Selective expression of glionexin, a glial glycoprotein, in insect mechanoreceptors.

The distribution of a glial cell-associated glycoprotein, glionexin (GX), on sensory receptors of the adult cricket Acheta domesticus is described, using the monoclonal antibody 5B12 as an immunohistochemical probe. GX was previously shown to be widely distributed in the embryo and to persist in the postembryonic to adult central nervous system. Here we demonstrate that it is restricted in the adult periphery to three subclasses of mechano-receptor sensilla: large socketed hair mechanoreceptors, their associated campaniform sensilla, and chordotonal organs. GX was not detected in photoreceptors, chemoreceptors, or other mechanoreceptors. The pattern of distribution differs significantly within the three subclasses of mechanoreceptors. In the hair and campaniform receptors GX is restricted to the extracellular space among glial cells clustered around the axon hillock region, but in chordotonal organs it surrounds the scolopidium at the tip of dendrites. The highly restricted distribution of GX in the periphery suggests possible functions that include mechanical stability of the sensory apparatus and ionic homeostasis in the respective neuronal spike-generating regions. The developmental modulation of GX expression is taken to imply multiple functions for the molecule during the life of the insect.