Toll like receptors in Chronic Lymphocytic Leukaemia

How stress can have an impact on

epigenetics of sperm

introduction Stress is something that everyone in the world has experienced at one point of their

human life. Stress is something that can come from anything and in some cases

extremely unavoidable. Stress is something that can affect people in any field or

work it can also have an effect on humans’ body parts as well as animals. The word

stress means “pressure or tension exerted on a material object’ by definition. In this

literature review I will be talking about the effects of stress on epigenetics, as there

are reports talking about epigenetics and its link to sperm. In particular the studies

show that micro- RNAs can be passed on via sperm and these can then imprint the

foetus with stress factors.

What is Epigenetics? What is epigenetics, well epigenetics is the study of biological mechanism that switch

genes and on and off. To get an idea of what epigenetics you need know the basic

fundamentals of the DNA and how it is comprised, and the bases involved.

Cells are extremely fundamental parts of every human being and living thing. All the

cells contain deoxyribonucleic acid, also known as DNA which contain instructions to

direct their activities. DNA is made from more than 3 billion different nucleotide

bases. There are four main types of bases that come together to create DNA. These

are adenine, cytosine, guanine and thymine. They are more commonly known as A,

C, G and T. there is an extra bases for RNA which is uracil (U) and this takes the

place of thymine (T). It is very important the way the sequences of the bases are

made from as the sequences determine the way we are made. It is very interesting

that our DNA sequences are most similar to that of a chimpanzee but is different due

to the way that sequences that makes us human. Within the 3 billion bases, there

are about 20,000 genes. Genes are specific sequences of bases that provide

instructions on how to make important proteins – complex molecules that trigger

various biological actions to carry out life functions. (What is Epigenetics? (2019)

What I hope to find

I hope to find in this literature review is a link between sperm and stress and also the

effects it can have being long-lasting or just temporary. I also hope to find what

different experiment procedures that they had to go through in order to get the link

that stress can be imprinted into the foetus of an unborn child.

Article that support: How stress can have an impact on epigenetics of sperm According to an article by Katherine J. Wu who is a Digital Editor at PBS NOVA and

Story Collider producer. She holds a Ph.D. in Microbiology and Immunobiology from

Harvard University. She states in her article about “Dads Pass on More Than

Genetics in Their Sperm” that your body will remember and possibly pass the

consequences onto your kids. In the past several years there have been mounting

evidence that has shown that sperm can take note of a father’s lifestyle decisions

and transfer this baggage to offspring. There have been two complementary studies

by scientist that tell us how this has been done in detail. (katherine. J wu (2018)

As the sperm travels through the male reproductive system, they carry genetic cargo

that alters the sperm before ejaculation. These modifications of the sperm not only

communicate the father current state of mind and well-being, but they could also

have a drastic impact on the viability of the future offspring. On average roughly

there are 76,000 children born as the result of assisted reproductive techniques,

which mostly involve a type of invitro fertilisation (IVF). For an invitro fertilisation to

take place you need to get an egg from a female and sperm out of the human body,

the transfer then results in a fertilised egg which is embryo. The embryo is then

placed inside the female’s uterus. There are different types of invitro fertilisation

(IVF) that exist, in some cases male infertility can occur which can cause the sperm

to struggle to swim. In these cases, sperm is then surgically extracted from the

testes or the epididymis which is a long-convoluted duct that cradles each testis.

(katherine. J wu (2018)

After the sperm is produced in the testis, they go through a long and harrowing

journey through the epididymis, which in a human male is roughly 6 meters long

)

when stretched in a line on to storage. The sperm wander in the epididymis for two

weeks before end of the path where they are fully motile. When the sperm is fully

mature it can be dumped on the egg that is waiting to be fertilised. Sperm that taken

from the testis and epididymis must be injected directly into the egg with a very fine

needle. Whatever the source of the sperm these techniques have been proven to

have birthed healthy children in four decades of successful procedures. Scientist

know that genes are not the whole package. Over the course of a single human life

time, the way our genomes where originally written have stayed the same, however

when and why genetic instructions are followed can majorly change without altering

itself. This is called epigenetics this explains why genetically looking individuals know

as twins can still act in different ways and factors like stress and dieting are capable

of cranking up our genes. (katherine. J wu (2018)

One of the most powerful tools in epigenetics is a molecule called small RNAs. Small

