The Majority of Multipotent Epidermal Stem Cells Do Not Protect Their Genome by Asymmetrical Chromosome Segregation

The study, conducted on a total of 48 mice, examined the validity of the immortal strand hypothesis in hair follicle stem cells (SCs) by tracking DNA strand segregation using nucleotide analogs CldU and IdU. The hypothesis posits that SCs protect their genome by asymmetrically segregating their DNA strands during cell division. However, the study's findings contradicted this hypothesis, showing that the majority of hair follicle SCs do not employ asymmetrical chromosome segregation. Instead, chromosome segregation appears to occur randomly during development, tissue homeostasis, and SC activation. Label retention in these cells was associated with relative quiescence rather than asymmetric segregation. The study's results suggest that random DNA strand segregation might be a common mechanism in adult SCs, challenging the previously held belief that asymmetrical segregation is a means of protecting the genome in multipotent epidermal stem cells.