The mammalian sodium channel BNC1 is required for normal touch sensation

Of the vertebrate senses, touch is the least understood at the molecular level. The ion channels that form the core of the mechanosensory complex and confer touch sensitivity remain unknown(1-3). However, the similarity of the brain sodium channel 1 (BNC1)(4-6) to nematode proteins involved in mechanotransduction indicated that it might be a part of such a mechanosensor(7,8). Here we show that disrupting the mouse BNC1 gene markedly reduces the sensitivity of a specific component of mechanosensation: low-threshold rapidly adapting mechanoreceptors. In rodent hairy skin these mechanoreceptors are excited by hair movement(2). Consistent with this function, we found BNC1 in the lanceolate nerve endings that lie adjacent to and surround the hair follicle(9). Although BNC1 has been proposed to have a role in pH sensing(10,11), the acid-evoked current in cultured sensory neurons and the response of acid-stimulated nociceptors were normal in BNC1 null mice. These data identify the BNC1 channel as essential for the normal detection of light touch and indicate that BNC1 may be a central component of a mechanosensory complex.