Merkel cells

Abstract

Merkel cells are post-mitotic cells scattered throughout the epidermis of vertebrates. They are particularly interesting because of the close connections that they develop with sensory nerve endings and the number of peptides they can secrete. These features suggest that they may make an important contribution to skin homeostasis and cutaneous nerve development. However, these cells remain mysterious because they are difficult to study. They have not been successfully cultured and cannot be isolated, severely hampering molecular biology and functional analysis. Merkel cells probably originate in the neural crest of avians and mammalians, and their "spontaneous" appearance in the epidermis may be caused by a neuron-independent epidermal differentiation process. Their functions are still unclear: they take part in mechanoreception or at least interact with neurons, but little is known about their interactions with other epidermal cells. This review provides a new look at these least-known cells of the skin. The numerous peptides they synthesize and release may allow them to communicate with many cells other than neurons, and it is plausible that Merkel cells play a key role in skin physiology and physiopathology.

Development and Homeostasis of the Skin Epidermis

“…MCs are neuroendocrine cells that can be found in hairy and glabrous skin. They are clustered in touch-sensitive areas called touch domes (Boulais and Misery 2007). MCs express intermediate filaments of simple epithelia, such as K8, K18, and K20, as well as neuropeptides, proneural transcription factors, and components of presynaptic machinery, suggesting that MCs arise from neural crest cells.…”

Epidermal progenitors give rise to Merkel cells during embryonic development and adult homeostasis

“…3 B). In one The developmental origin of MCs has remained controversial since their discovery in 1875 (Moll et al, 2005;Boulais and Misery, 2007;Lucarz and Brand, 2007). One hypothesis suggests that MCs are derived from neural crest cells (NCCs; Winkelmann, 1977) because MCs are excitable cells that synthesize neuropeptides and express presynaptic molecules and proneural transcription factors cells like many other neural crest-derived cells.…”

“…MCs reside in the vibrissae and dorsal and ventral parts of the skin epidermis as well as in the paw epidermis (Moll et al, 2005;Boulais and Misery, 2007;Lucarz and Brand, 2007). Using antibodies that specifically recognize MCs (Kim and Holbrook, 1995;Moll et al, 1995;Vielkind et al, 1995), MCs were first detected in the whisker region around embryonic day (E) 15, whereas in the back skin and in the paw epidermis, MCs were detected at E17 ( Fig.…”

“…MCs are neuroendocrine cells present in the basal layer of the epidermis of vertebrates (Moll et al, 2005;Boulais and Misery, 2007;Lucarz and Brand, 2007). MCs are clustered in touch-sensitive zones of the glabrous and hairy skin, called touch domes, and are densely innervated by slowly adapting type I mechanoreceptor nerve fibers.…”

Responses of hair follicle–associated structures to loss of planar cell polarity signaling

“…APM contraction pivots the follicle about its point of insertion at the skin surface so that the follicle assumes a more nearly vertical orientation. The Merkel cell complex consists of afferent nerve endings and an associated semicircle of specialized epidermal derivatives that surround the largest follicles [guard or tylotrich hairs (3)(4)(5)]. Like primary auditory hair cells, with which they share a number of molecular attributes, Merkel cells appear to act as mechanosensors (6).…”