-Summary:
Male infertility is a complicated health problem that is on the rise and affects one in 20 couples.
The role of the environment in causing disease has been highlighted and it has been inferred that epigenetics play a leading role in the maturation and function of abnormal sperm.
-Discussion:
Several studies have indicated that there are undesirable changes in the epigenetic profiles of men who undergo fertility treatment.
Although extensive research has been conducted in this area in recent years, the underlying cause of the steady decline in male fertilization potential remains unclear.
In addition, there is growing evidence that both genetic and environmental factors contribute equally to alterations in the epigenetic mechanisms that regulate fertilization, placental development, and fetal development.
Epigenetics is an information system found in DNA to control which genes are accessible, active or inactive.
Each cell in your body has essentially identical DNA, but they have different patterns of expression. They look different, their phenotype is different, and the reason for this is epigenetics.
In some cells, the «g» gene is activated, while in others it is deactivated. There is a pattern of expression across the genome, which is what epigenetics does.
The reason why epigenetics is important in fertility is that it is thought to provide a biomarker for possible problems with sperm function and early embryo development.
Epigenetic mechanisms can be associated with reproductive fertility, and even have transgenerational effects.
Epigenetics is an inherited modification of the DNA bases and chromatin proteins that does not alter the sequence of the base pair, but can improve or suppress its transcription.
Epigenetics is a normal phenomenon of gene regulation that is involved in human development and cell differentiation.
In fact, each cell type in the body is genetically identical but needs to differentiate phenotypically to support a normally functioning human body: neurons, skin, etc.
Several external factors can influence the function of genes in an epigenetic way, both positive and negative, including aging, exposure to the environment, diseases such as cancer, diet and even exercise.
-Conclusions:
Disorders in genetic imprinting
These epigenetic marks are established in the germ line and are generally maintained by mitotic divisions.
Sometimes these imprint genes are not properly methylated and cause serious genetic diseases, such as Prader-Willi syndrome, Beckwith-Wiedermann syndrome, Silver-Russell syndrome and Angelman syndrome.
The imprinting genes, it is very clear that they are critical for early brain development.
In addition to causing neurological problems in children, incorrect imprinting can affect very early development and make conception difficult.
As a factor in Male Infertility
Several studies have examined specific genomic imprinting locus to determine if aberrant DNA methylation at these sites is associated with infertility.
The imprints, which are important during spermatogenesis, have compared the differential methylation region (DMR) of the paternally methylated H19 locus and the DMR of the non-methylated MEST locus in sperm from fertile and infertile men.
A loss of methylation in H19 has been observed in men with poor semen parameters, and a decrease in sperm count.
Importance in early development:
The importance of proper DNA methylation for both male fertility and IVF outcome has been proven.
This essential epigenetic mark has an enormous utility in maintaining the activation and repression of genes. Inappropriate methylation clearly results in abnormal phenotypes.
The development of diagnostic technologies that recognize these markings could greatly improve the outcome of IVF and at the same time, accurately diagnose the fertility status of the man.
The critical changes that lead to infertility can be identified by examining the entire genome and epigenome in empirical studies.
It is necessary to determine the mechanisms of environmental effects in the manipulation of epigenetic marks, without changing the inheritance of the nucleotides.
Massive DNA sequencing or next generation sequencing (NGS) is the most advanced sequencing analysis technology. It allows in a single test to analyze a gene, several genes (panels) or the entire exome in a reduced time and cost.
The epigenome in germ cells can assist in the production of normal gametes from other body tissues through PIs (adult cells genetically reprogrammed to behave like embryonic stem cells) or isolated somatic cells, originating from the gonads.
Some cases of infertility are attributed to epigenetic events of spermatogenesis such as chromosome condensation.
The genomic packaging, in the nucleus of the spermatids or the presence of retrotranspositions and methylation has a linear relationship with the reduction of sperm motility.
In humans, transposons induce insertion mutations, and genomic instability that results in the variation of gene expression, producing genetic innovations.
In the beginning of spermatogenesis, they can damage chromatin, to avoid this, they are methylated, those transposons.
References:
-Epigenetics and fertility Volume 7 Issue 3 – 2019 Farkhondeh Pouresmaeili Medical Genetics Department, Faculty of Medicine hahid Beheshti University of Medical Sciences, Iran .
-Geutjes E, Bajpe P, Bernards R. Targeting the epigenome for treatment of cancer. Oncogene’2012, 31(34): 3827-3844, August 23, 2012.
Keywords:
epigenetics and fertility, epigenetics and male infertility, DNA methylation, transposons and epigenetics, environmental factors and epigenetics, oligozoospermia and epigenetics, teratospermia and epigenetics, azoospermia and epigenetics
Spanish 
English