Project description:Early- and late-onset forms of Alzheimer’s disease (AD) share common features that include abnormalities in lipid metabolism, immune response and synaptic function. Of these, the role of lipids remains the least understood. Our study revealed that molecular functions related to Stearoyl-CoA Desaturase (SCD), the rate limiting enzyme in monounsaturated fatty acid synthesis were specifically altered in the hippocampus of 3xTg-AD (a model of early-onset AD). Remarkably, infusion of an SCD inhibitor (SCDi) reversed 40% of altered immune and synapse genes, rescue dendritic spine number and structure, recovered activity-associated immediate-early gene expression and restored learning and memory in 3xTg-AD mice. In addition, we employed single cell RNA sequencing to characterize the cellular landscape of microglia subpopulations within the 3xTg hippocampus and uncovered that SCDi reversed microglial activation and polarization. Together, we show that a single lipid enzyme, SCD, impinges on the core features of AD.
Project description:Early- and late-onset forms of Alzheimer’s disease (AD) share common features that include abnormalities in lipid metabolism, immune response and synaptic function. Of these, the role of lipids remains the least understood. Our study revealed that molecular functions related to Stearoyl-CoA Desaturase (SCD), the rate limiting enzyme in monounsaturated fatty acid synthesis were specifically altered in the hippocampus of 3xTg-AD (a model of early-onset AD). Remarkably, infusion of an SCD inhibitor (SCDi) reversed 40% of altered immune and synapse genes, rescue dendritic spine number and structure, recovered activity-associated immediate-early gene expression and restored learning and memory in 3xTg-AD mice. In addition, we employed single cell RNA sequencing to characterize the cellular landscape of microglia subpopulations within the 3xTg hippocampus and uncovered that SCDi reversed microglial activation and polarization. Together, we show that a single lipid enzyme, SCD, impinges on the core features of AD.
Project description:Methylglyoxal (MG) is a reactive alpha-dicarbonyl by-product of glycolysis. Several bio-defense systems to detoxify the highly toxic MG are equipped in our body, including an enzymatic system by glyoxalase (GLO) 1 and GLO2 and a scavenge system by vitamin B6 (VB6). We have reported that some population of patients with schizophrenia shows impairment of the MG detoxification systems. Although we have evidences showing a link between impairment of MG detoxification systems and development of schizophrenia, the molecular mechanism to connect them remains poorly understood. Here, we generated a novel mouse model for MG detoxification deficits by feeding Glo1 knockout mice with VB6-lacking diets (KO/VB6(-)), and evaluate effects of impaired MG detoxification systems on brain function. KO/VB6(-) mice showed the accumulation of MG in the prefrontal cortex (PFC), hippocampus, and striatum, and displayed schizophrenia-like behavioral deficits, such as social deficits, cognitive impairment, a sensorimotor deficit in the prepulse inhibition test. Furthermore, we found aberrant gene expression related to mitochondria function in the PFC of the KO/VB6(-) mice by RNA-seq and weighted gene correlation network analysis (WGCNA). Finally, we actually demonstrated respiratory deficits in mitochondria isolated from the PFC of KO/VB6(-) mice. These findings suggest that MG detoxification deficits might cause schizophrenia-like behavioral deficits via mitochondrial dysfunction in the PFC.
Project description:Autism spectrum disorder (ASD) is a neurodevelopmental condition of unknown mechanism. Synaptic pathology is a core feature, but the key molecular regulators are unclear. The brain's major apolipoprotein APOE transports lipids including S1P to regulate neuronal function; however, the role of the APOE/S1P axis in ASD is unknown. Here, we found that serum APOE and S1P were elevated in children with ASD. In the BTBR mouse hippocampus, both were also elevated, with abnormal APOE aggregation on neurons. To test causality, we developed a brain-targeted nanomicelle (MAN@SKI II) that inhibits hippocampal S1P. MAN@SKI II lowered APOE/S1P levels, reactivated the PI3K/Akt/mTOR pathway, repaired synaptic ultrastructure, and improved social and cognitive behaviors in BTBR mice. Together, these findings indicate that the APOE/S1P axis plays a regulatory role in hippocampal synaptic pathology and behavioral deficits in ASD, suggesting a potential mechanistic target for therapeutic intervention.
Project description:The human 16p11.2 gene locus is a hot spot for copy number variations, which predispose carriers to a range of neuropsychiatric phenotypes. Microduplications of 16p11.2 are associated with autism spectrum disorder (ASD), intellectual disability (ID), and schizophrenia (SZ). Despite the debilitating nature of 16p11.2 duplications, the underlying molecular mechanisms remain poorly understood. Here we performed a comprehensive behavioral characterization of 16p11.2 duplication mice (16p11.2dp/+) and identified social and cognitive deficits reminiscent of ASD and ID phenotypes. 16p11.2dp/+ mice did not exhibit the SZ-related sensorimotor gating deficits, psychostimulant-induced hypersensitivity, or motor impairment. Electrophysiological recordings of 16p11.2dp/+ mice found deficient GABAergic synaptic transmission and elevated neuronal excitability in the prefrontal cortex (PFC), a brain region critical for social and cognitive functions. RNA-sequencing identified genome-wide transcriptional aberrance in the PFC of 16p11.2dp/+ mice, including downregulation of the GABA synapse regulator Npas4. Restoring Npas4 expression in PFC of 16p11.2dp/+ mice ameliorated the social and cognitive deficits and reversed GABAergic synaptic impairment and neuronal hyperexcitability. These findings suggest that prefrontal cortical GABAergic synaptic circuitry and Npas4 are strongly implicated in 16p11.2 duplication pathology, and may represent potential targets for therapeutic intervention in ASD.