The present invention is directed to methods for readily propagating somatic hair follicle stem cells or melanocyte stem cells. The methods comprise enhancing guanine nucleotide (GNP) biosynthesis, thereby expanding guanine nucleotide pools. This in turn conditionally suppresses asymmetric cell kinetics in the explanted cells. The methods of the invention include pharmacological methods and genetic methods. For example, the resulting cultured somatic hair follicle stem cells can be used for a variety of applications including cell replacement therapies such as hair transplants, gene therapies, and tissue engineering applications, such as the generation of artificial skin and skin regeneration strategies including skin grafts.