Transgenerational pathological traits induced by prenatal immune activation

The third paper of Transgenerational epigenetic inheritance week is a 2016 Swiss rodent study of immune system epigenetic effects:

“Our study demonstrates for, we believe, the first time that prenatal immune activation can negatively affect brain and behavioral functions in multiple generations. These findings thus highlight a novel pathological aspect of this early-life adversity in shaping disease risk across generations.”

The epigenetic effects noted in the initial round of experiments included:

  • F1 and F2 generation impaired sociability;
  • F1 and F2 abnormal fear expression;
  • F1 but not F2 sensorimotor gating deficiencies; and
  • F2 but not F1 behavioral despair associated with depressive-like behavior.

These transgenerational effects emerged in both male and female offspring. The prenatal immune activation timing corresponded to the middle of the first trimester of human pregnancy.

The effects were found to be mediated by the paternal but not maternal lineage. The researchers didn’t develop a maternal lineage F3 generation.

The next round of experiments done with the paternal lineage noted these epigenetic effects:

  • The F3 generation had impaired sociability, abnormal fear expression and behavioral despair; and
  • The F3 generation had normal sensorimotor gating.

Since the first round of tests didn’t show sex-dependent effects, the F3 generation was male-only to minimize the number of animals.

Samples of only the amygdalar complex were taken to develop findings of transcriptomic effects of prenatal immune activation.

Items in the Discussion section included:

  1. The F2 and F3 generations’ phenotype of impaired sociability, abnormal fear expression and behavioral despair demonstrated that prenatal immune activation likely altered epigenetic marks in the germ line of the F1 generation, which resisted erasure and epigenetic reestablishment during germ cell development.
  2. Abnormal F1 generation sensorimotor gating followed by normal F2 and F3 sensorimotor gating demonstrated that prenatal immune activation may also modify somatic but not germ cells.
  3. Non-significant F1 generation behavioral despair followed by F2 and F3 behavioral despair demonstrated that prenatal immune activation may modify F1 germ cells sufficiently to develop a transgenerational phenotype, but unlike item 1 above, somatic cells were insufficiently modified, and the phenotype skipped the first generation.
  4. Studies were cited that prenatal immune activation later in the gestational process may produce different effects.

The initial round of experiments wasn’t definitive for the maternal lineage. As argued in Transgenerational effects of early environmental insults on aging and disease, a F3 generation from the maternal lineage was needed to confirm several of the study’s findings.

For example, effects that didn’t reach statistical significance in the F1 and F2 maternal lineage may have been different in a F3 generation. The researchers indirectly acknowledged this lack by noting that these and other effects of immune challenges in a maternal lineage weren’t excluded by the study.

https://www.nature.com/mp/journal/v22/n1/pdf/mp201641a.pdf “Transgenerational transmission and modification of pathological traits induced by prenatal immune activation” (not freely available)

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Experience-induced transgenerational programming of neuronal structure and functions

The second paper of Transgenerational epigenetic inheritance week is a 2017 German/Israeli review focused on:

“The inter- and transgenerational effects of stress experience prior to and during gestation..the concept of stress-induced (re-)programming in more detail by highlighting epigenetic mechanisms and particularly those affecting the development of monoaminergic transmitter systems, which constitute the brain’s reward system..we offer some perspectives on the development of protective and therapeutic interventions in cognitive and emotional disturbances resulting from preconception and prenatal stress.”

The reviewers noted that human studies have difficulties predicting adult responses to stress that are based on gene expression and early life experience. Clinical studies that experimentally manipulate the type, level and timing of the stressful exposure aren’t possible. Clinical studies are also predicated on the symptoms being recognized as disorders and/or diseases.

The researchers noted difficulties in human interventions and treatments. Before and during pregnancy, and perinatal periods are where stress effects are largest, but current human research hasn’t gathered sufficient findings to develop practical guidelines for early intervention programs.


I’m not persuaded by arguments that cite the difficulties of performing human research on transgenerational epigenetic inheritance. There are overwhelming numbers of people who have obvious stress symptoms: these didn’t develop in a vacuum.

