Ectopic Atoh1 Expression Drives Merkel Cell Production in Embryonic, Postnatal, and Adult Epidermis

The study demonstrated that ectopic expression of the transcription factor Atoh1 was sufficient to induce the production of Merkel cells in the epidermis of transgenic mice. In embryos, Atoh1 expression led to widespread expression of the Merkel cell marker keratin 8 (K8) throughout the epidermis. In adolescent mice, K8 expression was widespread in glabrous skin but confined to hair follicles in other areas. Ectopic K8+ cells developed characteristics of mature Merkel cells, although their numbers decreased over time, with some persisting in hair follicles. In adult mice, more ectopic K8+ cells were produced during the anagen phase of the hair cycle and when Notch signaling was disrupted. The study concluded that Atoh1 expression could generate new Merkel cells, with epidermal cell competency influenced by skin location, developmental age, hair cycle stage, and Notch signaling.