View Full Version : Epigenetics"...without any change in the genes themselves."


mildadhd
01-08-13, 12:59 PM
There is a new and rapidly growing science that focuses on how life experiences influence the function of genes.

It's called epigenetics.

As a result of life events,

chemicals attach themselves to DNA and direct gene activities.

The licking of a rat pup by the mother in early hours of life turns on a gene in the brain that helps protect the animal from being overwhelmed by stress even as an adult.

In rats deprived of such grooming,

the same gene remains dormant.

Epigenetics effects are most powerful during early development and have now been shown to be transmittable from one generation to the next,

without any change in the genes themselves. (*15)

Environmentally induced epigenetic influences powerfully modulate genetic ones.



-Gabor Mate M.D., In The Realm Of Hungry Ghosts, P204.





i!i

Note (*15)

M.J Meaney," Maternal Care, Gene Expression, and the Transmission of Individual Differences in Stress Reactivity Across Generations," Annual Review of Neuroscience 24 (2001):1161-92



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mildadhd
01-08-13, 01:13 PM
Maternal care, gene expression, and the transmission of individual differences in stress reactivity across generations.


Abstract
Naturally occurring variations in maternal care alter the expression of genes that regulate behavioral and endocrine responses to stress, as well as hippocampal synaptic development. These effects form the basis for the development of stable, individual differences in stress reactivity and certain forms of cognition. Maternal care also influences the maternal behavior of female offspring, an effect that appears to be related to oxytocin receptor gene expression, and which forms the basis for the intergenerational transmission of individual differences in stress reactivity. Patterns of maternal care that increase stress reactivity in offspring are enhanced by stressors imposed on the mother. These findings provide evidence for the importance of parental care as a mediator of the effects of environmental adversity on neural development.


http://www.ncbi.nlm.nih.gov/pubmed/11520931

Dizfriz
01-08-13, 02:03 PM
Maternal care, gene expression, and the transmission of individual differences in stress reactivity across generations.


Abstract

Naturally occurring variations in maternal care alter the expression of genes that regulate behavioral and endocrine responses to stress, as well as hippocampal synaptic development. These effects form the basis for the development of stable, individual differences in stress reactivity and certain forms of cognition. Maternal care also influences the maternal behavior of female offspring, an effect that appears to be related to oxytocin receptor gene expression, and which forms the basis for the intergenerational transmission of individual differences in stress reactivity. Patterns of maternal care that increase stress reactivity in offspring are enhanced by stressors imposed on the mother. These findings provide evidence for the importance of parental care as a mediator of the effects of environmental adversity on neural development. http://www.ncbi.nlm.nih.gov/pubmed/11520931


Peripheral This seems to be more about maternal (post natal) care and not much about epigenetics. The whole article is behind a paywall but judging from the abstract, It doesn't seem to be much about prenatal neurological development or epigenetics to any degree but more about the importance of parental care in the postnatal environment.

I don't think anyone disputes the powerful impact of parental care on neurological development but there are a number of questions on the specifics.

Dizfriz

ConcertaParent
01-08-13, 02:39 PM
Maternal care is just one example of the importance of epigenetic influences. Twin studies have produced evidence of epigenetic influence in humans. For example,
Epigenetic differences arise during the lifetime of monozygotic twins (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1174919/).
Abstract

Monozygous twins share a common genotype. However, most monozygotic twin pairs are not identical; several types of phenotypic discordance may be observed, such as differences in susceptibilities to disease and a wide range of anthropomorphic features. There are several possible explanations for these observations, but one is the existence of epigenetic differences. To address this issue, we examined the global and locus-specific differences in DNA methylation and histone acetylation of a large cohort of monozygotic twins. We found that, although twins are epigenetically indistinguishable during the early years of life, older monozygous twins exhibited remarkable differences in their overall content and genomic distribution of 5-methylcytosine DNA and histone acetylation, affecting their gene-expression portrait. These findings indicate how an appreciation of epigenetics is missing from our understanding of how different phenotypes can be originated from the same genotype.
This seems to be more about maternal (post natal) care and not much about epigenetics.

Amtram
01-08-13, 03:44 PM
I think the big problem people have in wrapping their heads around the idea of epigenetics is that it encompasses multiple mechanisms of gene expression from pre-conception to death. It's an ongoing process.

If an adult is exposed to a chemical, or pathogen, or external force that causes an alteration in the DNA of his/her germ cells (sperm or egg), that is epigenetic.

