Chinese scientists have discovered a gene associated with infertility in humans.

One of the genes coding for the FSIP2 protein is responsible for the development of spermatozoa, particularly for the formation of the fibrous sheath surrounding the axoneme. The fibrous sheath determines the flexibility and strength of the spermatozoon's tail, ensuring its stability during movement and its ability to perform wave-like motions, which are necessary for the effective movement of the spermatozoon towards the egg. Similarly, the flagellum ensures the movement of the male reproductive cell through the female reproductive system to the egg. Scientists have found that in men with abnormalities in the FSIP2 gene, the spermatozoa's flagellum was shortened, twisted, or exhibited other anomalies that prevented normal motility. According to statistical data, such disorders can be observed in 5 to 7% of men suffering from infertility, highlighting the importance of this discovery for medical practice.

Research Methodology

To study the mutations of the FSIP2 gene more precisely, Chinese researchers from the Women and Children's Medical Center (Guangzhou), led by Na Li, PhD, and Lin Sun, PhD, conducted a series of experiments on laboratory mice. These experiments aimed to identify the differences between mice with a modified FSIP2 gene and their counterparts with a normal variant of the gene. The first group of mice had a modified FSIP2 gene created using modern CRISPR-Cas9 genome editing technology, while the second group had a normal variant of this gene. Various parameters, including sperm count, motility, and structural characteristics, were taken into account during the studies.

Key Findings

The study revealed infertility in the first group of mice. The number of viable sperm in the semen of male mice in the first group was significantly lower than normal. Furthermore, more than half of the spermatozoa could not move in a straight line due to defects in the flagellum, although it was mobile. This indicates that structural defects in the flagellum prevent spermatozoa from orienting normally, which is essential for successful conception.

Interestingly, the experiment also showed that mice with higher expression of the FSIP2 gene had longer sperm flagella. This allows reproductive cells to move faster and more efficiently, which likely contributes to increasing the chances of fertilization. These results could be used to develop treatments for male infertility, for example, by stimulating the expression of the FSIP2 gene or correcting its defects through gene therapy.

Practical Importance of the Discovery

The results of the study were published in the scientific journal Development in October 2023. The researchers emphasized that their discovery could open new horizons in the field of male sterility treatment. It not only allows for more accurate diagnosis of sperm motility issues but also helps in developing individualized therapeutic approaches.

The application of the new knowledge may include the use of pharmacological agents that stimulate the correct formation of the fibrous sheath of the spermatozoon's flagellum. The development of genome editing technologies to eliminate mutations of the FSIP2 gene in patients diagnosed with infertility could also be possible. Furthermore, this discovery highlights the importance of early detection of these mutations, which can prevent further fertility issues.

Applications in IVF Programs

Besides natural conception, these techniques may be useful for improving the efficiency of IVF programs (in vitro fertilization), including variants of IVF with sperm donation. These technologies offer new options to couples facing conception difficulties due to structural anomalies in their spermatozoa. By introducing new approaches, the quality of sperm used in IVF programs can be significantly improved, thereby increasing the chances of successful conception.

Research Perspectives

In the future, scientists plan to continue studying the role of the FSIP2 gene in human reproductive function. This will particularly involve analyzing the interactions between FSIP2 and other genes that may be involved in the sperm formation process. At the same time, researchers are working on developing new diagnostic tests that allow for rapid and accurate detection of FSIP2 gene mutations in patients.

Moreover, future developments could include clinical trials of drugs aimed at correcting sperm defects. This will be an important step towards personalized medicine in the treatment of male infertility. Advances in this area will open doors for many patients, giving them the opportunity to realize their dream of becoming parents.