The Cellular and Molecular Basis of Direction Selectivity of Aδ-LTMRs

• Aδ-LTMRs are tuned to deflection of body hairs in the rostral-to-caudal direction
• Aδ-LTMR lanceolate endings around hair follicles are polarized to the caudal side
• Epithelia BDNF is synthesized on the caudal, but not rostral, side of hair follicles
• Polarization of Aδ-LTMR lanceolate endings mediates Aδ-LTMR direction selectivity

SummaryThe perception of touch, including the direction of stimulus movement across the skin, begins with activation of low-threshold mechanosensory neurons (LTMRs) that innervate the skin. Here, we show that murine Aδ-LTMRs are preferentially tuned to deflection of body hairs in the caudal-to-rostral direction. This tuning property is explained by the finding that Aδ-LTMR lanceolate endings around hair follicles are polarized; they are concentrated on the caudal (downward) side of each hair follicle. The neurotrophic factor BDNF is synthesized in epithelial cells on the caudal, but not rostral, side of hair follicles, in close proximity to Aδ-LTMR lanceolate endings, which express TrkB. Moreover, ablation of BDNF in hair follicle epithelial cells disrupts polarization of Aδ-LTMR lanceolate endings and results in randomization of Aδ-LTMR responses to hair deflection. Thus, BDNF-TrkB signaling directs polarization of Aδ-LTMR lanceolate endings, which underlies direction-selective responsiveness of Aδ-LTMRs to hair deflection.PaperClip To listen to this audio, enable JavaScript on your browser. However, you can download and play the audio by clicking on the icon belowHelp with MP3 filesOptionsDownload audio (3833 K)

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