Age and differentiation-related differences in neuron-specific tubulin immunostaining of olfactory sensory neurons

Olfactory sensory neurons (OSNs) are unusual mammalian neurons because they are produced continually throughout adult life and because their production is upregulated after injury. Because OSNs also have an unusual immunological profile and do not bind the commonly used antibody markers for neurons, we sought new antibody markers for studies of OSN regeneration. In this report, we characterize the staining patterns of antibodies to the Class III beta, neuron-specific, tubulin (NST) in rat olfactory tissue sections, to determine if these antibodies specifically label OSNs. In tissue sections from newborn rats, monoclonal antibodies to NST labeled cell bodies and processes of both immature (olfactory marker protein, OMP, -negative) and mature (OMP-positive) OSNs. In tissue sections from adult rats, immature OSNs showed both cell body and dendrite staining with anti-NST, while mature OSNs showed little or no cell body staining. Mature OSNs appeared to have both axonal and dendritic anti-NST staining. Axonal staining was suggested by the complete labeling of the olfactory nerve bundles and the nerve fiber layer of the olfactory bulb. The extent of labeling was judged by comparison with anti-OMP staining. Mature OSN dendritic staining was suggested because a much higher number of dendrites were anti-NST stained in the epithelium than cell bodies. These changes suggest both age and differentiation-related changes in subcellular distribution of NST in OSNs. NST antibodies are thus good markers for all OSNs in the newborn rat, but selective markers for immature OSNs and mature OSN processes in the adult rat. NST antibodies may also be useful probes for beta III tubulin function in neurons.