Amal Kachour
Research Mentor(s): Michael Roberts
Mentor Department: Otolaryngology-Head and Neck Surgery
Authors: Amal Kachour, Elie Huez, Michael Roberts
Session: Session 5 (2:00pm – 2:50pm)
Presentation Type: Poster 11
Abstract
The inferior colliculus (IC) is the midbrain hub of the central auditory pathway. The IC receives ascending and descending auditory inputs and is an important center for auditory computations. The IC sends auditory signals to higher and lower brain regions and also plays a role in non-auditory processing through projections to somatosensory and motion-related brain circuits. A gap in the field remains in understanding whether individual IC neuron types maintain consistent long-range projection patterns. This gap has persisted due to the challenge of selectively targeting IC neuron types for anatomical studies. Recently our lab identified secreted phosphoprotein 1 (SPP1) as a molecular marker for a subpopulation of IC neurons that is distinct from the IC neuron types previously identified by molecular markers. Our preliminary data suggest that SPP1 is densely distributed in the central nucleus of the IC, which sends a large projection to the medial geniculate body of the thalamus, the next station in the ascending auditory pathway. Thus, we hypothesize that SPP1 neurons in the IC primarily project to the medial geniculate body. To test this hypothesis, we conducted stereotaxic injections into the IC of SPP1-Cre mice with a Cre-dependent adeno-associated virus containing a construct for both membrane-bound GFP (mGFP) and mRuby-tagged synaptophysin. mGFP expression labeled the cell bodies, dendrites, and axons of SPP1 IC neurons. mRuby expression labeled SPP1 IC presynaptic sites along the axon. This approach allowed for the differentiation of individual SPP1 neuron morphologies (GFP) and patterns of SPP1 neuron postsynaptic targets (Ruby). Imaging and analysis were conducted in the medial geniculate body to uncover the long-range axonal projection patterns of individual SPP1 IC neurons. Identifying the patterns of SPP1 long-range projections provides the foundation for understanding the role that SPP1 neurons have in IC auditory computations.
