【Background】Mutations in colony-stimulating factor 1 receptor (CSF1R) are known to cause adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP), which has been recently demonstrated as a primary microgliopathy characterized by cognitive impairment. Although the molecular mechanism underlying CSF1R-medi?ated microgliopathy remains unclear, therapeutic strategies have generally targeted modulation of microglial function. In particular, the microglial inhibitor, minocycline, has been shown to attenuate learning and memory defcits in several neurodegenerative diseases. The objectives of this study were to investigate the pathogenic mechanisms underlying ALSP and to explore the therapeutic efects of minocycline in an in vivo model of ALSP. We hypothesized that inhibiting microglial activation via minocycline could reverse the behavior and pathological defects in ALSP model mice.

【Methods】We generated a Csf1r haploinsufciency mouse model of ALSP using CRISPR/Cas9 genome editing and conducted electrophysiological recordings of long-term potentiation (LTP) and behavioral tests to validate the recapitulation of clinical ALSP characteristics in 8- to 11-month-old mice. RNA-sequencing was used to explore enriched gene expression in the molecular pathogenesis of ALSP. Microglial activation was assessed by immunofuorescent detection of Iba1 and CD68 in brain sections of male ALSP mice and pro-infammatory activation and phagocytosis were assessed in Csf1r^+/? microglia. Therapeutic efects were assessed by behavioral tests, histological analysis, and morphological examination after four weeks of intraperitoneal injection with minocycline or vehicle control in Csf1r^+/? mice and wild-type control littermates.

【Materials and methods】In brief, diluted samples were analyzed on the AST-Sc-Lite (a fully auto single-molecule detection machine supplied by Suzhou AstraBio Technology Co., Ltd.).

【Results】我We found that synaptic function was reduced in LTP recordings of neurons in the hippocampal CA1 region,while behavioral tests showed impaired spatial and cognitive memory specifcally in male Csf1r^+/? mice. Increased activation, pro-infammatory cytokine production, and enhanced phagocytic capacity were also observed in Csf1r^+/? microglia. Treatment with minocycline could suppress the activation of Csf1r+/? microglia both in vitro and in vivo. Notably, the behavioral and pathological defcits in Csf1r^+/? mice were partially rescued by minocycline administration, potentially due to inhibition of microglial infammation and phagocytosis in Csf1r^+/? mice.

【Conclusions】Our study shows that CSF1R defciency results in aberrant microglial activation, characterized by a pro-infammatory phenotype and enhanced phagocytosis of myelin. Our results also indicate that microglial inhibition by minocycline can ameliorate behavioral impairment and ALSP pathogenesis in CSF1R-defcient male mice, suggesting a potential therapeutic target for CSF1R-related leukoencephalopathy. Collectively, these data support that minocycline confers protective efects against CSF1R-related microgliopathy in male ALSP model mice.

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