Nature PLUS nurture make a (well)being.

July 21, 2015

Epigenetic changes in brain development. Nature and nurture work together.

 

The old adagio nature vs nurture is shaky.

 

“The environment is a critical player in how your genetic endowments work” (Yehuda)

 

and the development of a human being is not anymore a decision between “nature vs nurture” (genes or upbringing) but an interplay between the two: development is driven by a continuous interaction between biology (= DNA code or genetic predispositions) and ecology (=social and physical environment).

 

Epigenetics is the science that studies the fairly stable alterations in gene expression (‘turning on’ of genes) that arise during development, differentiation and growth under the influence of the environment.

 

Among the several studies of epigenetics in the process of a human growth is the development of the human brain and how this is affected by external conditions.

The billions of neurons in a single brain have the same DNA sequence but their diverse functions are created by epigenetic programming during pre- and postnatal development and possibly throughout life. Epigenetic mechanisms have the care of brain development, differentiation and maturation and are at the base of complex behaviors like memory and learning.

 

The most studied type of “external conditions” from the environment during brain development has been the study of stressors or stimuli that entice a “fight-flight-freeze” response from the organism.

 

Early life stress: certain conditions of life environment in the early stages of development can cause epigenetic programming of critical genes involved in regulating the stress response.

 

The stress response is carried out by the hypothalamus-pituitary-adrenal axis in the brain. Consequent to a stressor, the amygdala in the center of the brain sends a message of alarm to the hypothalamus to release a neurotransmitter (corticotropin releasing hormone) to the pituitary gland which in turn sends a message (adrenal corticoptic hormone) to the adrenal glands, which then release adrenaline, noradrenalin and later cortisol. This chain of events results in an

 

     increase of heart rate, breathing efficiency, blood pressure,

    decrease in digestive and reproductive functions etc.

 

which is the stress response: either fight the danger or fly from it. (reference to another blog).

 

 

Some abnormal conditions of early life environment (lack of nurturing, neglect, abandonment, abuse) can provoke changes in DNA methylation, facilitating activation of critical genes involved both in regulating the stress response and in reducing expression of hormones that regulate neurodevelopment, neuroplasticity and neuronal functions.

 

These dysregulated responses to abandonment, abuse and neglect of a child can result in a distorted behavioral reaction and diseases in childhood and adulthood:

 

    ~ early life: anger, despair, detachment, temporary delay in intellectual development;

   

    ~ adulthood: same lack of care to the future generation (perpetuating the damage),

increased stress response activity, increased risk of depression or anxiety, risk of cognitive impairment, social and emotional difficulties, risk of psychiatric and neurodegenerative disorders and physical diseases (obesity, osteoporosis and cardiovascular problems).

 

The good news is that such types of epigenetics responses can be undone by changing the nurturing environment (but how late can this be done?).

 

Offering the child the best caring enviornment will insure a safe place for proper development and preparation for his/her offspring to be taken care in the same healthy way.

 

 

 

 

 

References

Caspi A, McClay J, Moffi t TE, Mill J, Martin J, Craig IW, et al.2004 Role of Genotype in the cycle of violence in maltreated children.Science 2004; 97:851–4.

 

Graff, J. , Kim, D., Dobbin, M.M.,Tsai, L. Epigenetic Regulation of Gene Expression in Physiological and Pathological Brain Processes 2011, Physiol Rev 91: 603–649

 

Hooper, r. 2006 Men inherit hidden cost of dad’s vices, New Scientist, 4-1-2006

 

Jaenisch R, Bird A. 2003 Epigenetic regulation of gene expression: how the genome integrates intrinsic and environmental signals. Nature Genet 33: 245–254.

 

Learn.Genetics, Genetic Science Leanring center, in: <http://learn.genetics.utah.edu/content/epigenetics/>

 

McGowan PO, Sasaki A, D’Alessio AC, Dymov S, Labonte B, Szyf M, Turecki G, Meaney MJ. 2009 Epigenetic regulation of the

glucocorticoid receptor in human brain associates with childhood abuse. Nat Neurosci 12: 342–348, 2009.

 

Meaney MJ, Szyf M. Environmental programming of stress responses through DNA methylation: life at the interface between a dynamic environment and a fixed genome. Dialogues in ClinicalNeuroscience 2005; 7:103–23.

 

Murgatroyd C, Patchev AV, Wu Y, et al. 2009 Dynamic DNA methylation programs persistent adverse effects of early-life stress. Nat Neurosci. 2009;12(12):1559–1566

 

Roth TL, Lubin FD, Funk AJ, Sweatt JD. 2009 Lasting epigenetic influence of early-life adversity on the BDNF gene. Biol Psychiatry. 65(9):760–769

 

Shonkoff, J.P., Andrew S. Garner, and THE COMMITTEE ON PSYCHOSOCIAL ASPECTS OF CHILD AND FAMILY HEALTH, COMMITTEE ON EARLY CHILDHOOD, ADOPTION, AND DEPENDENT CARE, AND SECTION ON DEVELOPMENTAL AND BEHAVIORAL PEDIATRICS 2012The Lifelong Effects of Early Childhood Adversity and Toxic Stress, Pediatrics129;e232

 

Spinney, L. 2010 Born scared: How your parents’ trauma marks your genes, New Scientist,

24/11/2010

 

Sun-Wei Guo 2009 Epigenetics of endometriosis Mol. Hum. Reprod. 15, 10, 587-607

 

Thomson, H. 2015  First evidence of how parents’ lives could change children’s DNA, New Scientist, 4 June 2015

 

Wikipedia, 2015, https://en.wikipedia.org/wiki/Epigenetics

 

Zhang Xiang, Shuk-Mei Ho 2011 Epigenetics meets endocrinology J Mol. Endocrinol. 46, R11-R32

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