Male pattern baldness linked to Parkinson's disease
Using data from its unique online research platform, 23andMe, a leading personal genetics company, has contributed to the finding of six novel genetic associations for early onset male pattern baldness (androgenetic alopecia) in a genome-wide association study now published online in the journal PLoS Genetics.
"The 23andMe Research Platform is a robust source of new genetic discoveries. Nearly 90 percent of our more than 150,000 customers participate in our online research, " stated 23andMe CEO and co-founder Anne Wojcicki. "23andMe is making discoveries faster and more cost effectively than traditional research models," added Wojcicki.
The study, led by Dr. Brent Richards of McGill University, combined genome-wide association data from seven cohorts, comparing men with "early onset" male pattern baldness with older men who had experienced little or no hair loss. 23andMe customers represented more than half of all the cases in the study. The combined analysis was able to identify six new loci associated with early onset baldness, in addition to replicating two previously known loci. Additional data collected from 23andMe participants showed that a risk score based on genotypes at the eight associated loci was strongly predictive of whether someone would report early onset male pattern baldness or not.
Two of the new loci are in or near histone deacetylase genes HDAC4 and HDAC9. Histone deacetylases regulate expression of other genes by modifying histones, which are proteins responsible for DNA packaging. Both of these genes are thought to have roles in regulation of androgen hormone pathways, which are important in prostate cancer as well as male pattern baldness. "Baldness and prostate cancer risk have been linked in several previous studies," explained 23andMe researcher David Hinds, Ph.D., "and our new findings may help to explain these observations."
"Unexpectedly, the study found that another of the newly associated loci -- in a region of chromosome 17 -- is also associated with Parkinson's disease," added Dr. Hinds. "23andMe was uniquely positioned to further investigate this relationship, thanks to our existing Parkinson's disease community, many of whom have also taken our hair loss survey."
This genomic region is special because it is spanned by a large, common inversion polymorphism -- a long stretch of DNA that is flipped end-to-end in many people. A consequence of this rearrangement is that genes in this region tend to be inherited together, and it is difficult to say whether the shared association is due to variation in a single gene that affects both conditions, or due to variation in two unrelated genes inherited together due to the inversion.
"The study found that even after accounting for this shared association, men were still more likely to report both male pattern baldness and Parkinson's disease than would be expected by chance," continued Dr. Hinds. "This suggests that there may be additional shared genetic or environmental risk factors that predispose towards both conditions," he concluded.
These results continue to validate 23andMe's methodology in combining self-reported data on phenotypes gathered via web-based questionnaires and genotypic data derived from self-collected saliva samples. 23andMe had previously published its first proof-of-concept results in the journal PLoS Genetics in June 2010 which reported novel associations for unusual traits such as asparagus anosmia and photic sneeze reflex and replicated associations for other common genetic traits, and recently published the discovery of two novel genetic associations for Parkinson's disease in PLoS Genetics, and presented a major replication study of over 180 genetic associations in the journal PLoS ONE in August 2011. In April of 2012, 23andMe published a study online in the journal PLoS ONE which reported five novel significant genetic associations for hypothyroidism in the largest known genome-wide association study of hypothyroidism conducted to date.