Inherent feminizing effect of germ cells: New insights into sex determination

March 29, 2018

Nagoya University-led study shows for the first time germ cells have an inherent property to feminize the body in teleost fish, medaka

Nagoya, Japan - The gender of living organisms is determined either by genetic factors and/or by environmental factors. Interestingly, however, a team of researchers led by Nagoya University previously found that the occurrence of more germ cells -- biological cells capable of uniting with one from the opposite sex to form a new individual -- in female medaka (teleost fish) gonads is essential for female differentiation of gonads. When germ cells are removed in medaka, XX (female) fish show female-to-male sex reversal, while XY (male) fish with excessive germ cells, which is usually associated with egg production, exhibit male-to-female sex reversal.

"This finding implies that, in addition to the most well- known role of germ cells developing into eggs or sperm and produce the next generation, germ cells have a unique and surprising potential to change their surrounding environment," says Toshiya Nishimura, first author of the current study. "However, the molecular basis of, and the stage of gametogenesis critical for, feminization remain unknown."

This question set the researchers to delve deeper into the topic. In their latest study, they generated three different medaka mutants to demonstrate that the feminizing effect of germ cells is not a result of the progression of gametogenesis or a sexual fate decision of germ cells. They found the different stages of germ cells in XX mutants have an ability to feminize the gonads, resulting in the formation of gonads with ovarian structures. In addition to normal ovarian development, the increased number of gonocytes (fetal and neonatal germ cells) is sufficient for male-to-female sex reversal in XY medaka.

What these results mean is that the mechanism underlying the feminizing effect of germ cells is activated before the sexual fate decision of germ cells and meiosis, probably by the time of gonocyte formation in medaka. The study was published in PLOS Genetics.

"Our analyses using medaka collectively also suggest that germ cells acquire the feminizing effect before committing to gametogenesis, while male germ cells undergo a quiescent state before the initiation of spermatogenesis," corresponding author Minoru Tanaka says. "Why do male germ cells need to be quiescent? One possible answer for the biological meaning of the quiescent state of male germ cells may be to prevent the gonad from being feminized until masculinization of somatic cells is established."
-end-
The article, "Germ cells in the teleost fish medaka have an inherent feminizing effect", was published in PLOS Genetics at DOI: 10.1371/journal.pgen.1007259.

Nagoya University

Related Sperm Articles from Brightsurf:

Nut consumption causes changes in sperm DNA function
Researchers have evaluated for the first time the effect of a short/middle-term consumption of a mixture of tree nuts (almonds, hazelnuts and walnuts) on sperm DNA methylation patterns in healthy individuals reporting eating a Western-style diet.

Collecting sperm from Covid-19 patients
How does Covid-19 affect sperm and thus the next generation┬┤s immune system?

Paleontology -- The oldest known sperm cells
An international team of paleontologists has discovered giant sperm cells in a 100-million year-old female ostracod preserved in a sample of amber.

Research captures how human sperm swim in 3D
Using state-of-the-art 3D microscopy and mathematics, Dr Hermes Gadêlha from the University of Bristol, Dr Gabriel Corkidi and Dr Alberto Darszon from the Universidad Nacional Autonoma de Mexico, have reconstructed the movement of the sperm tail in 3D with high-precision.

Overweight and obesity are associated with a low sperm quality
Researchers from the Rovira i Virgili University in collaboration with researchers from the University of Utah have carried out a systematic review and meta-analysis evaluating the association between adiposity (normal weight, overweight, obesity, and low weight) and the sperm quality.

Diet has rapid effects on sperm quality
Sperm are influenced by diet, and the effects arise rapidly.

Sperm may offer the uterus a 'secret handshake'
Why does it take 200 million sperm to fertilize a single egg?

Long duration of sperm freezing makes no difference to live birth rates in large sperm bank study
Despite a time limit imposed in many countries on the freeze-storage of sperm, a new study from China has found that the long-term cryopreservation of semen in a sperm bank does not affect future clinical outcomes.

An important function of non-nucleated sperm
Some animals form characteristic infertile spermatozoa called parasperm, which differ in size and shape compared to fertile sperm produced by single males.

DNA of sperm taken from testicles of infertile men 'as good as sperm from fertile men'
Scientists have found that sperm DNA from the testicles of many infertile men is as good as that of ejaculated sperm of fertile men.

Read More: Sperm News and Sperm Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.
Can't connect to localhost. Errorcode: 1203