Nav: Home

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:

New test assesses sperm function
Two new publications in the journal Molecular Reproduction and Development validate the usefulness of a test that determines if sperm can capacitate, a process that allows them to fertilize an egg.
Mystery of how sperm swim revealed in mathematical formula
Researchers have developed a mathematical formula based on the rhythmic movement of a sperm's head and tail, which significantly reduces the complexities of understanding and predicting how sperm make the difficult journey towards fertilizing an egg.
Sperm changes documented years after chemotherapy
A Washington State University researcher has documented epigenetic changes in the sperm of men who underwent chemotherapy in their teens.
Out of gas and low on sperm?
Sperm are constantly replenished in the adult male body. Understanding the workings of stem cells responsible for this replenishment is expected to shed light on why male fertility diminishes with age, and possibly lead to new treatments for infertility.
Fish sperm race for reproductive success
Many organisms compete for access to and acceptance by mates.
What does the sperm whale say?
When a team of researchers began listening in on seven sperm whales in the waters off the Azores, they discovered that the whales' characteristic tapping sounds serve as a form of individual communication.
Smoking may have negative effects on sperm quality
A recent study found that that sperm of men who smoke has a greater extent of DNA damage than that of non-smokers.
How females store sperm
The science of breeding chickens has revealed part of the mystery of how certain female animals are able to store sperm long-term.
Female birds select sperm 'super swimmers'
Sperm with shorter heads and longer tails are better at fertilising eggs, study reveals.
Why fruit fly sperm are giant
The fruit fly Drosophila bifurca is only a few millimeters in size but produces almost six centimeters long sperm.

Related Sperm Reading:

The Sperm Meets Egg Plan: Getting Pregnant Faster
by Casey Shay Press

The Great Sperm Whale: A Natural History of the Ocean's Most Magnificent and Mysterious Creature
by Richard Ellis (Author)

Sperm Donor Wanted

Sperm Donor = Dad A Single Woman's Story of Creating a Family With an Unknown Donor
by Outskirts Press

The Pea that was Me: A Sperm Donation Story
by Kim Kluger-Bell (Author)

Sperm Whales: Social Evolution in the Ocean
by Hal Whitehead (Author)

It's So Amazing!: A Book about Eggs, Sperm, Birth, Babies, and Families (The Family Library)
by Robie H. Harris (Author), Michael Emberley (Illustrator)

Making Violet: A Sperm Donor Story
by Erin DeVore (Author)

How to Improve Your Sperm Count: Natural Ways to Increase Sperm Count to aid Conception and Boost Fertility (Fertility, infertility, conceive & Get Pregnant Book 1)

Best Science Podcasts 2018

We have hand picked the best science podcasts for 2018. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Hacking The Law
We have a vision of justice as blind, impartial, and fair — but in reality, the law often fails those who need it most. This hour, TED speakers explore radical ways to change the legal system. Guests include lawyer and social justice advocate Robin Steinberg, animal rights lawyer Steven Wise, political activist Brett Hennig, and lawyer and social entrepreneur Vivek Maru.
Now Playing: Science for the People

#495 Earth Science in Space
Some worlds are made of sand. Some are made of water. Some are even made of salt. In science fiction and fantasy, planet can be made of whatever you want. But what does that mean for how the planets themselves work? When in doubt, throw an asteroid at it. This is a live show recorded at the 2018 Dragon Con in Atlanta Georgia. Featuring Travor Valle, Mika McKinnon, David Moscato, Scott Harris, and moderated by our own Bethany Brookshire. Note: The sound isn't as good as we'd hoped but we love the guests and the conversation and we wanted to...