The neural pattern by which gustatory information is encoded has been the subject of debate for several decades. One view, the across fiber pattern model, maintains that taste qualities are represented by patterns of activity across populations of afferent nerves. In another view, the labeled-line model, taste qualities are encoded by particular subsets of taste receptor cells (TRCs) and the afferent neurons to which they synapse. The long-term objective of this research is to study the pattern of innervation of particular subsets of TRCs and determine if there is anatomical evidence for or against the existence of labeled lines in gustatory neural circuits. This will be done by expressing a lectin such as wheat germ agglutinin (WGA) in specific subsets of TRCs in transgenic mice and determining the pattern of labeling of afferent nerves and gustatory areas in the peripheral and central nervous systems. The research described in this application is a feasibility study intended to provide the tools needed to tackle this long-standing problem. We will produce transgenic mice expressing a red or green fluorescent protein marker (RFP or GFP) under the control of the promoter regions of T1R1, T1R3 and mT2R5, and determine by expression studies whether these promoters are able to target expression of heterologous genes specifically to discrete subsets of TRCs. We will also produce transgenic mice expressing WGA or a WGA-GFP fusion protein under the control of the (x-gustducin promoter and determine if these proteins will cross the synapse to migrate to first order and higher neurons. In future work designed to seek anatomical evidence for or against labeled lines, we will transgenically express differently tagged WGA proteins in two subsets of mouse taste receptor cells (for example, those expressing the bitter- responsive receptors (the T2Rs) and those expressing the candidate sweet receptor T1R3).
| Damak, Sami; Mosinger, Bedrich; Margolskee, Robert F (2008) Transsynaptic transport of wheat germ agglutinin expressed in a subset of type II taste cells of transgenic mice. BMC Neurosci 9:96 |
