to the odor acetophenone . Additionally , the region of the brain to which this odor receptor sends signals was enlarged compared to controls .
The problem here is that this contradicts what we currently know about the process of embryogenesis . After fertilisation of an egg by a sperm , almost all the epigenetic marks on the genome are erased and there is widespread reduction in the amount of heterochromatin . This is essential since cells of the embryo must be totipotent – and have the ability to not only divide countless times but also differentiate into any tissue of the body , which means that all of the genome must be equally accessible . Yet somehow epigenetic marks acquired during the lifetime of the parent mice ( F0 ), are transferred onto the genome of their sperm or eggs during their lifetime and then transmitted to their children ( F1 ). So experiences can cause live-updating , if you will , of our epigenetic markers so that subsequent generations are better prepared for their environment .
So if the epigenetic markers are erased , how can they be transferred ? Well current thinking is that RNAs , stably bound inside protein complexes can be transferred via gametes , and so even after the epigenetic markers are erased , RNA complementary to the relevant DNA sequences – like an odor receptor for example – may guide the addition of epigenetic markers to the sequences which they bind . It is important to note though , that while the role of RNAs in epigenetic silencing is already established , solid evidence for its role in transgenerational epigenetic inheritance in mammals hasn ’ t yet been found .
In any case , this has big implications for human health . Nutritional conditions during pregnancy are one of the most heavily investigated topics and though not truly transgenerational ( as the baby is already conceived ), these forms of inter-generational epigenetic modification do exist .
The thinking here is that poor nutritional conditions during pregnancy may influence metabolism and health of children far later in their lives , potentially adapting the embryo to an environment with low resources after birth . This so called “ thrifty phenotype ” has anecdotal evidence in humans . During the Dutch famine at the end of WWII , babies exposed to famine during gestation had a poorer glucose tolerance during their lives than those born the year before the famine . Studies have found babies born of famine exposed mothers had more stored fat , and this occurred even among the grandchildren of famine mothers .
As research into epigenetics continues to increase and we begin to understand the rules that govern the epigenetic modification of DNA we will be faced with new possibilities for fighting and preventing disease . If we discover that our self-imposed environment , diet or lifestyle can have prominent transgenerational effects then we will need to take better care of ourselves don ’ t you think ?
Joe Sheppard graduated from Cellular and Molecular Neuroscience masters program 2016 .
References : [ 1 ] Fraga et . al . PNAS 2005 ; copyright statement ‘ Copyright ( 2005 ) National Academy of Sciences ’ [ 2 ] http :// elmhurst-titan . com / twin-sisters-96-share-secrets-longevity / [ 3 ] Dias BG , Ressler KJ . Parental olfactory experience influences behavior and neural structure in subsequent generations . Nat Neurosci . 2014 Jan ; 17:89-96 . [ 4 ] For a free and exhaustive resource on epigenetics see here : http :// www . cell . com / cell / collections / transcription-epigenetics
Book Recommendations !
The creators of the next science read ! recommend the following books for your
Michael - The Gene : An Intimate History by Siddhartha Mukherjee Gizem - Surely You ' re Joking , Mr . Feynman ! by Richard Feynman Steffi - The Chemistry of Death by Simon Beckett Nastia - The Double Helix : A Personal Account of the Discovery of the Structure of DNA by James Watson Selina - Virolution by Frank Ryan Johanna - The Selfish Gene by Richard Dawkins Ann-Christin - Psychiatry as Cognitive Neuroscience : Philosophical Perspectives edited by Matthew R . Broome & Lisa Bortolotti
22 | NEUROMAG | November 2017