Tuesday, May 28, 2024
HomeWellnessHair LossSNP, SNP, SNP! Where's Your Hair?

SNP, SNP, SNP! Where’s Your Hair?

Will I go bald? Forecasting male pattern baldness through DNA testing.

A team led by Dutch scientists have developed a genetic tool for predicting male pattern baldness with a superior edge. 1  

Hair is a powerful symbol of male youth, vigour and vitality in many cultures. Think Samson and Delila, Poseidon’s magical hair or Navajo traditions. The part hair played in status and ritual, and why certain hairstyles predominated is a fascinating aspect of archaeology. Right now, wigs and paintings help historians to make educated guesses, but what if there was a way to look deep into the past?

Male pattern baldness isn’t just a historical concern. For many chaps, male pattern baldness feels like the end of their youthful looks, signaling transition into middle age. By the time they accept that their hair is thinning it can be too late for an effective haircare routine. Would you find it useful to know whether to make an appointment with a trichologist early on? 

Put away your crystal ball; it’s all in the genes.

DNA Testing for Male Pattern Baldness

University of Rotterdam researchers have developed a genetic test that can foretell whether you will lose your hair. With an accuracy of 69–71% for hair loss, this test is the most successful predictive tool yet. 

The DNA test can also forecast how much hair you will lose. The test predicted severe baldness with an accuracy of approximately 72%, moderate baldness to 63%, slight baldness with 60% precision and no hair loss with an accuracy of 70%. 

A cut above the rest

Androgenetic alopecia is a progressive form of hair loss. It is the most common type of male pattern baldness, experienced by 80% of men with European ancestry. In brief, for men who have it, the effects of sex hormones make head hair follicles shrink. Once you hit puberty, sex hormones (or androgens) trigger the follicles to devote less time to the growth phase of making a hair. This means that as time goes on, the hairs get increasingly short and fine. Eventually, the follicles can no longer produce a hair. If your hair is fine or has a short growth phase to begin with, it can accelerate the effects on your follicle.2 

So what makes a hair follicle vulnerable to sex hormones or other factors? The answer is in your DNA. Ever notice how a set of brothers might look increasingly similar as they age? A lot of that family resemblance can be put down to their hair line.3  

It’s long been known that a large component of male pattern baldness is inherited. While a complex mix of genes inherited from both parents can influence hair loss, most comes from genes carried on the X chromosome.3,4,8 That’s the chromosome you inherit from your mother. A 2017 study performed by University of Bonn geneticists found that 63 genetic markers are inherited along with male pattern baldness.5 These genes can explain up to 39% of the variation in how hair looks between individuals. This and a few similar studies, inspired a team led by Manfred Kaiser, University of Rotterdam, to develop a predictive model for hair loss. The Rotterdam researchers combed through genetic data from nearly 200,000 men to tease out the test published in the scientific journal, Nature, in 2022.1 

Making a Model

In the past, efforts to make an accurate test for male pattern baldness failed. Because so many genes are involved in the inheritance of hair loss, researchers need an absolutely enormous number of men to donate DNA samples. The more complicated the inheritance pattern, the more genes you need to identify. The more genes involved, the bigger the pool you need to sample to pick up all the different combinations. Earlier models were held back by small sample sizes.6 Fortunately, Kaiser and his team had access to an enormous DNA database—the UK biobank.7

Designing the model was complex work. Firstly, the researchers combined the results of several published studies to identify genetic markers that are inherited along with male pattern baldness. A genetic marker is a specific sequence of DNA with a known location on a chromosome, for example, a single nucleotide polymorphism (SNP). An SNP is a sort of “error” that occurs at a single site in your DNA sequence. Most SNPs are harmless and account for the natural variation within the population. They carefully chose 117 SNPs markers. They based selection on a marker’s association with androgenetic alopecia and whether they were in or near genes that have something to do with hair. 1

Snipping the SNPs

Next, they figured out how much influence each individual SNP had on whether a man would lose his hair. They searched through 187,435 men in the UK biobank to find out how often each SNP turned up along with male pattern baldness. This allowed them to assign a “likely to cause baldness” risk factor to each genetic marker or combination of markers. They added together all the different probability profiles for the 117 SNPs to make an overall model. Next, they tested the model to see if it worked. They fed in DNA sequences from a new set of samples, and calculated a baldness “risk factor” for each man. That is, depending on what combination of SNPs the man had, they could give the odds of whether he would be bald.

Finally, they looked at the anonymized user profiles of the DNA donors to see how often their model got it right. It was pretty successful managing an accuracy of 69–71% for a hair loss/no hair loss result. Overall, the genetic test can predict severe baldness with a prediction accuracy of approximately 72%. Moderate baldness with an exactness of 63% and slight baldness were predicted with a precision of 60%. 
 

X Factor

Interestingly, the scientists found that the most predictive SNP for male pattern baldness was rs12558842 on the X chromosome. This variant, located near the androgen receptor gene, could predict the likelihood of hair loss vs. no hair loss with an accuracy of 60.8%.1 This confirmed the theory that male pattern baldness is inherited largely via our mother on the X chromosome.4 In other words, it might be worth paying a little extra attention to your maternal grandfather’s hairline next time you visit.

