Why Only Mothers Pass Mitochondrial DNA to Their Children

Mitochondria, which produce energy for cellular functions, have their own genome — and we all inherit our mitochondrial DNA (mtDNA) entirely from our mothers. (By convention, the word “genome” refers to nuclear DNA, so the “mt” distinguishes this specific form.) Scientists have recognized this reproductive curiosity for ages, but have not resolved how it happens. The phenomenon is highly conserved, occurring in most species on Earth, and is seemingly crucial for reproduction. Researchers theorize that if maternal and paternal mtDNA both ended up in a fertilized egg, they would compete in ways that are detrimental. However, the precise mechanisms behind the loss of paternal mitochondrial DNA have not been elucidated — until now.

Biochemist Dmitry Temiakov, PhD, and colleagues, used a sensitive method to detect DNA in sperm and showed that mature sperm do not carry any intact mitochondrial DNA. This was a surprise because the germline stem cells that end up growing into mature sperm contain plenty of mitochondrial DNA. So the next question was: When and how do sperm lose that genetic material? Dr. Temiakov’s team looked for clues by exploring molecular pathways involved in sperm maturation. They identified a specific protein called mitochondrial transcription factor A, or TFAM. In most other cells, TFAM serves as a helper molecule for mitochondrial DNA, but during sperm generation, the protein gets modified and becomes unable to gain entry into mitochondria and instead accumulates in the nucleus. Without TFAM, the genetic material in mitochondria is unprotected from degradation, and thus, mature sperm are left without any mtDNA.

“Nature ensures maternal mtDNA inheritance,” Dr. Temiakov says. That means it’s biologically important and that there are likely multiple pathways to prevent the transmission of paternal mtDNA, he says. “We have uncovered one of them.” While the discovery is exciting, he adds that there’s much more to learn. In addition, this and future findings may improve our understanding and treatment of male infertility, especially in cases where sperm parameters are normal.

By Jill Adams

Trans Patients are Patients

Approximately 1 million adults in the United States identify as transgender or nonbinary (TGNB). TGNB people often face significant barriers in accessing health care. Research has shown that part of the problem is a lack of healthcare providers who are familiar with or know how to appropriately care for them. In a recent study, urologist Paul Chung, MD, teamed up with population health researcher Rosie Frasso, PhD, SM, CPH, to find out what genitourinary and sexual symptoms transfeminine individuals experience.

“Part of our goal was trying to educate providers about the genitourinary symptoms that TGNB patients may experience so we can be more aware and therefore provide better care,” says Dr. Chung.

The researchers interviewed transfeminine participants assigned male at birth, all of whom were ages 18 and older. About half of participants had undergone gender-affirming surgery and were on hormone therapy.

The interviews revealed that TGNB people experience many of the same genitourinary and sexual symptoms as cisgender individuals. For example, participants experienced uncontrolled urine leakage, an inability to completely empty the bladder when urinating and painful, burning sensations when urinating as well as low libido, an inability to reach orgasm and erectile dysfunction.

However, not all participants felt comfortable speaking with a provider about these sensitive issues. TGNB patients have unique medical needs, such as side effects from hormone therapy and healing from gender-affirming surgery which may exacerbate or change the experience of the above symptoms.

The research confirmed that participants felt more comfortable when speaking with providers who had expertise and additional training specifically in caring for them. TGNB patients have avoided care due to providers being unfamiliar and unable to communicate effectively with them about their unique needs.

“If we are aware of what their needs may be, then we can ask them proactively and bring up issues that they may be reluctant to talk about,” says Dr. Chung. “At the same time, we don’t want providers to assume that any problem a patient has is always related to being transgender.”

“It’s not always about a patient being trans. A lot of it is just being a patient and having needs,” he says. “Patients are patients.”

By Roni Dengler

Prisons Don’t Offer Women the Menstrual Supplies They Need

Over 800 million people menstruate daily, but menstrual products are often expensive and out of reach to those in poverty; many women will spend thousands of dollars over their lifetime on menstrual products, and new research shows that the price of menstrual pads and tampons has risen nearly 10% due to inflation. While these statistics reveal the struggles that many women, girls, and trans men face to stay comfortable and active during their periods, they can conceal a more severe problem: menstruating people in prison face much worse conditions.

“It’s pretty horrific,” says nursing professor Patricia Kelly, PhD, MPH, APRN. “The environments inside these facilities are awful in general, but when it comes to any kind of privacy or access to supplies, it’s clear there are a lot of injustices and inequities.”

In a recent study published in the Journal of Women’s Health, Dr. Kelly surveyed women who had been incarcerated in Kansas jails and prisons about their access to menstrual supplies, and how that access had impacted their lives. She found that over half of the women received less than five menstrual products at intake, an amount only enough to cover one or two days of menstruation. One third of women said they needed to trade or barter for menstrual products as supplies available for purchase in the commissary were too expensive. Many women said they had to use menstrual products for longer than recommended, or fashion makeshift solutions like toilet paper, rags, or even clothing, risking infection, irritation and life-threatening toxic shock syndrome.

These conditions can threaten more than just physical health. “There’s a risk of loss of humanity when you’re bleeding down your leg, or when you can’t properly attend the few activities that are available to you while incarcerated,” says Dr. Kelly.

She hopes these findings can serve as a jumping-off point to improve menstrual equity — a movement that aims to ensure fair, equal, and affordable access to menstrual products and support for all individuals — in the American criminal legal system.

By Marilyn Perkins