Figure 3. Model of olfactory function in wild type and Chd7^Gt/+ mice.

Following inhalation, odorants are detected in the olfactory epithelium by binding to specific odorant receptors located on the surface of olfactory cilia. Bound odorants activate olfactory sensory neurons, which are bipolar neurons that project axons to the glomeruli in the olfactory bulb. Each olfactory sensory neuron (ex. blue, red, green, and purple) contains one type of odorant receptor in the cilia and each neuron with that type of odorant receptor projects an axon to the same glomerulus in the olfactory bulb. Electrical signals sent by olfactory sensory neurons are detected by mitral cell dendrites in the glomeruli. These signals are then sent to higher brain regions in the central nervous system. Wild type mouse olfactory epithelium contains densely packed olfactory sensory neurons which project to the olfactory bulb. However, Chd7^Gt/+ young adult mice have 30% fewer olfactory sensory neurons and olfactory bulb hypoplasia. We hypothesize that aged Chd7^Gt/+ mice have a greater reduction in both olfactory sensory neurons and size of the olfactory bulb.