Public interest in male pattern baldness is rooted in cosmetic concern. However, baldness is also worth studying interesting for its interesting combination of biological characteristics: it is strongly hairitable , sex-limited, age-related and common, affecting 80% of Caucasian males. Genetically-speaking, baldness is a complex trait, meaning that there are a multitude of contributing genetic and environmental factors. These characteristics make baldness an attractive trait to study. Why does it only occur in males? Why is baldness so predictably patterned: from scalloped temples and hairline retreat, to thinning crown, to the dreaded end-stage horseshoe ? And how heritable is it? Is your maternal grandfather s dratted X-chromosome really to blame?
We studied the genetics of male pattern baldness genetics in 205,327 European males from the UK Biobank. We found that baldness is strongly genetic up to 62% heritable. Common genetic variants accounted for almost 40% of heritability, meaning that most of the variants that contribute to baldness are widely spread throughout the population. However, the more baldness-associated variants one has, the more likely that they will go bald.
We also found that the genetic variants contributing to baldness are numerous, rather than being from a few rare mutations. 624 independent regions scattered across the genome were robustly associated with increased risk of baldness. We were particularly interested in the X-chromosome as it is often neglected in genetic analyses, yet altered androgen receptor sensitivity is associated with baldness. Of the 624 associated regions, 26 were on the X-chromosome, and these made a disproportionate contribution to the heritability.
We looked for whether baldness shares a genetic basis with other traits. Interestingly, there was consistent correlation between increased baldness severity and earlier puberty onset in both sexes (exhibited by facial hair onset and age of voice breaking in males, age of menarche in females, and reduced growth spurt in both sexes). There were also unexpected genetic correlations with increased bone mineral density and pancreatic beta-cell function. These genetic correlations may plausibly be explained by shared androgen pathways. There were also suggestive correlations with reproductive traits such as fewer number of children fathered in males, and fewer live births and increased age of first birth in females. They collectively imply a weak association between increased baldness severity and reduced reproductive fitness.
Overall, we provide genetic insights into baldness: a trait of interest in its own right, with additional value as a model sex-limited, complex trait.
|12505||Dissecting the genetic basis of relationships between early-life and later-life events|
|Return ID||App ID||Description||Archive Date|
|2904||12505||Dissection of genetic variation and evidence for pleiotropy in male pattern baldness||30 Nov 2020|