most importantly, they leave the option for reprogramming in the context of development and differentiation. (449)
Snyder, Michael and Mark Gerstein. Defining Genes in the Genomics Era. Science. 300/258, 2003. Now that genomes, the entire genetic coding system for a certain organism, are becoming sequenced and transcribed, a new concept of what a gene is results. Rather than particulate in kind, they are more like “a complete chromosomal segment responsible for making a functional product.” (258)
Stoltzfus, Arlin. Mutation Biased Adaptation in a Protein NK Model. Molecular Biology and Evolution. 23/10, 2006. A University of Maryland biologist argues that genetic change is not an accidental variant that passively awaits selection. Rather, new gene configurations act as an “immanent directional orienting factor” upon evolutionary pathways. See also Stoltzfus’ Mutationism and the Dual Causation of Evolutionary Change in Evolution and Development (8/3, 2006) and Google his name.
Thus, it is of interest to consider the possibility that biases or nonrandomness in the rate of origin of new variants by mutation (and more generally, by mutation and altered development) are a general cause of nonrandomness in evolution, a possibility that cuts across traditional scientific disputes over selection versus drift, the Modern Synthesis versus the Neutral Theory, and morphological versus molecular evolution. (1853)
Stotz, Karola. Experimental Philosophy of Biology. Studies in History and Philosophy of Science. 40/2, 2009. A University of Sydney philosopher contributes to the 21st century project to reinvent and redefine genetic phenomena beyond older particulate “genes” so as to include the equally present layers of interactive, relational networks
In this vision the ‘gene’ is relieved of its unrealistic and mystical status as the sole embodiment of life. Instead, genes become prosaic ways to classify the template capacity of certain parts of the genome, a capacity that must be interpreted through a process of gene expression to yield any determinate result. Because of this limited and very context-dependent capacity, the gene is also stripped of its place as the sole unit of inheritance. (237) Inheritance is not embodied in mystical preformations of the phenotype but in the reproduction of the necessary factors of development that will self-organize to reproduce a similar developmental life cycle. Life is not situated in genes but in the particular organization of biomolecules that enables the system to maintain itself by reconstituting its own components from the template capacity in the genome, constructing the environmental factors necessary for this to occur, and ultimately reproducing copies of itself. (237)
Stotz, Karola. The Ingredients for a Postgenomic Synthesis of Nature and Nurture. Philosophical Psychology. 21/3, 2008. An introduction by the University of Sydney scholar to papers from a March 2007 Indiana University symposium on “Reconciling Nature and Nurture in Behavior and Cognition Research.” The shifting genetic paradigm from discrete “programs” to an “interactive” epigenetic context, which involves both the cellular organism and its external environment, is under review, and evokes a sense of molecular “letters and words” and their parsed usage in descriptive sentences and paragraphs. As a growing number of other fields realize, a dynamic dialogue of essential script and contingent evolutionary and developmental editing goes on. Other notable authors herein include Eva Jablonka, Paul Griffiths, Jason Scott Robert, and Edouard Machery.
In other words, the more complex an organism, the more complex the expression of its limited number of coding sequences….what is of particular importance during development is not the existence of some genes but their differential time- and tissue-dependent expression. In the last two decades development has become equated with differential gene expression, but what is hidden behind this equation is the complex network of molecules other than DNA (such as proteins and metabolites), cellular structures, three-dimensional cellular assemblages, and other higher-level structures that control or are otherwise involved not only in the differential expression of genes but in a wide range of other developmental processes decoupled from the direct influence of DNA sequences. (363)
Strohman, Richard. The Coming Kuhnian Revolution in Biology. Nature Biotechnology. 15/3, 1997. A notable statement of the shift underway from a determinism of particulate genes to an embryonic development due to informed dynamic systems similar to neural networks.
The theory is in trouble because it insists on locating the driving force solely in random mutations. An alternative theory of evolution that emphasizes the importance of nonrandom (epigenetic) changes during development could explain the problems now being encountered by evolutionary theory. (195) The cell is starting to look more like a complex adaptive system rather than a factory floor of robotic gene machines, and that is well and good….Many of us are guessing at some kind of complex adaptive system theory that can embrace discontinuous change at all levels of life’s organization. (197)
Sweatt, David. The Emerging Field of Neuroepigenetics. Neuron. 80/3, 2013. In a special Neuroscience Retrospective, a University of Alabama neurobiologist provides a past and future survey of this expansion of genetic phenomena beyond just point nucleotides. The admission that both genes and environment reciprocally interact and cross-contribute then requires a major rethinking such as “What Roles Do Epigenetic Mechanisms Play in Complex Human Diseases of the Nervous System?” and “Are Acquired Epigenetic Marks Transmitted Across Generations?” with regard to an “epigenome code.” See also in this issue The New Science of Mind and the Future of Knowledge by Nobel laureate Eric Kandel.
