Résumé
The molecular mechanism whereby vertebrate primary sensory neurons convert mechanical energy at their receptive fields into action potentials is unknown. In recent years, genetic screens for touch insensitive mutants of the nematode worm Caenorhabditis elegans have led to the identification of several genes required for mechanical sensitivity. A model has been proposed in which a mechanically gated ion channel is connected both to the extracellular matrix and to the cytoskeleton. Displacement of the membrane is proposed to produce a shearing force that pulls the channel open. MEC-2 is thought to play an important role in this complex by linking the ion channel to the cytoskeleton. MEC-2 is highly homologous to a vertebrate protein called stomatin. Stomatin was first isolated from erythrocytes where it is a major integral membrane protein. To date, however, no data on neuronal expression of stomatin in the peripheral nervous system (PNS) or central nervous system (CNS) is available. Here, we have used RT-PCR, in situ hybridization, Northern blotting, and immunocytochemistry to demonstrate that stomatin is expressed by all sensory neurons in mouse dorsal root ganglia. Indirect immunofluorescence together with transfection of cultured adult sensory neurons with epitope-tagged stomatin show that stomatin is localized in spots on somatic and axonal membranes. During development, stomatin begins to be expressed by sensory neurons only as target innervation occurs. The onset of expression of stomatin thus coincides with the onset of functional mechanical sensitivity. Together, our data suggest that stomatin, like the C. elegans MEC-2 gene, is expressed in an appropriate temporal and spatial manner to participate in a putative vertebrate mechanotransduction complex.