Some aspects of the use of hair follicles for the biochemical study of inborn errors of metabolism

The root of a hair which has been plucked from the scalp is surrounded by three or four layers of cells which have been avulsed from the hair follicle (Fig. 1). Hairs begin to develop when the foetus is 5–6 weeks old. Each hair follicle develops from a small group of ectodermal cells which grows into the subjacent mesoderm, and there is an appreciable probability that this group of cells will in turn have been derived from a single cell. Under these circumstances the follicles would be clonal. The random inactivation of one X-chromosome in females (Lyon, 1962) together with the suggestion that hair follicle cells are clonal led to the prediction that the heterozygous carriers of a sex-linked enzyme variant would show two classes of hair follicles containing the normal and the abnormal enzyme respectively. Gartler, Gandini, Angioni and Argiolas (1969) studied the isoenzyme composition of hair follicles from a subject who was heterozygous for the fast and slow moving electrophoretic variants of d-glucose-6-phosphate: NADP+oxidore-ductase (EC 1.1.1.49) (glucose-6-phosphate dehydrogenase or G6PD). They found three classes of hair follicle, which contained: the fast migrating, the slowly migrating and both variants respectively. These results confirmed that it would be possible to use hair follicles to determine the genetic status of a subject who might be a carrier of a sex linked defect of an enzyme which is normally present in the cells around the root of a hair. They also indicated that sufficient hairs would have to be examined to allow for the imperfect cloning of the follicles.