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The Cutting Edge

Father’s X Chromosome May Yield Clues to Higher Rates of Autoimmune Disease in Women

DNA methylation depicted

Increased DNA methylation when the X chromosome is of paternal origin compared to when it is of maternal origin. DNA methylation depicted in yellow. Image: Courtesy of Dr. Lisa Golden

UCLA scientists have discovered one reason why autoimmune diseases are more prevalent in women than in men. While males inherit their mother’s X chromosome and father’s Y chromosome, females inherit X chromosomes from both parents. New research, which shows differences in how each of those X chromosomes is regulated, suggests that the X chromosome that females get from their father may help to explain their more active immune system.

It’s been known for many years that women are more susceptible to autoimmune diseases than men are,” says Rhonda Voskuhl, MD, Jack H. Skirball Chair in Multiple Sclerosis Research and director of the UCLA Multiple Sclerosis Program. “Figuring out why can help us develop new drugs to treat these autoimmune diseases.”

Rhonda R. Voskuhl, MD

Rhonda R. Voskuhl, MD

Autoimmune diseases, such as multiple sclerosis and rheumatoid arthritis, are conditions that affect the body’s ability to fight viruses, bacteria and infections. The problem causes a person’s immune cells to attack the body instead. Women generally have stronger immune responses than men, with more robust responses to some vaccinations and infections. However, this heightened immune system also makes women three times more likely than men to develop multiple sclerosis and nine times more likely to develop lupus and more prone to a host of other autoimmune diseases, Dr. Voskuhl says. The effect of sex hormones — testosterone and estrogen — in these differences has been well-studied, but the role of sex chromosomes has been less clear.

Dr. Voskuhl and her colleagues focused on differences between the X chromosomes inherited from each parent. They first analyzed expression levels of genes in mice with the male (XY) and female (XX) chromosome set. They identified a handful of immune-system-related genes on the X chromosome that are expressed less — producing fewer corresponding molecules — in the immune cells of female mice.

To further study these differences, Dr. Voskuhl’s team next compared mice that had just one X chromosome — either a maternal or paternal X chromosome. They determined levels of methylation — the addition of methyl chemical groups to DNA — in the X chromosomes. Methylation is known to turn down, or block, the expression of genes. And while the methyl groups aren’t part of the DNA sequence itself, patterns of methylation can be passed from parent to child. The researchers discovered that there was more methylation on paternal than on maternal X chromosomes. Finally, they confirmed that several genes on the X chromosome were expressed less when the X chromosome was of paternal as compared to maternal origin.

“What we’re talking about here is not mutations that affect gene sequences, but instead signals that affect how the same sequence of genes is differentially expressed in females versus males. These differences would be missed in traditional genetic studies,” Dr. Voskuhl says.

The findings suggest that the X chromosomes packaged into sperm and passed from father to daughter may have higher levels of methylation than the X chromosomes passed along in eggs from a mother to her offspring. This methylation dampens the expression of some immune system genes in females, making their immune activity different from males.

“If you can find regulators of methylation that target these differences, you might be able to reduce the immune responses of females to treat autoimmune diseases,” Dr. Voskuhl says. “Going forward, when one considers sex as a biologic variable in diseases, it can lead to new treatment strategies.”

— Sarah C.P. Williams

 

“The X-linked Histone Demethylase Kdm6a in CD4+ T Lymphocytes Modulates Autoimmunity,” The Journal of Clinical Investigation, August 12, 2019


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Winter 2020

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IN THIS ISSUE
  • Lessons from Sherm
  • Father’s X Chromosome May Yield Clues to Higher Rates of Autoimmune Disease in Women
  • Researchers Create Accurate Model of Organ Scarring
  • Biomarker Predicts Which Heart-failure Patients at Higher Risk of Death within One-to-three Years
  • Targeted Therapy Drug Extends Lives of Women with Aggressive Breast Cancer
  • Can a “Battery Leak” Trigger the Onset of Type 2 Diabetes?
  • Molecular Changes in Cells of Eye’s Lens Predict Future Cataracts
  • UCLA Addresses Increasing Demand with New Master’s in Genetic Counseling
  • Truth Seeker
  • Sherm
  • Repairing and Reversing Damage Caused by Huntington’s Disease
  • Cells’ Mitochondria Work Much Like Tesla Battery Packs
  • The Who and Friends Rock Private Show for UCLA Health and Teen Cancer America
  • A Confounding Case
  • Body Image Concerns Are Universal
  • “We Do Better with Diversity”
  • Annual UCLA Health System Board Meeting Turns Its Focus to Cardiac Care
  • UCLA Operation Mend Cheered on at New York City Veterans Day Parade
  • A Decade in Review: 7 Exciting Health Care Breakthroughs
  • MRI May Help Doctors Differentiate Causes of Memory Loss
  • On the Road to Health Care Equality
  • Learning To Listen
  • Photo Synthesis
  • Awards & Honors
  • In Memoriam
  • David Geffen Adds $46 Million to Landmark Medical Scholarships Program
  • Nearly 2,000 Guests Attend Party on the Pier for UCLA Mattel Children’s Hospital
  • Golden Visionary Ball Raises More than $1 Million for UCLA Neurosurgery
  • Dr. Hans Gritsch Named Inaugural Chair in Kidney Transplantation
  • Nonprofit Heart of the Brain Fuels the Fight against Brain Cancer
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