Research groups at Chubu University, Kinki University, and Kyushu University have elucidated the molecular mechanism of azoospermia using mice.This research is a joint result with Waseda University, Tokyo Institute of Technology, Osaka University, Tokyo University, Osaka City University, and Fuso Pharmaceutical Industry.
Eggs eventually disappear with age, but sperm continue to exist.This is because there are stem cells that are the "source" of sperm in the testis, and they have both functions of cell division (self-renewal) that produces the same stem cells as themselves and cell differentiation that produces sperm.It is said that if an abnormality occurs in the mechanism of these stem cells, sperm cannot be produced and eventually azoospermia occurs.
This time, the mechanism by which sperm stem cells divide but abnormal differentiation occurs, resulting in azoospermia.Interestingly, it was found that this mechanism is regulated by the testis type of a protein that binds to DNA called "histones" that is conserved from yeast to humans.Mice that lost this testicular histone were apparently perfectly normal and healthy, but males became azoospermia and became completely infertile.
Furthermore, structural analysis of this histone protein-DNA complex revealed that its binding was slightly weaker than that of the normal histone-DNA complex present in somatic cells, a special histone found only in this testis. It is speculated that the chemical properties of the sperm stem cells were the cause of the non-formation of sperm.
Further studies are needed to determine whether the molecular mechanism of sperm stem cell function discovered in mice can be applied to humans as it is.In the future, it is expected that the development of this research will lead to the development of diagnostic tools for male infertility and the elucidation of the causes of male infertility.
