The study shows significant variations in gene activity within the mitochondria of males compared to females. It is the first study to investigate the effects of all 37 genes in the mitochondrial genome, which are shared by copepods and humans. The research indicates that males exhibit higher activity across all protein-coding mitochondrial genes than females. Even though the study focuses on small marine creatures known as copepods, the findings have important implications for human health.
According to marine and environmental biologist Suzanne Edmands, “We discovered a significant ‘men are from Mars, women are from Venus’ pattern.”
Edmands is pointing out differences in mitochondria, which are responsible for producing energy, not differences in human psychology.
As a professor of biological sciences at USC Dornsife College of Letter, Arts and Sciences, Edmands recently published her research in the Proceedings of the National Academy of Sciences, highlighting substantial variances in gene activity within the mitochondria of males and females.
Even though the study focuses on copepods, Edmands emphasizes that the findings can significantly impact human medicine. She mentions, “The mitochondrial genome of these animals is very similar to ours, with the same genes, functions, and genome size.”
A plethora of human diseases are associated with dysfunctional mitochondria, affecting various parts of the body including muscles, organs like the liver and pancreas, the brain, and sensory organs like the eyes and ears. Conditions such as muscular dystrophy, diabetes, and Alzheimer’s disease are examples of diseases linked to malfunctioning mitochondria.
While current treatments for these diseases are mostly the same for both men and women, Edmands believes her study indicates that this approach is often inadequate. She states, “Our findings underscore the importance of developing gender-specific mitochondrial therapies.”
Mitochondrial Differences between Genders
Scientists believe mitochondria originated from a single-cell organism that was engulfed by another cell roughly 1.5 billion years ago. Over time, these engulfed organisms specialized in energy production for their host cells. This beneficial symbiotic relationship has endured through evolution.
This ancient amalgamation of two organisms explains why mitochondria have their own distinct genome separate from the cell’s nucleus.
It is already known that gene activity within mitochondria differs between genders. Edmands explains, “Mitochondrial function can vary between men and women, who generally have different energy needs and trade-offs.”
Edmands aimed to delve deeper into these gender differences. Her study sought to identify the most active mitochondrial genes in males and females, as well as how these genes interact with nuclear genes in both sexes.
To ensure that the observed gender differences were due to mitochondria, she studied a copepod species that lacks sex chromosomes.
Sex chromosomes can also cause discrepancies between males and females, and separating these effects from gender-specific mitochondrial effects is challenging.
Study Reveals Significant Gender Variations in Mitochondria
Edmands’ team is the first to examine the effects of all 37 genes in the mitochondrial genome shared by copepods and humans.
She discovered that males display higher activity across all protein-coding mitochondrial genes compared to females. Males also show increased expression of nuclear and mitochondrial genes that interact to impact cellular energy metabolism.
Conversely, females exhibit higher expression of genes linked to the production and maintenance of mitochondria.
Why are these disparities crucial? Despite mitochondria containing only a small portion of the DNA found in the nucleus, the study demonstrated that mitochondrial genes influence processes across all 12 chromosomes within the nucleus, exerting a broad impact.
Furthermore, the mitochondrial and nuclear genes that interacted were primarily distinct between genders.
Implications for Mitochondrial Diseases
Edmands suggests that these findings can guide the treatment of mitochondrial diseases in humans, particularly mitochondrial replacement therapy. This method involves replacing defective mitochondria in a mother’s egg with healthy mitochondria from a donor.
She explains, “Our results indicate that switching to a different type of mitochondria is not as simple as changing a battery. Mismatches between the donor mitochondria and the nuclear DNA can have gender-specific repercussions throughout the genome.”
Understanding the interactions between nuclear and mitochondrial genes, as well as the differences in these interactions between genders, could help healthcare providers select the appropriate type of mitochondria to enhance the success of these therapies.
Future Work on Mitochondria
In upcoming studies, Edmands aims to use additional methodologies to explore gender-specific differences in mitochondrial function. She believes that her research design, which avoids sex chromosomes, may also encourage other scientists to undertake similar studies.
She mentions, “I expect scientists to view this as a convincing demonstration of gender-specific mitochondrial effects on gene expression since it is not confounded by sex chromosome effects.”
