Title: Cellular and Molecular Mechanisms of Mammalian Touch-Dome Development
Description: Touch sensation is initiated by diverse mechanosensory neurons that innervate distinct skin structures; however, little is known about how touch receptors are patterned during mammalian skin development. During the course of my PhD training, I analyzed embryonic and neonatal development of mouse touch domes, which contain Merkel cell-neurite complexes that encode pressure and object features. I found that developing touch domes share three key features with canonical sensory placodes: discrete patches of specialized epithelial, co-clustered mesenchymal cells capable of engaging in molecular crosstalk with the epithelium, and selective recruitment of sensory neurons. During embryogenesis, molecularly distinct patches of epithelial Merkel cells and keratinocytes clustered with a previously unsuspected population of BMP4-expressing dermal fibroblasts in nascent touch domes. Concurrently, two populations of sensory neurons preferentially targeted touch domes compared with other skin regions.

Surprisingly, only one neuronal population persisted in mature touch domes. Overexpression of Noggin, a BMP antagonist, in epidermis at embryonic age 14.5 resulted in fewer touch domes, a loss of Merkel cells, and decreased innervation density in skin areas where touch domes are typically found. Thus, touch domes bear hallmarks of placode-derived sensory epithelia that require BMP signaling for proper specification.