Exactly, where and when you can expect to lose your locks remains to be seen. When the scientists factored age into their risk profiles, however, the results became more accurate.

It’s clear male pattern baldness prediction still has a way to go, but with several groups working towards it, we won’t be waiting long. 1

Hair and Health

For some men, the inevitability of hair loss has intense sociopsychological impacts. In fact, studies have drawn links between male pattern baldness and depression, anxiety, even social withdrawal. Given the social value we attach to hair, losing it can hit a man’s confidence hard.9 DNA testing may pave the way towards better strategies for hair loss prevention or even ways to restore lost hair.

Interest in androgenetic alopecia isn’t entirely aesthetic. The genes that make your hair follicles overly sensitive to testosterone are also involved in other physiological processes. Studies have tied it to several health disorders, such as cardiac and metabolic diseases. Scientists have theorized that the androgenetic mutations related to male pattern baldness may also put you at risk of these age-related illnesses. Men who go bald early in life might need to undergo cardiac screening or prostate checks sooner than men who keep their coifs.10,11

Wanted!

Last but not least, while historians might be looking forward to building better reconstructions of characters from ancient history, modern men might want to consider buying a hat. American police have experimented with extrapolating skin colour from crime scene DNA.12 Think twice before putting that hair-brained plan into action. The old bill might be able to make a more accurate wanted poster than you expect.

References 
1 Chen Y, Hysi P, Maj C, et al. Genetic prediction of male pattern baldness based on large independent datasets. European Journal of Human Genetics. 2022;31(3):321–328.

2 Ho CH, Sood T, Zito PM. Androgenetic Alopecia. In: StatPearls. StatPearls Publishing; 2024. Accessed April 17, 2024. http://www.ncbi.nlm.nih.gov/books/NBK430924/

3 Yap CX, Sidorenko J, Wu Y, et al. Dissection of genetic variation and evidence for pleiotropy in male pattern baldness. Nat Commun. 2018;9:5407. doi:10.1038/s41467-018-07862-y

4 Heath AC, Nyholt DR, Gillespie NA, Martin NG. Genetic Basis of Male Pattern Baldness. J Invest Dermatol. 2003;121(6):1561-1564. doi:10.1111/j.1523-1747.2003.12615.x

5 Heilmann-Heimbach S, Herold C, Hochfeld LM, et al. Meta-analysis identifies novel risk loci and yields systematic insights into the biology of male-pattern baldness. Nature Communications. 2017;8(1).


6 Hagenaars SP, Hill WD, Harris SE, et al. Genetic prediction of male pattern baldness. PLOS Genetics. 2017;13(2).

7 Bycroft C, Freeman C, Petkova D, et al. The UK Biobank Resource With Deep Phenotyping and genomic data. Nature. 2018;562(7726):203–209.


8 Liu F, Hamer MA, Heilmann S, et al. Prediction of male-pattern baldness from genotypes. European Journal of Human Genetics. 2015;24(6):895–902.

9 Alfonso M, Richter-Appelt H, Tosti A, Viera MS, García M. The psychosocial impact of hair loss among men: A Multinational European study. Current Medical Research and Opinion. 2005;21(11):1829–1836.

10 Sharma K, Jindal A. Association between androgenetic alopecia and coronary artery disease in young male patients. International Journal of Trichology. 2014;6(1):5.

11 Huang C-K, Lee SO, Chang E, Pang H, Chang C. Androgen receptor (AR) in cardiovascular diseases. Journal of Endocrinology. 2016;229(1).


12 Walsh S, Liu F, Wollstein A, et al. The HIrisPlex system for simultaneous prediction of hair and eye colour from DNA. Forensic Science International: Genetics. 2013;7(1):98–115.

Lauryn Doherty
Lauryn Doherty
Lauryn is a science correspondent for Medical News Bulletin. She graduated from Trinity College Dublin with a Bachelor of Science in Human Health and Disease. Lauryn has expertise in the fields of neuroscience and immunology, which she developed through her work as a research assistant. Her interest in scientific writing blossomed during her final year of university whilst completing her undergraduate thesis on the ‘Neuroinflammatory effects of Birth Asphyxia’. Lauryn has also worked on various medical education projects during her time as an intern. She is particularly passionate about public health and clinical epidemiology and dreams of pursuing a career in medical writing.
RELATED ARTICLES

LEAVE A REPLY

Please enter your comment!
Please enter your name here

Latest News and Articles

SUBSCRIBE TO OUR NEWSLETTERS

Stay Connected
10,288FansLike
820FollowersFollow
249FollowersFollow
2,787FollowersFollow

Article of the month

Recognizing HIE: A Call for Advocacy

Have you heard of HIE? It’s the second leading cause of infant mortality and lifelong disability worldwide. 2-3 per 1,000 live births in high-income...

Joke Of The Day – May 29

Doctor to the patient: You have been diagnosed with a highly contagious disease. We will have to quarantine you and you’ll only be fed cheese and...

ADVERTISE WITH US

error: Content is read-only and copy-protected.