The inaugural gene mapping study on human scalp hair whorls shows not only that hair whorl direction has a genetic basis, but that its expression may be affected by multiple genes. Four variants that could potentially influence this phenomenon were identified and published in the Journal of Investigative Dermatology.
Hair whorls, an easily observed human trait, are circular patches of hair growing out from specific points along hair follicle orientations in a circular fashion. Their numbers (single or double whorl) and directions (clockwise, counterclockwise or diffuse) define them.
As whorl patterns have been observed among patients with abnormal neurological development, understanding their genetic basis may provide key insight into biological processes.
The inaugural genome-wide association study (GWAS) on human scalp hair whorls was performed among 2,149 Chinese individuals from the National Survey of Physical Traits cohort, followed by a replication study in 1,950 individuals from the Taizhou Longitudinal Study cohort.
Dr. Sijia Wang from the Shanghai Institute of Nutrition and Health of the Chinese Academy of Sciences noted: “Understanding why we look the way we do can be difficult. My research group is studying various genes associated with fingerprint patterns, eyebrow thickness, earlobe shape, and hair curliness that we find fascinating.”
“Hair whorl was one of the traits we were interested in studying. Conventional wisdom suggests that its direction is controlled by one gene with Mendelian inheritance, yet our results show otherwise; instead, it appears to be affected by multiple genes acting together for polygenic inheritance.”
The study identified four associated genetic variants at 7p21.3, 5q33.2, 7q33 and 14q32.13 that may influence hair whorl direction by altering cell polarity of hair follicles – possibly also with implications for neural tube closure and growth in the cranium.
Professor Wang commented, “While previous work explored possible correlations between hair whorl patterns and abnormal neurological development, no genetic associations could be detected between hair whorl direction and behavioral, cognitive or neurological phenotypes. While we still lack answers as to why we look the way we do, curiosity will help lead us towards finding solutions.”
