NEW YORK (GenomeWeb) – A large genome-wide association study of male pattern baldness is fleshing out the collection of common variants linked to the trait, pointing to a potential avenue for future polygenic prediction tests.
Researchers from the UK searched for common variants involved in baldness based on array-based genotyping information for more than 52,000 UK Biobank participants between the ages of 40 and 69 years old. Their findings, appearing online yesterday in PLOS Genetics, uncovered hundreds of variants on the autosomal chromosomes or X sex chromosome coinciding with male pattern baldness.
With these data, the team took a crack at coming up with a variant-based tool for predicting baldness in a subset of the original participants. The approach appeared promising for predicting male pattern baldness in the population as a whole, though it has a way to go for making accurate baldness predictions for any given individual.
"We are still a long way from making an accurate prediction for an individual's hair loss pattern. However, these results take us one step closer," senior author Riccardo Marioni, a genomic and experimental medicine researcher at the University of Edinburgh, said in a statement. "The findings pave the way for an improved understanding of the genetic causes of hair loss."
Past genetic studies suggest that some of the strongest genetic contributors to male pattern baldness fall on the X chromosome, the sex chromosome a man inherits from his mom, Marioni and his co-authors noted. Even so, much of the genetic architecture of baldness remains unknown, making it difficult to come up with strategies to predict, treat, or understand the trait or its apparent ties to conditions such as prostate cancer and heart disease.
For their new GWAS, the researchers scoured genotyping data for 16,724 men without hair loss, 12,135 individuals with mild hair loss, 14,234 individuals with moderate hair loss, and 9,781 men with severe hair loss, based on self-reported hair patterns for the Caucasian participants.
The team's analysis led to 247 autosomal variants and 40 X chromosome variants with apparent ties to baldness. A gene-based look at the variants that were over-represented in men with thinning mops highlighted 112 genes on autosomal chromosomes and more than a dozen X chromosome genes.
By repeating their analyses on a subset of 40,000 men, the researchers narrowed in on potential polygenic risk scores for predicting slight, moderate, or severe hair loss in the other 12,874 study participants with between 64 percent and 74 percent sensitivity and 53 percent to 69 percent specificity. They noted that the accuracy of such predictions got a bit of a boost by adding in individuals' age.
More broadly, the study's authors noted that "a substantial proportion of individual differences in hair loss patterns can be explained by common genetic variants on the autosomes as well as on the X chromosome. However, the variance explained by X chromosome variants is much lower for late-onset compared to early-onset male pattern baldness."