It begins with receding hairlines, the forehead becomes higher, the hair at the back of the man's head gets thinner and thinner. Every second man suffers from greater or lesser hair loss. There are hardly any successful counter-measures – despite an enormous range of obscure lotions and tinctures.
It has long been suspected that hereditary factors are important in causing hair loss. However, up to now it was unclear which genes are involved. The researchers in the team headed by Professor Markus Nöthen of the Life & Brain Centre of the Bonn University Clinic and Dr. Roland Kruse of the Skin Clinic of Düsseldorf University Clinic seem to have now discovered one of the factors responsible for the first time.
For several years the researchers had searched nationwide for families in which several men were affected by hair loss. In blood samples taken from the volunteers they then looked for candidate genes – and eventually discovered them: in their initial step they succeeded in narrowing down the search to a series of areas on various chromosomes. In an area where the largest contribution was suspected lay the gene for the androgen receptor. "One variant of this gene was found among men who suffered from premature balding at a very early stage very much more often than among men who still had a full head of hair when over 60," Professor Nöthen says.
More androgen receptors in the scalp
Probably the genetic variant results in more androgen receptors in the scalp. "Our findings permit two explanations," Axel Hillmer from Prof. Nöthen's team explains. "Either more androgen receptors are formed among the men affected, or the variant of the receptor which develops as a result of the genetic change is more stable and is not broken down so quickly. Both mechanisms can lead to the effect of the androgens becoming greater, which in turn brings about hair loss."
The findings are also interesting for the aspect of how hair loss is inherited. The gene for the androgen receptor lies on the x chromosome. Men always inherit the x chromosome from their mother. In many cases men therefore take after their grandfather on their mother's side rather than their father. However, this defect is not simply caused by one gene: "We have indications that other genes are involved which are independent of the parents' sex," Prof. Nöthen stresses. The hereditary defect can therefore sometimes also be passed on directly from father to son. Bald men wanted
In order to identify more genes involved the research team is searching for more volunteers. "Men under 40 with severe hair loss can take part," Dr. Kruse says. "If they have a brother who is affected and the parents are also prepared to give blood samples, so much the better. Volunteers taking part in the study will, of course, be paid for their assistance."
The project is being supported by the German Research Association (DFG) and the Alfried Krupp von Bohlen und Halbach Foundation. Professor Nöthen holds the Alfried Krupp von Bohlen und Halbach Chair of Genetic Medicine. The Life & Brain Centre is a new research team at the Bonn University Clinic which uses state of the art technologies to carry out application-oriented aetiology.
The original paper can be downloaded from the following URL: http://www.journals.uchicago.edu/AJHG/journal/issues/v77n1/42360/42360.web.pdf
American Journal of Human Genetics