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Show 225 THE UNIVERSITY OF UTAH Grooming is an innate behavior in mammals. The Hoxb8 gene mutation induces excessive grooming behavior in mouse models. The grooming is so excessive that it leads to hair loss and lesion formation and so is considered pathological. Hoxb8 cell lineage has only been detected in microglia in the brain (Chen et al). Dynamics within and between the microglial cells and other brain cell types may be responsible for the excessive grooming behaviors exhibited by the hoxb8 mutant mice. Behavioral analysis apparatus such as the plus maze, LABORAS, and open field test were used to examine differences in behaviors between the mutant and wild type mice. They have shown that hoxb8 mutants spend a significantly larger amount of time grooming than their wild-type counterparts. The mutants have also shown an element of heightened anxiety compared to the wild-type mice. Immunohistochemistry along with IMARIS software were used to count the number of microg-lia, examine its morphological structure, and examine its influences on surrounding struc-tures. Colocolization of GFP and Td-tomato suggests there are two populations of microglia, those expressing hoxb8 and those that are not. The subpopulation with hoxb8 accounts for 40% of microglia. We propose there is an OCD circuit, which encompasses neural connections between orbito-frontal areas, caudate and putamen areas and pre frontal areas based on human studies on OCD. The dynamics of Feed forward and feed back connectivities might play an important role in developing OCD phenotype. We suggest that there maybe some alterations in these connections via Hoxb8mutation, although further examination is required. Mechanisms are unknown as to what areas of the brain initiate and/or sustain grooming behavior; though, it can be inferred that hoxb8 microglia play a significant role in influencing neuronal activity and inducing the connectivity and neural circuit changes. Hoxb8 GENE MUTATION EFFECTS ON MOUSE MODEL BEHAVIOR Alexis Gosdis, (Naveen Nagarajan, Mario Capecchi) Department of Genetics University of Utah health sciences leap program Alexis Gosdis Naveen Nagarajan Mario Capecchi |