If, after conception, the instructions of the DNA are interpreted properly by the RNA and executed perfectly by the proteins, that's epigenetics.

If, after conception, the instructions of the DNA are interpreted improperly by the RNA and the proteins carry out the RNA's instructions, that's epigenetics.

If, after conception, the instructions of the DNA are interpreted properly by the RNA, but executed improperly by the proteins, that's epigenetics.

If, after birth, cells multiply exactly as outlined by the instructions that created the initial cell growth, that's epigenetics.

If, after birth, cells multiply in a different way from the original instructions, that's epigenetics.

Cells lost to apoptosis that are replaced with nearly identical cells is epigenetics.

Cells lost to apoptosis that are replaced with different cells is epigenetics.

Genetic instructions that are passed on to offspring are epigenetics.

Genetic instructions that are changed because of exposure to a methylating agent is epigenetics.

Epigenetics do not change the DNA of a living individual, only the gene expression of that individual. Epigenetics can change the DNA of the living individual's sperm or egg cells, resulting in a new heritable trait, or a potential change in gene expression. Or nothing that makes any difference.

Epigenetics is what happens between DNA and the production of new cells. Germ cells that are produced by this process can be changed by it, and thereby have altered DNA for the next generation.

But DNA is the foundation. It stays the same, but what is made from it can change, and that's epigenetics - making things from the DNA.

tudorose
01-08-13, 05:45 PM
Is it that the instinct genes DON'T turn on for us and that we need to be taught the things that others do and know instinctively ie social skills etc?

TygerSan
01-08-13, 05:49 PM
"without any change to the genes themselves"

That doesn't quite get the nature of epigenetics as I understand it. . . The fact of the matter is that the expression of the genes, *do*, in fact, change.

Genes code for protein. Changing the genetic code is only one way in which the proteins are expressed.

In epigenetics, the genetic sequence itself doesn't change, but the way that sequence is read does. So it's sort of like a corrupt disk. . . epigenetics may knock out/inactivate certain sectors, or it may amplify the production that protein. So while the genes themselves are unchanged, the protein environment that regulates them is changed drastically.

Amtram
01-08-13, 07:14 PM
Some of the problem stems from people not understanding how many different components are involved and thinking that the general term "genes" covers it all. "DNA, RNA, chromosomes, genes, you know, all the same thing. . ." I know several people IRL who don't know there's a difference, so there's obviously some confusion.

mildadhd
01-08-13, 09:01 PM
http://www.ncbi.nlm.nih.gov/pubmed/11520931


Peripheral This seems to be more about maternal (post natal) care and not much about epigenetics. The whole article is behind a paywall but judging from the abstract, It doesn't seem to be much about prenatal neurological development or epigenetics to any degree but more about the importance of parental care in the postnatal environment.

I don't think anyone disputes the powerful impact of parental care on neurological development but there are a number of questions on the specifics.

Dizfriz


Dizfriz,

I`m glad you asked the question.

I`m trying to learn more about these principles.

Not sure this is what you asking but will look for more when I have time.

Opinion.





Childhood Experience and the Expression of
Genetic Potential: What Childhood Neglect Tells
Us About Nature and Nurture
BRUCE D. PERRY


MAJOR PROCESSES OF NEURODEVELOPMENT


1. Neurogenesis: The brain develops from cells present in the embryo in the

firstweeks following conception.

From these few undifferentiated cells,

come billions of nerve cells and trillions of glia.

The vast majority of neurogenesis,

the “birth” of neurons,

takes place in utero during the second and third trimester.

At birth,

the vast majority of neurons used for the remainder of life are present.

Few neurons are born after birth,

although researchers have demonstrated recently that neurogenesis

does take place in the mature brain (Gould et al., 1999).

Neurogenesis in the mature brain may be one of the important physiological

mechanisms responsible for the brain’s plasticity (i.e., capacity to restore function) following injury.

Despite being present at birth,

most neurons have yet to organize into completely functional systems.

The billions of neurons present at birth need to further specialize and connect

with other neurons in order to create the functional neural networks of the

mature brain.

http://centerforchildwelfare2.fmhi.usf.edu/kb/ChronicNeglect/ChildExperience.pdf




Key Processes in Neurodevelopment
Neurogenesis
Migration
Differentiation
Apoptosis (cell death)
Arborization
Synaptogenesis
Synaptic Sculpting
Myelination

http://www.trcnconsortium.com/ACYF_ppts/Perry.pdf