Deciphering the precise in vivo function of a particular neuronal subpopulation is one of the most challenging issues in neurobiology. Dorsal root ganglia (DRG) neurons represent a powerful model system to address this fundamental question. These neurons display many morphological, anatomical and few molecular characteristics. With the aim of expanding the molecular description of the primary sensory neurons, we used Affimetrix microarrays to compare global gene expression profiles of DRG of wild type and trkA(trkC/trkC) knock-in mice at birth and identified several hundred potential markers of nociceptive neurons and few markers of proprioceptive neurons. Here, we describe the identification of two members of a family of putative adapter proteins STAC1 and STAC2. We found STAC1 and STAC2 being expressed in a mutually exclusive fashion in adult DRG neurons. STAC1 mainly marks peptidergic nociceptive neurons while STAC2 is expressed in a subset of nonpeptidergic nociceptors, in all trkB+ neurons and in a subpopulation of proprioceptive neurons. Our expression data demonstrate that STAC proteins identify four categories of primary sensory neurons; one class of peptidergic neurons, a subset of nonpeptidergic neurons, all TrkB+neurons and a subset of proprioceptive neurons. Genetic marking of STACs-expressing sensory neurons will lend significant advance into our understanding of DRG neuronal functional diversity.
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