Of the vertebrate senses, touch is the least understood at the molecular le
vel. The ion channels that form the core of the mechanosensory complex and
confer touch sensitivity remain unknown(1-3). However, the similarity of th
e brain sodium channel 1 (BNC1)(4-6) to nematode proteins involved in mecha
notransduction 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 s
ensitivity of a specific component of mechanosensation: low-threshold rapid
ly adapting mechanoreceptors. In rodent hairy skin these mechanoreceptors a
re excited by hair movement(2). Consistent with this function, we found BNC
1 in the lanceolate nerve endings that lie adjacent to and surround the hai
r 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 respon
se of acid-stimulated nociceptors were normal in BNC1 null mice. These data
identify the BNC1 channel as essential for the normal detection of light t
ouch and indicate that BNC1 may be a central component of a mechanosensory
complex.