Over the past 25 years, the broad field of epigenetics and, over the past decade in particular, the emerging field of neuroepigenetics have begun to have tremendous impact in the areas of learned behavior, neurotoxicology, CNS development, cognition, addiction, and psychopathology. However, epigenetics is such a new field that in most of these areas the impact is more in the category of fascinating implications as opposed to established facts. In this brief commentary, I will attempt to address and delineate some of the open questions and areas of opportunity that discoveries in epigenetics are providing to the discipline of neuroscience. (Abstract)
Trieu, Tuan, et al. Hierarchical Reconstruction of High-Resolution 3D Models of Large Chromosomes. Nature Scientific Reports. 9/4971, 2019. University of Missouri bioinformatic scientists Tuan Trieu (Vietman), Oluwatosin Oluwadare (Nigeria), and Jianlin Cheng (China) come together in mid America where they are developing better ways to visualize whole genome structures, as the paper illustrates. An improved image quality is achieved by a novel algorithm which can fully reveal these complex nucleotide packages
Tsuchiya, Masa, et al. Emergent Self-Organized Criticality in Gene Expression Dynamics. PLoS One. June, 2015. In a contribution that can exemplify the current global frontiers of discovery, systems biologists from Japan and Latvia show by theory and experiment that even genomes can be found to exhibit this complex phenomena as everywhere else. The subtitle is Temporal Development of Global Phase Transition Revealed in a Cancer Cell Line. BY these insights a novel 21st century conception of genetic form and activity is achieved, which is then seen as similar to neural network computations. By a turn toward a physical substrate, a further explanation is offered by way of statistical physics and thermodynamics. To reflect on this technical paper, by the mid 2010s the composite, also dynamically self-organizing, worldwide science seems to be reaching an emergent phase of finding a universal repetition of the same common system from universe to human.
Thus, it is natural to abandon a ‘single molecule’ level of explanation when considering self-organization into discrete ‘phenotypic states’ as stable attractor states in the gene-expression landscape. The emergence of a favored ‘globally convergent’ solution that attracts the system dynamics overcomes the problem of stochastic fluctuations related to a gene-by-gene regulation paradigm. (2)
Van Nimwegen, Erik. Scaling Laws in the Functional Content of Genomes. Trends in Genetics. 19/9, 2003. More thoughts on the perception of common natural principles at work.
In this article I show that, for many high-level functional categories, the number of genes in each category scales as a power-law of the total number of genes in the genome. The occurrence of such scaling laws….suggests that the exponents of the observed scaling laws correspond to universal constants of the evolutionary process. (479)
Van Speybroeck, Linda, et al. Epi-Geneticization: Where Biological and Philosophical Thinking Meet. Fagot-Largeault, Anne, et al, eds. The Influence of Genetics on Contemporary Thinking. Berlin: Springer, 2007. In a volume that explores how changing views of genomes work their way into social discourse, Ghent University philosophers survey the epic revolution from 20th century discrete deoxyribonucleic acid molecules, (of course necessary first had to find and name all the pieces). Much more is now seen to be going on which involves a whole array of interconnective network, hierarchical, modular, and informational processes and patterns. By these lights, genomic systems are suffused by and exemplify the same self-organizational properties found throughout nature. But a further conceptual step is then invited, we add. A clear implication would be that these universal, independent propensities that serve organic development and behaviors ought to be appreciated as truly “genetic” in kind. In such regard, they take on a guise and role as a cosmic parental code, with both an original parental independence while being instantiated everywhere in developmental evolution, universe and human in a 21st century temporal, unfolding gestation.
Via the notion of context, a means is found to transcend a reductionist view on genes as sole organizers of both biological organisms and biological knowledge. Within an epigenetic framework, genes no longer stand for inviolable molecular atoms ‘causing’ the organism, but rather for temporarily relatively stable units which take form within a biological system, i.e. a dynamic self-organizing system in which the partaking factors interpret one another, and through this interpretation construct each others functional meaning. (125-126)
Van Speybroeck, Linda, et al, eds. From Epigenesis to Epigenetics: The Genome in Context. Annals of the New York Academy of Sciences. Volume 981, 2002. Conference proceedings which discuss a 21st century revolution in genetics as it moves beyond discrete genes to ‘epigenetic’ effects ranging from self-organization to topological and environmental constraints. A paradigm shift is evident from a ‘gene-centric’ emphasis to genomic systems which can reflect the influence of complexly organized dynamic networks.