If both mammals and medaka have a Y chromosome, the body becomes a male.However, Nagoya University et al. Found in an experiment using a medaka that germ cells have a function of wanting to make the body a female, regardless of whether the body has a Y chromosome.
Germ cells are the source of sperm and eggs and have the ability to be both sperm and eggs.In medaka, when the number of germ cells increases abnormally, the body becomes a female even if it has a Y chromosome and the gene that determines the male works.Furthermore, when the characteristics of germ cells were examined, it was found that germ cells have the ability to make the body a female even before deciding whether to become a sperm or an egg.
For example, in female medaka, when germ cells disrupt the genetic function that determines "whether they become sperm or eggs," the germ cells begin to produce sperm instead of eggs.However, despite this, the body becomes a female.This indicates that germ cells, whether eggs or sperm, retain the ability to femaleize the body.
Comparing the process of ovary formation in females and the process of testis formation in males, the number of germ cells increases and begins to produce eggs in females immediately after the formation of ovaries, whereas in males it produces sperm. It is said that the increase of germ cells stops before.Focusing on the characteristic of "female body" of germ cells revealed in this study, increasing the number of germ cells in females promotes femaleization of the body, and males complete maleization of the body. Until then, it is thought that the growth of germ cells is suppressed to prevent them from becoming females.
By understanding the characteristics of cells that want to make the body a female, it is expected that the understanding of the mechanism that determines the sex of the body will be further deepened in the future.
Paper information:[PLoS Genetics] Germ cells in the teleost fish medaka have an inherent feminizing effect
