Recent studies have demonstrated that immune cells play an important role in the pathogenesis of many neurological conditions. Immune cells constantly survey the brain microvasculature for irregularities in levels of factors that signal homeostasis. Immune responses are initiated when necessary, resulting in mobilisation of the microglial cells resident in the central nervous system (CNS) and/or of infiltrating peripheral cells. However, little is known about the kinetics of immune cells in healthy and diseased CNS, because it is difficult to perform long-term visualisation of cell motility in live tissue with minimal invasion. Here, we describe highly sensitive in vivo MRI techniques for sequential monitoring of cell migration in the CNS at the single-cell level. We show that MRI combined with intravenous administration of super-paramagnetic particles of iron oxide (SPIO) can be used to monitor the transmigration of peripheral phagocytes into healthy or LPS-treated mouse brains. We also demonstrate dynamic cell migration in live animal brains with time-lapse MRI videos. Time-lapse MRI was used to visualise and track cells with low motility in a control mouse brain. High-sensitivity MRI cell tracking using SPIO offers new insights into immune cell kinetics in the brain and the mechanisms of CNS homeostasis.

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Dysregulation in dopaminergic neurotransmission might play a role in the pathogenesis of schizophrenia, and therefore genetic components of the dopamine (DA) pathway may confer risk. The NR4A2 (Nurr1) gene is essential for the development and maintenance of mesencephalic DA-synthesizing neurons. Moreover, Nurr1 forms a heterodimer with the retinoid X receptor and disturbances in the retinoid-signaling cascade may be involved in susceptibility to schizophrenia. To investigate the potential genetic contribution of NR4A2, we performed a case-control association study using three common variants in the gene [-2922(C)2-3, IVS6 + 17 approximately +18insG, EX8 + 657(CA)9-10] that were in strong linkage disequilibrium with each other. We did not detect a significant allelic or genotypic association. Haplotypes derived from all three polymorphisms generated similar results. These data do not support the notion that the NR4A2 gene plays a major role in risk for schizophrenia among Japanese individuals.

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