These mice, which exhibit the full range of baldness as seen in human alopecia, are helping researchers uncover the genes involved in the disease.
Genetic basis of alopecia investigated
A recent study by VUMC dermatologist Lloyd E. King Jr., M.D., Ph.D., and colleagues focuses on the genetic foundations of alopecia areata (AA), an autoimmune skin disease that causes patchy hair loss.
The study, published in the August issue of the Journal of Investigative Dermatology, provides evidence that pieces of chromosomes 8 and 15 in mice may harbor genes involved in this disorder.
Although the study doesn’t identify particular genes involved in AA, it does narrow the focus to a few select regions of the genome. This provides researchers a “treasure map” to follow in their search for individual genes that could serve as targets for therapy.
“This article is shorthand for ‘look on this chromosome’ for potential genetic defects,” King said.
Alopecia areata is much more than grandpa’s baldness.
Unlike male pattern baldness, which occurs gradually and in a predictable pattern on the scalp, hair loss in AA can occur suddenly, beginning as small patches on the scalp. The hair loss can progress to total loss of all bodily hair (even eyelashes and eyebrows). It can happen to males or females and can strike at any age.
In AA, the body’s immune system attacks the hair follicles, causing hair to fall out in patches. The disorder affects nearly 2 percent of the total population, including more than 4.7 million people in the United States alone.
There is no cure, and the cause of AA is unknown. However, one in five patients with AA have a relative with the disease, indicating that heredity plays an important role.
In 1990, King and his collaborator on the study, John Sundberg, Ph.D., at The Jackson Laboratory in Bar Harbor, Maine, and adjunct associate professor of Medicine (Dermatology) at VUMC, discovered a mouse strain that spontaneously develops an AA-like condition. These mice exhibited spontaneous, patchy hair loss, and their hair follicles were surrounded by swarms of white blood cells, indicating that the immune system was attacking the follicles. This discovery offered researchers a powerful genetic tool to aid the search for AA-associated genes.
In the current study, King, Sundberg and colleagues analyzed DNA from these AA mice and normal mice. Using a genome-wide screening technique, the researchers identified two areas — on chromosomes 8 and 15 — that were strongly linked to the disease.
These regions contain several promising candidate genes, including those that regulate the immune response, cell death, pigment migration and skin integrity.
Previously, the researchers had found that areas on mouse chromosomes 9 and 17 were also linked to AA. Many of the genes in those regions coded for components of the immune system, including the mouse versions of human leukocyte antigens (HLA) — proteins that coat the surface of nearly all bodily cells and determine your immune uniqueness.
“The areas of linkage in the mouse studies contain the same HLA sites on chromosomes as in humans,” King said. This is important, he adds, because it tells investigators where to look for defective genes in humans.
Building Support
However, performing genetic linkage studies in humans requires a large pool of subjects. To aid in this effort, the National Institute of Arthritis and Musculoskeletal and Skin Diseases and the National Alopecia Areata Foundation (NAAF) have established a national registry to collect genetic and medical information from AA patients and their families.
Families with more than one generation of affected members will be especially helpful in identifying genes involved in AA. King hopes to aid in this effort by recruiting patients for the registry through the Nashville Alopecia Areata Support Group.
“The support groups will help drive the human studies,” King said. By identifying human genes, researchers will then have potential targets for treating AA.
The local NAAF support group meetings, which will be held several times per year, will be hosted by King and third-year medical student Adriana Schmidt. The first meeting will take place on Oct. 13 (see below for additional information).
The meetings will serve as a forum where participants can share information about AA research, discuss practical issues related to treatment and insurance coverage, and support other AA patients and their families in coping with this psychologically devastating condition.
“It’s very helpful in life to see other people in the same boat and find out it’s not what’s on your head, it’s what’s in your head,” King said.
Co-authors on the article include John Sundberg, Kathleen Silva, Renhua Li, and Gregory Cox of The Jackson Laboratory in Bar Harbor, Maine.
This research was supported by grants from the National Alopecia Areata Foundation and the National Institutes of Health.
The Fall meeting of the Nashville Alopecia Areata Support Group will be held Wednesday, Oct. 13 at 1900 Patterson Street, suite 104. An informal gathering will be at 6:30 p.m. and meeting begins at 7 p.m. Topics will include:
• Update on NAAF newsletter events
• Discussion of Nashville support group activities for the year
• Q&A with Lloyd King Jr., M.D., Ph.D.
For additional information about the Nashville AA support group, contact Adriana Schmidt at alopeciatn@yahoo.com.
To enroll in the National Alopecia Areata Registry, visit:
http://www.mdanderson.org/departments/alopecia/ or call the registry Toll Free Number: (866) 837-1050.