Merkel Cells Are Essential for Light-Touch Responses

Mysterious Merkel cells Anatomists have known about the existence of Merkel cells in our skin for over a century. However, the function of these cells has been unclear and controversial. To solve this mystery, Maricich et al. (p. 1580) created a genetic deletion of Merkel cells. When Atoh1, a transcription factor expressed by Merkel cells, was conditionally deleted in the skin, Merkel cells were completely absent from Atoh1CKO mice. Using ex vivo skin and nerve preparations from the animals showed that Merkel cells are needed to properly encode light touch sensation in the skin. In the skin, special cells with specific properties endow their afferent nerves with the ability to resolve fine spatial details. The peripheral nervous system detects different somatosensory stimuli, including pain, temperature, and touch. Merkel cell-neurite complexes are touch receptors composed of sensory afferents and Merkel cells. The role that Merkel cells play in light-touch responses has been the center of controversy for over 100 years. We used Cre-loxP technology to conditionally delete the transcription factor Atoh1 from the body skin and foot pads of mice. Merkel cells are absent from these areas in Atoh1CKO animals. Ex vivo skin/nerve preparations from Atoh1CKO animals demonstrate complete loss of the characteristic neurophysiologic responses normally mediated by Merkel cell-neurite complexes. Merkel cells are, therefore, required for the proper encoding of Merkel receptor responses, suggesting that these cells form an indispensible part of the somatosensory system.