Researchers:

  • Design human studies to test what’s known from transgenerational epigenetic inheritance animal studies that will include documenting the subjects’ detailed histories with sufficient biometric samples and data obtained from their lineage.
  • Induce the subjects to at least temporarily avoid what’s harmful for them and/or the offspring, in favor of what’s beneficial.
  • Document the subjects’ actions with history and samples.

I acknowledge that economic incentives may not be enough to get people to participate. I’m familiar with a juvenile sickle-cell study that didn’t get enough subjects despite offering free transportation and hundreds of dollars per visit. The main problem seemed to be that the additional income would be reported and threaten the caregiver’s welfare benefits.

Stop whining that your jobs are difficult, researchers. Society doesn’t owe you a job. Earn it – get yourself and the people in your organization motivated to advance science.

http://www.sciencedirect.com/science/article/pii/S014976341630731X “Experience-induced transgenerational (re-)programming of neuronal structure and functions: Impact of stress prior and during pregnancy” (not freely available)

Transgenerational effects of early environmental insults on aging and disease

The first paper of Transgenerational epigenetic inheritance week is a 2017 Canadian/Netherlands review that’s organized as follows:

“First, we address mechanisms of developmental and transgenerational programming of disease and inheritance. Second, we discuss experimental and clinical findings linking early environmental determinants to adverse aging trajectories in association with possible parental contributions and sex-specific effects. Third, we outline the main mechanisms of age-related functional decline and suggest potential interventions to reverse negative effects of transgenerational programming.”

A transgenerational phenotype was defined as an epigenetic modification that was maintained at least either to the F2 generation in the paternal lineage or to the F3 generation in the maternal lineage.

The reviewers noted that the mechanisms of transgenerational programming are complex and multivariate.  The severity, timing, and type of exposure, lineage of transmission, germ cell exposure, and gender of an organism were the main factors that may determine the consequences. The mechanisms reviewed were:

  1. Parental exposure to an adverse environment;
  2. Altered maternal behavior and care of the offspring; and
  3. Experience-dependent modifications of the epigenome.

There was a long list of diseases and impaired functionalities that were consequences of ancestral experiences and exposures. Most of the studies were animal, but a few were human, such as those done on effects of extended power outages during the Quebec ice storm of January 1998.


One intervention that was effective in reversing a transgenerational phenotype induced by deficient rodent maternal care was to place pups with a caring foster female soon after birth. It’s probably unacceptable in human societies to preemptively recognize all poor-care human mothers and remove the infant to caring foster mothers, but researchers could probably find enough instances to develop studies of the effectiveness of the placements in reversing a transgenerational phenotype.

The review didn’t have suggestions for reversing human transgenerational phenotypes, just  “..potential interventions to reverse negative effects of transgenerational programming.” The interventions suggested for humans – exercise, enriched lifestyle, cognitive training, dietary regimens, and expressive art and writing therapies – only reduced the impact of transgenerational epigenetic effects.

The tricky wording of “..reverse negative effects of transgenerational programming” showed that research paradigms weren’t aimed at resolving causes. The review is insufficient for the same reasons mentioned in How one person’s paradigms regarding stress and epigenetics impedes relevant research, prompting my same comment:

“Aren’t people interested in human treatments of originating causes so that their various symptoms don’t keep bubbling up? Why wouldn’t research paradigms be aligned accordingly?”

When reversals of human transgenerational phenotypes aren’t researched, the problems compound as they’re transmitted to the next generations.

http://www.sciencedirect.com/science/article/pii/S014976341630714X “Transgenerational effects of early environmental insults on aging and disease incidence” (not freely available)

Epigenetic effects of early life stress exposure

This 2017 Netherlands review subject was the lasting epigenetic effects of early-life stress:

“Exposure to stress during critical periods in development can have severe long-term consequences..One of the key stress response systems mediating these long-term effects of stress is the hypothalamic-pituitary-adrenal (HPA) axis..early life stress (ELS) exposure has been reported to have numerous consequences on HPA-axis function in adulthood.

ELS is able to “imprint” or “program” an organism’s neuroendocrine, neural and behavioral responses to stress..research focuses along two complementary lines.

