The cellular basis of mechanosensory Merkel-cell innervation during development

• Main Authors: Blair A Jenkins, Natalia M Fontecilla, Catherine P Lu, Elaine Fuchs, Ellen A Lumpkin
• Format: Article
• Language: English
• Published: eLife Sciences Publications Ltd 2019-02-01
• Series: eLife
• Subjects: touch; skin; somatosensory neuron; mechanoreceptor; dorsal root ganglion; hair follicle
• Online Access: https://elifesciences.org/articles/42633

Touch sensation is initiated by mechanosensory neurons that innervate distinct skin structures; however, little is known about how these neurons are patterned during mammalian skin development. We explored the cellular basis of touch-receptor patterning in mouse touch domes, which contain mechanosensory Merkel cell-neurite complexes and abut primary hair follicles. At embryonic stage 16.5 (E16.5), touch domes emerge as patches of Merkel cells and keratinocytes clustered with a previously unsuspected population of Bmp4-expressing dermal cells. Epidermal Noggin overexpression at E14.5 disrupted touch-dome formation but not hair-follicle specification, demonstrating a temporally distinct requirement for BMP signaling in placode-derived structures. Surprisingly, two neuronal populations preferentially targeted touch domes during development but only one persisted in mature touch domes. Finally, Keratin-17-expressing keratinocytes but not Merkel cells were necessary to establish innervation patterns during development. These findings identify key cell types and signaling pathways required for targeting Merkel-cell afferents to discrete mechanosensory compartments.