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 Seat Products 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 Collar mechanosensory compartments.