Firstly, ELS during critical stages in brain maturation may disrupt specific developmental processes (by altered neurotransmitter exposure, gene transcription, or neuronal differentiation), leading to aberrant neural circuit function throughout life..

Secondly, ELS may induce modifications of the epigenome which lastingly affect brain function..These epigenetic modifications are inducible, stable, and yet reversible, constituting an important emerging mechanism by which transient environmental stimuli can induce persistent changes in gene expression and ultimately behavior.”

In early life, the lower brain and limbic system brain structures are more developed and dominant, whereas the cerebrum and other brain structures are less developed (use the above graphic as a rough guide). Stress and pain generally have a greater impact on the fetus, then the infant, and then the adult.


The reviewers cited 50+ studies from years 2000-2015 in the “Early Life Stress Effects in a “Matching” Stressful Adult Environment” section to argue for the match/mismatch theory:

“Encountering ELS prepares an organism for similar (“matching”) adversities during adulthood, while a mismatching environment results in an increased susceptibility to psychopathology, indicating that ELS can exert either beneficial or disadvantageous effects depending on the environmental context.

Initial evidence for HPA-axis hypo-reactivity is observed for early social deprivation, potentially reflecting the abnormal HPA-axis function as observed in post-traumatic stress disorder.

Interestingly, experiencing additional (chronic) stress in adulthood seems to normalize these alterations in HPA-axis function, supporting the match/mismatch theory.”

Evidence for this theory was contrasted with the allostatic load theory presented in, for example, How one person’s paradigms regarding stress and epigenetics impedes relevant research.


The review mainly cites evidence from rodent studies that mismatched reactions in adulthood may be consequences of early-life events. These events:

“..imprint or program an organism’s neuroendocrine, neural and behavioral responses..leading to aberrant neural circuit function throughout life..which lastingly affect brain function..”

Taking this research to a personal level:

  • Have you had feelings that you were unsafe, although your environment was objectively safe?
  • Have you felt uneasy when people are nice to you?
  • Have you felt anxious when someone pays attention to you, even after you’ve acted to gain their attention?

I assert that mismatched human feelings are one form of mismatched reactions. As such, they may be interpreted as consequences of early-life experiences, and indicators of personal truths.

If researchers can let go of their biases and Advance science by including emotion in research, they may find that human subjects’ feelings produce better evidence for what actually happened during the subjects’ early lives than do standard scientific methods of:

Incorporating this evidence may bring researchers closer to backwardly predicting the major insults to an individual that knocked their development processes out of normally robust pathways and/or induced “persistent changes in gene expression and ultimately behavior.”

https://www.frontiersin.org/articles/10.3389/fncel.2017.00087/full “Modulation of the Hypothalamic-Pituitary-Adrenal Axis by Early Life Stress Exposure”


I discovered this review as a result of it being cited in http://www.sciencedirect.com/science/article/pii/S1084952117302884 “Long-term effects of early environment on the brain: Lesson from rodent models” (not freely available)

Epigenetic effects of THC differ between female adolescents and adults

This 2017 Italian rodent study found:

“THC [delta9-tetrahydrocannabinol, the psychoactive compound of cannabis] exposure affects histone modifications in the brain of female rats in a region- and age-specific manner. Specifically, THC acts on different targets depending on the considered brain area and, remarkably, the adolescent brain is generally more sensitive to THC than the adult brain.

Adolescent exposure to THC, or to synthetic cannabinoids, induced sex-dependent brain and behavioral alterations at adulthood. In female rats, the phenotype was more complex, as both depressive-like and psychotic-like signs were present..the development of the depressive/psychotic-like phenotype is restricted to adolescent THC exposure..not only the behavioral phenotype developed after adolescent, and not adult, exposure, but also changes in both histone modifications and gene expression were more widespread and intense after adolescent treatment, further confirming a specific adolescent susceptibility.

The primary effect in the adolescent brain was represented by changes leading to transcriptional repression, whereas the one observed after adult treatment led to transcriptional activation. Moreover, only in the adolescent brain, the primary effect was followed by a homeostatic response to counterbalance the THC-induced repressive effect, except in the amygdala.”