RNAs are capable of concealing genetic information from cellular information from

cellular machinery that carry out their instructions, as a result of this they can ghost

genes out of existence. (katherine. J wu (2018)

In most of the article it mostly relays the idea that sperm is able to carry information

that most people would not think that sperm can carry such as stress, it also goes on

to say in the first part of the article it is mainly the male sexual reproductive system

that imprints the foetus with

In another study two scientist Upasna Sharma and Colin conine both working under

Oliver rando, who is a professor of biochemistry at the university of Massachusetts

Medical school, where some of the researches to report the findings in 2016. In their

work they noted that in mice with immature testicular sperm contains DNA which is

identical to that of a mature sperm can relay different information. They found that

small RNAs can undergo small post testes information and gain information from the

testes of the father’s physical health or lack of health after they are born. (katherine.

J wu (2018)

To solve the mystery, they decided to track the composition of small RNAs within the

mouse sperm, when they fled the testes all the way through the epididymis. Her

)

colleagues then isolated the sperm of several different aged mice, including the ones

that were currently developing testes and those entering the early part of epididymis

and the late stages epididymis. Sharma was surprised to find that many small RNAs

seemed to be discarded or destroyed when they entered the epidermis. then the

Newley vacated sperm reacquired epigenetic information that reflected the father

state of mind and being. (katherine. J wu (2018)

The fact that they did two studies on the subject shows that the first one had to be a

success I order to continue to the next study, also they used a range of variables in

the experiments that did using a variety of mice at different age groups with different

maturities shows that the results that the sperm carries out the information of stress

markers during the early stages of development of an offspring and furthermore

epigenetics also helps in the passing of genetic information such as a poor diet

requirements and most importantly in this situation stress.

There was only one possible source for the small RNA reacquisition: the cells of the

epididymis. Which meant that cells outside of the sperm were transmitting

information into future generations. The epidermis is the least studied organ in the

body,” says Rando, who was senior author on both papers. “And it turns out this tube

that no one ever thinks about plays a central role in reproduction.” To confirm that

the epididymis was the culprit, Sharma’s team added a chemical marker to a set of

small RNAs in the epididymis and tracked their migration. As they suspected, tiny

shipments of RNAs popped off of cells in the epididymis and fused with the sperm.

Each stealthy swimmer then bore these epigenetic elements all the way to its final

union with the egg. It seemed that sperm at different points along the reproductive

tract had the same genetics, but not the same epigenetics. Was this difference big

enough to matter? Colin Conine, who led the second of the two new studies, next

tested if using immature sperm would have noticeable effects on the offspring of

mice. He and his colleagues extracted sperm from the testes, early epididymis and

late epididymis and injected them into eggs. All three types of sperm were able to

fertilize eggs. However, when Conine transferred the resulting embryos into mouse

surrogates, none derived from early epididymal sperm—the intermediate stage

devoid of most small RNAs—implanted in the uterus. The least and most mature

sperm of the bunch were winners—but somehow, those in the middle were burning

out, even though all their genes were intact. (katherine. J wu (2018)

I can say after reviewing the article with two studies in how stress can affect the

epigenetics of the sperm and pass on characteristics such as dieting and stress. I

can positively say that there is a connection between the two as there are arrange of

studies done by professionals that tell us this furthermore, I can say that there are

trends in the research with all of the research in this topic about the small RNAs

having an big influences on stress and that in particular the father can pass on

information via the male reproductive system that in turn will go to the offspring

causing the offspring to get these bits of information of traumatic experience in

bedded into them.

The reason why I choose the topic stress is ,because it is what everyone

experiences in day to day life, but the reason why I chose epigenetics and stress on

comes sperm is because there are lots of studies going on in the recent years that

test this theory and a lot of the articles conclude there is a correlation between stress

and the epigenetics of the sperm which could lead to the stress being imprinted in

the foetus. Another reason why this is important is because the world we live in now

is more stressed than ever meaning that up coming generations could be passing on

this trait to the next offspring.

Bibliography

What is Epigenetics? (2019). A Super Brief and Basic Explanation of Epigenetics for Total Beginners. [online] Available at: https://www.whatisepigenetics.com/what-is-epigenetics/ [Accessed 2 Mar. 2019].

katherine. J wu (2018). Dads Pass on More Than Genetics in Their Sperm. [online] Smithsonian. Available at: https://www.smithsonianmag.com/science-nature/dads- pass-more-genetics-their-sperm-180969760/ [Accessed 2 Mar. 2019].