There are two forms of human ear wax, wet and dry, determined by one specific gene. Wet ear wax is common in whites and African Americans; dry ear wax is common in Asians and native Americans. Ear wax is produced by the ceruminous apocrine gland (other apocrine glands being located in the breast and armpit). Dry ear wax is associated with less-developed apocrine glands—therefore a gene coding for earwax could control development of apocrine glands and the nature of their secretory products.
Hiroaki Tomita (formerly of Nagasaki University School of Medicine, Japan) and colleagues were alerted by a Japanese woman with paroxysmal kinesigenic choreoathetosis (a neurological disorder characterised by intermittent uncontrollable twisting movements of the extremeties); the woman had wet ear wax (unusual for the Japanese population), and six other members of her family with the same neurological condition also had wet ear wax. From this, the investigators were able to identify the gene coding for ear wax as being located on the same area of chromosome 16 as the gene responsible for paroxysmal kinesigenic choreoathetosis.
Hiroaki Tomita comments: "The region to which we mapped the earwax locus is included in the region associated with paroxysmal kinesigenic choreoathetosis, therefore the two loci should be close to each other. Identification of the earwax locus could contribute to further anthropogenetic studies and to physiological and pathological understanding of apocrine-gland development."
Contact: Dr Hiroaki Tomita, Department of Psychiatry and Human Behaviour, University of California Irvine, D346 MED SCI I, Irvine, CA 92697-1675, USA; T) +1 949 824 9170; F) +1 949 824 7012; E) htomita@uci.edu
Journal
The Lancet