"A life of strength" eggs, for the offspring, strive to repair radiation-damaged sperm DNA

Nearly 80% of genetic mutations in humans occur in the paternal germline, and radiation damage is a major cause
of sperm mutations.
In recent years, male reproductive ability has declined, sperm concentration and motility have declined significantly, and more scholars have proposed that direct or indirect exposure to the electromagnetic field of mobile phones and Wi-Fi may be the main environmental factors
for the decline of male sperm count and motility.
Radiation damage to mature sperm cannot be repaired and is passed on to offspring
.
Instead, the female eggs either repair the damage accurately or are eliminated when the damage is too severe and the radiation damage is not passed on
.
However, when an egg is fertilized with a radiation-damaged sperm, the maternal repair protein provided by the egg attempts to repair the paternal damaged DNA and ensure the health
of the fertilized egg.

Radiation exposure of the father in the first 6 months of conception increases the prevalence of leukemia and lymphoma in offspring

Scientists have observed a 10-fold higher prevalence of childhood leukemia near the Sellafield nuclear power plant in the United Kingdom than in other regions, and a higher relative risk of non-Hodgkin lymphoma, particularly in children
whose fathers had high radiation doses recorded before pregnancy.
Dr.
M.
J Gardner of the University of Southampton found through his investigation that the increased incidence of leukemia in children near Sellafield, particularly non-Hodgkin lymphoma, was associated with
the father's occupation and external doses of systemic penetrating radiation recorded during work in a factory before pregnancy.
This association can statistically explain the observed territorial overreach
.
This result suggests that the effects of ionizing radiation on fathers may lead to leukemia and lymphoma in their offspring
.
This has important potential implications
for radiobiology and the protection of radiation workers and their children.

Figure 1 Research results (Source: [1])

From Chernobyl 36 years ago, explore the effects of radiation on future generations

In April 1986, Chernobyl struck one of the worst nuclear disasters
in human history.
Thirty-six years later, scientists are still exploring the effects of
radiation on plant workers, nearby residents, and their descendants.
The National Cancer Institute of the United States concentrated on the genomes of 130 children born in 1987~2002 who were directly experienced in the Chernobyl event, and their parents or residents near Chernobyl, or members of the team responsible for cleaning up the disaster, had direct exposure to radiation
.
In the end, they found that the children of the survivors had no more
DNA mutations than members of the control group whose parents had never been exposed to radiation.
In other words, the health effects of the radiation from the Chernobyl event on the next generation are almost negligible
.
Stephen J.
Chanock, corresponding author of the study, said: "Our findings are reassuring to survivors of the Fukushima accident
.
”

Figure 2 Research results (Source: [2]) Will the sperm DNA damage caused by radiation be passed on to offspring?

It is not uncommon for the scientific community to come up with conflicting results, but this divergence is due to a lack of in-depth exploration
of the mechanism.
Whether a father's radiation exposure can affect the child is one of
the long-standing questions in radiation biology.
Nearly 80% of genetic mutations in humans occur in the paternal germline, as radiation damage to mature sperm cannot be repaired but passed on to offspring
.
Instead, the female eggs either repair the damage accurately or are eliminated when the damage is too severe and the radiation damage is not passed on
.
However, when an egg is fertilized with a radiation-damaged sperm, the maternal repair protein provided by the egg also attempts to repair the paternal DNA
.
To this end, Professor Björn Schumacher and his research team used the classical model organism Caenorhabditis.
elegans delved into the genetic mechanisms
of radiation-induced DNA damage.

Figure 3 Research results (Source: [3])

Ionizing radiation exposure in male Caenorhabditis elegans leads to DNA double-strand breaks (DNA dsb) in mature spermatozoa, causing de novo mutations (DNMs) and chromosomal aberrations, leading to F1 genomic instability and death of transgenerational embryos
.
Radiation-damaged sperm carry DNA fragments into oocytes for the fertilization process
.
Ooocytes provide an error-prone polymerase (TMEJ) mechanism to repair paternal DNA radiation damage, causing random ligation of chromosomal parts that lead to various chromosomal aberrations
.

In offspring, these aberrant chromosomes undergo periodic breaks, but this break can no longer be repaired
.
Because broken chromosomes are protected by proteins (i.
e.
, histones), they cannot be accurately repaired
.
Specific histones HIS-24 and HPL-1 tightly wrap the long strands of DNA, and the repair protein cannot reach the
break.
When these histones are removed, paternally inherited radiation damage is completely eliminated and viable offspring
can be produced.
In summary, paternal exposure to ionizing radiation restricts DNA repair pathways through heterochromatin resulting in death in transgenerational embryos
.

Figure 4 Schematic model of cross-generational effects of male exposure to ionizing radiation (Source: [3]) Professor Björn Schumacher said: "Genomic aberrations, particularly structural variations in chromosomes, are thought to increase the risk of
diseases such as autism and schizophrenia.
This means that human mature sperm need special protection from radiation damage, and damaged mature sperm should not be used for conception
.
This damage can be caused during radiation or chemotherapy, so it poses a risk
within a two-month period of producing new sperm to replace the damaged sperm.
This is because newly produced sperm have the ability to repair damage accurately compared to
mature sperm.