Identification of cytoskeletal markers for the different microvilli and cell types of the rat vomeronasal sensory epithelium

The vomeronasal organ (VNO) of the mammal nose is specialized to detect phe romones. The presumed site of the chemosensory signal transduction of phero mones is the vomeronasal brush border of the VNO sensory epithelium, which has been shown to contain two different sets of microvilli: (i) the tall mi crovilli of supporting cells and (ii) the short microvilli of the chemorece ptive VNO neurons that branch and intermingle with the basal portions of th e longer supporting cell microvilli. A key problem when studying the subcel lular distribution of possible VNO signal transduction molecules at the lig ht microscope level is the clear discrimination of immunosignals derived fr om dendritic microvilli of the VNO neurons and surrounding supporting cell structures. In the present study we therefore looked for cytoskeletal marke r proteins, that might help to distinguish at the light microscope level be tween the two sets of microvilli. By immunostaining we found that the VNO d endritic microvilli can be selectively labelled with antibodies to the calc ium-sensitive actin filament-bundling protein villin, whereas supporting ce ll microvilli contain the actin filament cross-linking protein fimbrin, but not villin. Useful cytoplasmic marker molecules for cellular discriminatio n were cytokeratin 18 for supporting cells and beta -tubulin for dendrites of VNO neurons. A further finding was that the non-sensory epithelium of th e rat VNO contains brush cells, a cell type that appears to be involved in certain aspects of chemoreception in the gut. Brush cells or other structur es of the vomeronasal brush border did not contain alpha -gustducin.