The authors’ interpretation of the brain area results was:

“..the amygdala is more responsive in adult than adolescent animals..Since it has been established that the amygdala is activated during exposure to aversive stimuli, functioning as a “behavioral brake”, the different response between adult and adolescent animals could represent the biological bases of the adolescent propensity for risk-taking and novelty-seeking behaviors..also in adolescent humans, neuroimaging studies have shown a weaker involvement of the amygdala, and a greater contribution of the NAc [nucleus accumbens], in response to negative and positive stimuli compared to adults.”

http://www.mdpi.com/1422-0067/18/10/2094 “Chronic Δ9-THC Exposure Differently Affects Histone Modifications in the Adolescent and Adult Rat Brain”

A study of perinatal malnutrition where the paradigm excluded epigenetic inheritance

This 2017 New York/Swedish rodent study subject was the epigenetic effects on the F1 generation of maternal low protein diet during pregnancy and lactation:

“Male, but not female, offspring of LPD [low protein diet] mothers consistently displayed anxiety- and depression-like behaviors under acute stress.

Our proposed pathway connecting early malnutrition, sex-independent regulatory changes in Egr1 [an Early growth response gene], and sex-specific epigenetic reprogramming of its effector gene, Npy1r [neuropeptide Y receptor Y1 gene], represents the first molecular evidence of how early life risk factors may generate sex-specific epigenetic effects relevant for mental disorders.”


The study was purposely incomplete regarding epigenetic effects that may be transmitted from the F1 generation to a F2 generation. Similar to How one person’s paradigms regarding stress and epigenetics impedes relevant research, the paradigm continued by one of this study’s coauthors restricted inquiry into epigenetic inheritance.

How can the other coauthors respond when a controller of funding publishes the paper referenced in What is epigenetic inheritance? and otherwise makes his narrow views regarding epigenetic inheritance well-known? If the controller’s restricted views won’t allow the funding scope to extend to study a F2 generation, the experiments end, and our understanding of epigenetic inheritance isn’t advanced.

This purposely incomplete study showed that the coauthor only gave lip service to advancing science when he made statements like:

“Further work is needed to understand whether and to what extent true epigenetic inheritance of stress vulnerability adds to the well-established and powerful influence of genetics and environmental exposures.”

https://www.nature.com/articles/s41598-017-10803-2 “Perinatal Malnutrition Leads to Sexually Dimorphic Behavioral Responses with Associated Epigenetic Changes in the Mouse Brain”

Parental lying thwarted both their children and researchers

This 2017 German human study explored the relationship between birth stress and handedness. The authors summarized previous research which, among other points, estimated epigenetic contributions to handedness as great as 75%.

The study hit a snag in its reliance on the sixty participants (average age 24) completing, with the assistance of their parents and medical records, a 24-item questionnaire of maternal health problems during pregnancy, substance use during pregnancy, and birth complications. The subjects didn’t provide accurate information. For example:

  • Only one of the subjects reported maternal alcohol use during pregnancy. An expected number would have been 26.
  • None of the subjects reported maternal mental illness during pregnancy. An expected number would have been at least 7.

The subjects’ parents willingly misled their children about facts of their child’s important earliest development periods. This is unethical to the children in that once it is recognized, it diminishes or destroys the society among family members. This study’s example is also of general interest to anyone who values not being lied to, like me.

As I mentioned on the Welcome page, lies and omissions ruin the standard scientific methodology of surveying parents and caregivers. The absence of evidence greatly increased the difficulty for researchers in determining causes of epigenetic effects still present in the subjects’ lives.

The parental lying is again unethical in that it diminished or destroyed the society between the sources of information – the research subjects – and the users of the information. It adversely affected anyone who values evidence-based research. The research hypothesis itself was worthwhile based on the prior studies cited and elsewhere such as Is what’s true for a population what’s true for an individual?.

http://www.tandfonline.com/doi/full/10.1080/1357650X.2017.1377726 “DNA methylation in candidate genes for handedness predicts handedness direction” (not freely available)