Anxiety-associated behaviors following ablation of Miro1 from cortical excitatory neurons
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Autism spectrum disorder, schizophrenia, and bipolar disorder are neuropsychiatric disorders that manifest early in life with a wide range of phenotypes, including repetitive behavior, agitation, and anxiety (American Psychological Association, 2013). While the etiology of these disorders is not completely understood, recent data implicate a role for mitochondrial dysfunction. To function optimally mitochondria must translocate to metabolically active intracellular compartments to support energetics and free-radical buffering; failure to achieve this localization results in cellular dysfunction (Picard et al., 2016). Mitochondrial Rho-GTPase 1 ( Miro1 ) resides on the outer mitochondrial membrane and participates in neuronal microtubule-mediated mitochondrial motility and homeostasis (Fransson et al., 2003). Previous research implicates the loss of MIRO1 as a contributor to the onset/progression of neurodegenerative diseases including amyotrophic lateral sclerosis, Alzheimer’s disease, and Parkinson’s disease (Kay et al., 2018). We have hypothesized that MIRO1 also has a role in nervous system development and function (Lin-Hendel et al., 2016). To test this, we ablated Miro1 from cortical excitatory progenitors by crossing floxed Miro1 mice with Emx1-cre mice. We found that mitochondrial mis-localization in migrating excitatory neurons was associated with reduced brain weight, decreased cortical volume, and subtle disruptions in cortical organization. Adult Miro1 conditional mutants exhibit agitative-like behaviors, including decreased nesting behavior and abnormal home cage activity. Open field testing revealed anxiety-like behavior and elevated plus maze and wide/narrow box testing found the mice avoided confined spaces. Our data link MIRO1 function with mitochondrial dynamics in the pathogenesis of several neuropsychiatric disorders and implicate mitochondrial localization in anxiety-like behaviors.
Significance
Neuropsychological disorders such as autism spectrum disorder, schizophrenia, and bipolar disorder have overlapping symptoms and behaviors. While the mechanisms underlying these disorders are not completely understood, recent evidence suggests mitochondrial dysfunction and mis-localization within a cell could play a role. Mitochondria are organelles that provide energy and other self-regulating processes to the cell. Previous research from our lab has shown distinct dynamic localization patterns within migrating excitatory and inhibitory neurons may be important during development. To further examine the importance of mitochondrial localization, we ablated MIRO1, a protein important for coupling mitochondria to motor proteins, in excitatory neurons. Mitochondria mis-localize in migrating excitatory neurons, and this is associated with a loss of motor skills and anxiety-like behavior in post-natal mice.
