Epigenetics: Transgenerational effects questoned (Introduction)

by David Turell , Sunday, May 22, 2016, 15:49 (2895 days ago) @ David Turell

The simple point is humans are not rodents, where most of the research has been done:-http://nautil.us/blog/epigenetics-has-become-dangerously-fashionable-"Social scientists' excitement surrounds what we can refer to broadly as transgenerational epigenetics. To understand why social scientists have become enamored with it, we must first consider basic genetics. Many metaphors exist for describing and understanding the genome; they all capture the reality that genes provide the information for building and running biological machinery like the human body. -***-“'Development of an organism from a fertilized egg is driven primarily by the actions of regulatory proteins called transcription factors. In sequential waves and combinations, these proteins bind to specific DNA sequences—called cis- regulatory sequences—associated with specific genes, and encourage (activate) or discourage (repress) transcription into mRNA of those genes.” -***-"What could this have to do with social science? Consider a landmark study, ... which practically started the conversation over transgenerational epigenetics. The authors analyzed whether different nurturing styles might influence stress responses in offspring. The findings suggested that different types of nurturing from participant moms impinged on how babies developed by directly tinkering with their gene expression. Let that sink in: Our experiences—such as how our parents treat us—may alter how our genes are expressed, thus impacting our physiological and psychological development. The weightier implication, though, was that these epigenetic “markers” in the genome might also be transmitted to future generations (thus, the “transgenerational” moniker).-***-"Harvard psychologist Steven Pinker reminds us why we shouldn't carelessly fling ourselves on the transgenerational epigenetics bandwagon:-“'Also inflating the epigenetics bubble is a set of findings that genuinely are surprising, namely that some epigenetic markers attached to the DNA strand as a result of environmental signals (generally stressors such as starvation or maternal neglect) can be passed from mother to offspring. These intergenerational effects on gene expression are sometimes misunderstood as Lamarckian, but they're not, because they don't change the DNA sequence, are reversed after one or two generations, are themselves under the control of the genes, and probably represent a Darwinian adaptation by which organisms prepare their offspring for stressful conditions that persist on the order of a generation. (It's also possible that they are merely a form of temporary damage.) Moreover, most of the transgenerational epigenetic effects have been demonstrated in rodents, who reproduce every few months; the extrapolations to long-lived humans are in most instances conjectural or based on unreliably small samples. -***-"That's right, the most compelling evidence for transgenerational epigenetics is in rodents, not humans. We are fans of animal research, but as Pinker noted, the strengths of it (fast reproductive cycles allowing for the study of numerous generations in a short window of time) may also curtail its applicability to humans in this particular case. Additionally, scientists can randomly manipulate a rodent pup's exposure to different parenting/rearing strategies. But doing this with human babies would never fly with a university ethics committee. -***-"Pinker reminded us of another key point. When social scientists say “environment” they mean something very different than when biologists say “environment.” To a geneticist, environment is anything that isn't DNA (in essence, the cellular environment of DNA). To a social scientist, though, the environment captures everything from the way your parents raised you to the international political climate. The cellular environment might be relevant for understanding environmental regulation of gene expression, but this does not necessarily mean that social environments (like neighborhoods) have a similar impact. More time and research is needed to unpack the latter possibility.-"Many of our expert epigenetics research colleagues are deeply embarrassed by the warm, uncritical response their work has attracted from the social sciences,” say Terrie Moffitt, a distinguished clinical psychologist at Duke University, and Amber Beckley, a criminologist also at Duke. “A biologist attendee at a July 2014 Washington, DC workshop on the social and behavioral implications of epigenetics gasped, ‘The biologists there were horrified at the thought . . . we really don't understand the basic biology well enough yet to do this!'”-Comment: A good cautionary article. Social science tends to have loose experimental controls and conclusions.