The mystery surrounding the developmental origin of specialized skin cells involved in touch sensation appears to have been solved by scientists.
Merkel cells are neuroendocrine cells that reside in the vertebrate epidermis, passing mechanical stimuli on to sensory neurons.
In mice, they are mainly found in the paws and around the whiskers but, because they express proteins characteristic of both epithelial and neuronal cells.
It has long been debated whether Merkel cells develop from the epidermis or neural crest.
Van Keymeulen et al. traced the lineage of Merkel cells by fluorescently labeling cells derived from either epidermal or neural crest progenitors.
The researchers found that Merkel cells originally emerge from the embryonic epidermis.
In addition, epidermal stem cells in adult mouse skin replenish the Merkel cell population as they slowly die off over time.
The researchers also found that a transcription factor called Atoh1 is required for epidermal progenitors to differentiate into Merkel cells-mice lacking Atoh1 in their skin failed to develop any of the mechanotransducing cells.
According to senior author Cedric Blanpain, Atoh1 also acts as a tumour suppressor to prevent an aggressive skin cancer called Merkel cell carcinoma.
The findings appear online in the Journal of Cell Biology.