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Gain-of-function (GOF) mutations in the gene for signal transducer and activator of transcription 1 (STAT1) account for approximately one-half of patients with chronic mucocutaneous candidiasis (CMC) disease. Patients with GOF-STAT1 mutations display a broad variety of infectious and autoimmune manifestations in addition to CMC, and those with severe infections and/or autoimmunity have a poor prognosis. The establishment of safe and effective treatments based on a precise understanding of the molecular mechanisms of this disorder is required to improve patient care. To tackle this problem, we introduced the human R274Q GOF mutation into mice [GOF-Stat1 knock-in (GOF-Stat1R274Q)]. To investigate the immune responses, we focused on the small intestine (SI), which contains abundant Th17 cells. Stat1R274Q/R274Q mice showed excess phosphorylation of STAT1 in CD4+ T cells upon IFN-γ stimulation, consistent with the human phenotype in patients with the R274Q mutation. We identified two subpopulations of CD4+ T cells, those with 'normal' or 'high' level of basal STAT1 protein in Stat1R274Q/R274Q mice. Upon IFN-γ stimulation, the 'normal' level CD4+ T cells were more efficiently phosphorylated than those from WT mice, whereas the 'high' level CD4+ T cells were not, suggesting that the level of STAT1 protein does not directly correlate with the level of pSTAT1 in the SI. Inoculation of Stat1R274Q/R274Q mice with Candida albicans elicited decreased IL-17-producing CD4+RORγt+ cells. Stat1R274Q/R274Q mice also excreted larger amounts of C. albicans DNA in their feces than control mice. Under these conditions, there was up-regulation of T-bet in CD4+ T cells. GOF-Stat1R274Q mice thus should be a valuable model for functional analysis of this disorder., (© The Japanese Society for Immunology. 2019. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Alexander disease (AxD) is a neurodegenerative disease in astrocytes caused by a mutation in the gene encoding glial fibrillary acidic protein, GFAP. We herein present the case of a 12-year-old girl who showed intermittent exotropia at 3 years of age and central precocious puberty at 7 years of age. The periventricular and medulla oblongata showed high signal intensity on T2-weighted magnetic resonance imaging. The patient was diagnosed with AxD after direct sequencing revealing a de novo recurrent mutation, c.1246C>T (p.R416W) in GFAP. The transient expression of GFAP R416W in cells resulted in the significant formation of aggregates, which recapitulated the hallmark of AxD. We firstly utilized In Cell analyzer to prove the tendency of aggregate formation by mutants of GFAP., (Copyright © 2018 The Japanese Society of Child Neurology. Published by Elsevier B.V. All rights reserved.)