Plate Nº 68 · recorded October 10, 2026
Health & Medicine ResearchReported finding
X and Y Chromosomes Shape Disease Risk Far Beyond Sex Determination
A January 2026 Science review by Theodorescu and Dubal argues that X and Y chromosomes shape cancer, brain aging, immunity and heart disease well beyond their role in determining biological sex.
By Nathan Brooks3 min read617 words
In brief
- Review published in Science in January 2026 (DOI: 10.1126/science.aeh0145).
- Co-led by Dr. Dan Theodorescu (University of Arizona Cancer Center) and Dr. Dena B. Dubal (UCSF).
- Roughly 15% of genes on the silenced X chromosome escape inactivation, giving female cells extra gene doses.
- In men, loss of the Y chromosome has been linked to cancers, heart disease, severe infections and Alzheimer's.
- Mice relying mostly on the mother's X showed faster brain aging and memory decline.
A review published January 2026 in Science pulls together evidence that the X and Y chromosomes do far more than set biological sex — they help govern how cells age, how the immune system responds, and how diseases from cancer to Alzheimer's develop. The authors argue that this hidden genetic layer could change how doctors diagnose, treat and design clinical trials.
What did the review actually find?
The review was co-led by Dr. Dan Theodorescu, director of the University of Arizona Cancer Center, and Dr. Dena B. Dubal of the University of California, San Francisco. It synthesizes existing evidence from human studies, mouse models and genomic technologies into a single framework covering five health areas: aging, cancer, neurological disease, immune function and cardiometabolic conditions.
"X and Y chromosomes are often thought of as simple determinants for biological sex, but their role in human health is much larger," Theodorescu, the Nancy C. and Craig M. Berge Chair, said. "Our review shows that these chromosomes carry genetic instructions that shape how our cells age and how our bodies defend against major diseases throughout our lives."
How can one extra X chromosome affect aging?
Women have two X chromosomes, but early in development, one is largely switched off in each cell. Roughly 15% of its genes escape this silencing, and others can reactivate with age, giving female cells extra doses of certain gene products. Each cell also keeps either the mother's or the father's copy active, a choice that has measurable consequences.
In mice, cells that relied mostly on the mother's X showed faster brain aging and steeper memory decline. The same parental-origin effect may operate in humans, though direct evidence is thinner.
Why does losing a chromosome matter?
With age, some cells quietly lose a sex chromosome. In women, X loss is linked to higher leukemia risk, though broader effects are not yet mapped. In men, Y chromosome loss — most often measured in blood — has been tied to cancers, heart disease, severe infections and Alzheimer's disease.
"When we look inside human cells, we see that X and Y chromosomes are participants in health and disease throughout a person's life," Theodorescu said. He added that tumors losing the Y chromosome can evade the immune system yet sometimes respond better to immunotherapy — a paradox his own lab first described.
What could change in medicine?
The review grew out of the 2025 National Institute on Aging Workshop on sex differences across the lifespan, run with Francesca Duncan of Northwestern University's Feinberg School of Medicine. Its practical pitch is straightforward: if sex chromosomes shape disease risk independent of hormones, then diagnosis and treatment should account for them.
The authors outline several implications:
- Trial design. Studies should record participants' chromosomal profiles, not just sex assigned at birth.
- Cancer screening. Y chromosome loss in blood could serve as an early warning biomarker.
- Drug response. Tumors with Y loss may behave differently on immunotherapies than tumors without it.
- Neurological care. Parental origin of the active X may modify brain aging trajectories.
What remains unknown?
The review stresses that much of the evidence comes from mouse models or correlational human data. Whether Y loss actively drives disease or merely marks it is still debated. The functional impact of X reactivation with age, and which tissues it matters most in, also need direct testing.
Co-authors include Fabrisia Ambrosio of the Schoen Adams Research Institute at Harvard Medical School and Michael B. Stout of the Oklahoma Medical Research Foundation. The work, published as DOI 10.1126/science.aeh0145, is part of a broader push to make precision medicine sex-aware from the first blood draw to the last clinical visit.
via Medical Xpress (Source)