INTRODUCTION: While immune dysfunction has been increasingly linked to Alzheimer's disease (AD) progression, many major innate immune signaling molecules have yet to be explored in AD pathogenesis using genetic targeting approaches.METHODS: To investigate a role for the key innate immune adaptor molecule, stimulator of interferon genes (STING), in AD, we deleted Sting1 in the 5xFAD mouse model of AD‐related amyloidosis and evaluated the effects on pathology, neuroinflammation, gene expression, and cognition.RESULTS: Genetic ablation of STING in 5xFAD mice led to improved control of amyloid beta (Aβ) plaques, alterations in microglial activation status, decreased levels of neuritic dystrophy, and protection against cognitive decline. Moreover, rescue of neurological disease in STING‐deficient 5xFAD mice was characterized by reduced expression of type I interferon signaling genes in both microglia and excitatory neurons.DISCUSSION: These findings reveal critical roles for STING in Aβ‐driven neurological disease and suggest that STING‐targeting therapeutics may offer promising strategies to treat AD.Highlights: Stimulator of interferon genes (STING) deficiency in the 5xFAD mouse model of Alzheimer's disease‐related amyloidosis results in decreased amyloid beta (Aβ) deposition and altered microglial activation status. Protection against amyloidosis in STING‐deficient 5xFAD mice is associated with decreased expression of genes involved in type I IFN signaling, improved neuronal health, and reduced levels of oxidative stress. Loss of STING in 5xFAD mice leads to improved spatial learning and memory.

The X-linked neurodevelopmental diseases CDKL5 deficiency disorder (CDD) and Rett syndrome (RTT) are associated with intellectual disability, infantile spasms and seizures. Although mitochondrial dysfunction has been suggested in RTT, less is understood about mitochondrial function in CDD. A comparison of bioenergetics and mitochondrial function between isogenic wild-type and mutant neural progenitor cell (NPC) lines revealed increased oxygen consumption in CDD mutant lines, which is associated with altered mitochondrial function and structure. Transcriptomic analysis revealed differential expression of genes related to mitochondrial and REDOX function in NPCs expressing the mutant CDKL5. Furthermore, a similar increase in oxygen consumption specific to RTT patient–derived isogenic mutant NPCs was observed, though the pattern of mitochondrial functional alterations was distinct from CDKL5 mutant–expressing NPCs. We propose that aberrant neural bioenergetics is a common feature between CDD and RTT disorders. The observed changes in oxidative stress and mitochondrial function may facilitate the development of therapeutic agents for CDD and related disorders.

Microglia, the resident brain immune cells, play a critical role in normal brain development, and are impacted by the intrauterine environment, including maternal immune activation and inflammatory exposures. The COVID-19 pandemic presents a potential developmental immune challenge to the fetal brain, in the setting of maternal SARS-CoV-2 infection with its attendant potential for cytokine production and, in severe cases, cytokine storming. There is currently no biomarker or model for in utero microglial priming and function that might aid in identifying the neonates and children most vulnerable to neurodevelopmental morbidity, as microglia remain inaccessible in fetal life and after birth. This study aimed to generate patient-derived microglial-like cell models unique to each neonate from reprogrammed umbilical cord blood mononuclear cells, adapting and extending a novel methodology previously validated for adult peripheral blood mononuclear cells. We demonstrate that umbilical cord blood mononuclear cells can be used to create microglial-like cell models morphologically and functionally similar to microglia observed in vivo. We illustrate the application of this approach by generating microglia from cells exposed and unexposed to maternal SARS-CoV-2 infection. Our ability to create personalized neonatal models of fetal brain immune programming enables non-invasive insights into fetal brain development and potential childhood neurodevelopmental vulnerabilities for a range of maternal exposures, including COVID-19.

Microglia dysregulation is implicated across a range of neurodevelopmental and neurodegenerative disorders, making their modulation a promising therapeutic target. Using PBMC-derived induced microglia-like cells (piMGLCs) in a scalable assay, we screened 489 CNS-penetrant compounds for modulation of microglial phagocytosis of human synaptosomes in a validated assay for microglia-mediated synaptic pruning. Compounds from the library that reduced phagocytosis by ≥2 standard deviations across the library without cytotoxicity were validated in secondary screens, with 28 of them further confirmed to reduce phagocytosis by 50% or more. These compounds comprise a wide range of therapeutic classes with different mechanisms of action, including immunosuppressants, kinase inhibitors, antipsychotics, and epigenetic modulators. Image-based morphological measurements were calculated to measure the degree of ramified vs. ameboid morphotypes as an indicator of activation state. Additionally, transcriptomic profiling indicated divergent effects on cell signaling, metabolism, activation, and actin dynamics across confirmed compounds. In particular, multiple CNS-penetrant small molecules with prior FDA approval or demonstration of safety in vivo demonstrated modulatory effects on microglia. For example, identified drugs such as the tyrosine kinase inhibitors lapatinib, alectinib, and lazertinib and the epigenetic modulator vorinostat have been approved for various cancer treatments and are being investigated for other indications; however, they have not been extensively studied in patients for neurodevelopmental and neurodegenerative disorders. These potential disease-modifying agents represent high-priority candidates for repositioning studies in neurodevelopmental, neuroinflammatory, or neurodegenerative disorders.

Genotoxic stress, which includes DNA damage and the mis-localization of DNA and RNA, is a defining feature of tauopathies, Alzheimer’s disease, and several other neurodegenerative disorders. Recent findings indicate that activation of the innate immune system in response to genotoxic stress can drive harmful neuroinflammation, compromise neuronal integrity, and promote neurodegeneration. Multiple innate immune sensors of genotoxic stress have recently been discovered, but the contributions of many of these emerging nucleic acid–sensing pathways in neurodegenerative disease pathogenesis remain largely unexplored. Z-DNA binding protein 1 (ZBP1) is one such recently discovered genotoxic stress sensor that has been shown to incite various forms of cell death as well as proinflammatory cytokine production in response to left-handed Z conformations of DNA (Z-DNA) and RNA (Z-RNA). Here, we show that ZBP1 deletion provides protection against tau pathology and neuronal loss in the PS19 mouse model of tauopathy. Moreover, we find that this rescue of tauopathy seen with ZBP1 ablation is associated with dampened activation of microglia and astrocytes. These findings identify ZBP1 as a pivotal genotoxic stress sensor that drives tau pathology, gliosis, and neuronal loss in tauopathy. This work further suggests that targeting ZBP1 may offer a therapeutic strategy to treat tau-mediated neurodegenerative disease.