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Triosephosphate isomerase deficiency (TPI Df) is a rare multisystem disorder with severe neuromuscular symptoms which arises exclusively from mutations within the TPI1 gene. Studies of TPI Df have been limited due to the absence of mammalian disease models and difficulties obtaining patient samples. Recently, we developed a novel murine model of TPI Df which models the most common disease-causing mutation in humans, TPI1E105D. Using our model in the present study, the underlying pathogenesis of neuromuscular symptoms has been elucidated. This is the first report detailing studies of neuromuscular pathology within a murine model of TPI Df. We identified several contributors to neuromuscular symptoms, including neurodegeneration in the brain, alterations in neurotransmission at the neuromuscular junction, and reduced muscle fiber size. TPI Df mice also exhibited signs of cardiac pathology and displayed a deficit in vascular smooth muscle functionality. Together, these findings provide insight into pathogenesis of the neuromuscular symptoms in TPI Df and can guide the future development of therapeutics. [ABSTRACT FROM AUTHOR]

Toll-like receptor 4 (TLR4) is a critical component of innate immune signaling and has been implicated in alcohol responses in preclinical and clinical models. Members of the Integrative Neuroscience Initiative on Alcoholism (INIA-Neuroimmune) consortium tested the hypothesis that TLR4 mediates excessive ethanol drinking using the following models: (1) Tlr4 knock-out (KO) rats, (2) selective knockdown of Tlr4 mRNA in mouse nucleus accumbens (NAc), and (3) injection of the TLR4 antagonist (+)-naloxone in mice. Lipopolysaccharide (LPS) decreased food/water intake and body weight in ethanol-naive and ethanol-trained wild-type (WT), but not Tlr4 KO rats. There were no consistent genotypic differences in two-bottle choice chronic ethanol intake or operant self-administration in rats before or after dependence. In mice, (+)-naloxone did not decrease drinking-in-the-dark and only modestly inhibited dependence-driven consumption at the highest dose. Tlr4 knockdown in mouse NAc did not decrease drinking in the two-bottle choice continuous or intermittent access tests. However, the latency to ethanol-induced loss of righting reflex increased and the duration decreased in KO versus WT rats. In rat central amygdala neurons, deletion of Tlr4 altered GABAA receptor function, but not GABA release. Although there were no genotype differences in acute ethanol effects before or after chronic intermittent ethanol exposure, genotype differences were observed after LPS exposure. Using different species and sexes, different methods to inhibit TLR4 signaling, and different ethanol consumption tests, our comprehensive studies indicate that TLR4 may play a role in ethanol-induced sedation and GABAA receptor function, but does not regulate excessive drinking directly and would not be an effective therapeutic target.Significance statementToll-like receptor 4 (TLR4) is a key mediator of innate immune signaling and has been implicated in alcohol responses in animal models and human alcoholics. Members of the Integrative Neuroscience Initiative on Alcoholism (INIA-Neuroimmune) consortium participated in the first comprehensive study across multiple laboratories to test the hypothesis that TLR4 regulates excessive alcohol consumption in different species and different models of chronic, dependence-driven, and binge-like drinking. Although TLR4 was not a critical determinant of excessive drinking, it was important in the acute sedative effects of alcohol. Current research efforts are directed at determining which neuroimmune pathways mediate excessive alcohol drinking and these findings will help to prioritize relevant pathways and potential therapeutic targets.

INTRODUCTION: Fundamental questions remain about the key mechanisms that initiate Alzheimer's disease (AD) and the factors that promote its progression. Here we report the successful generation of the first genetically engineered marmosets that carry knock‐in (KI) point mutations in the presenilin 1 (PSEN1) gene that can be studied from birth throughout lifespan. METHODS: CRISPR/Cas9 was used to generate marmosets with C410Y or A426P point mutations in PSEN1. Founders and their germline offspring are comprehensively studied longitudinally using non‐invasive measures including behavior, biomarkers, neuroimaging, and multiomics signatures. RESULTS: Prior to adulthood, increases in plasma amyloid beta were observed in PSEN1 mutation carriers relative to non‐carriers. Analysis of brain revealed alterations in several enzyme–substrate interactions within the gamma secretase complex prior to adulthood. DISCUSSION: Marmosets carrying KI point mutations in PSEN1 provide the opportunity to study the earliest primate‐specific mechanisms that contribute to the molecular and cellular root causes of AD onset and progression. Highlights: We report the successful generation of genetically engineered marmosets harboring knock‐in point mutations in the PSEN1 gene.PSEN1 marmosets and their germline offspring recapitulate the early emergence of AD‐related biomarkers.Studies as early in life as possible in PSEN1 marmosets will enable the identification of primate‐specific mechanisms that drive disease progression. [ABSTRACT FROM AUTHOR]

One of the great strengths of the mouse model is the wide array of genetic tools that have been developed. Striking examples include methods for directed modification of the genome, and for regulated expression or inactivation of genes. Within neuroscience, it is now routine to express reporter genes, neuronal activity indicators, and opsins in specific neuronal types in the mouse. However, there are considerable anatomical, physiological, cognitive, and behavioral differences between the mouse and the human that, in some areas of inquiry, limit the degree to which insights derived from the mouse can be applied to understanding human neurobiology. Several recent advances have now brought into reach the goal of applying these tools to understanding the primate brain. Here we describe these advances, consider their potential to advance our understanding of the human brain and brain disorders, discuss bioethical considerations, and describe what will be needed to move forward.

There is considerable evidence that ethanol (EtOH) potentiates γ-aminobutyric acid type A receptor (GABA(A)R) action, but only GABA(A)Rs containing δ subunits appear sensitive to low millimolar EtOH. The α4 and δ subunits co-assemble into GABA(A)Rs which are relatively highly expressed at extrasynaptic locations in the dentate gyrus where they mediate tonic inhibition. We previously demonstrated reversible- and time-dependent changes in GABA(A)R function and subunit composition in rats after single-dose EtOH intoxication. We concluded that early tolerance to EtOH occurs by over-activation and subsequent internalization of EtOH-sensitive extrasynaptic α4βδ-GABA(A)Rs. Based on this hypothesis, any highly EtOH-sensitive GABA(A)Rs should be subject to internalization following exposure to suitably high EtOH doses. To test this, we studied the GABA(A)Rs in mice with a global deletion of the α4 subunit (KO). The dentate granule cells of these mice exhibited greatly reduced tonic currents and greatly reduced potentiation by acutely applied EtOH, whereas synaptic currents showed heightened sensitivity to low EtOH concentrations. The hippocampus of naive KO mice showed reduced δ subunit protein levels, but increased α2, and γ2 levels compared to wild-type (WT) controls, suggesting at least partial compensation by these subunits in synaptic, highly EtOH-sensitive GABA(A)Rs of KO mice. In WT mice, cross-linking and Western blot analysis at 1 h after an EtOH challenge (3.5 g/kg, i.p.) revealed increased intracellular fraction of the α1, α4, and δ, but not α2, α5, or γ2 subunits. By contrast, we observed significant internalization of α1, α2, δ, and γ2 subunits after a similar EtOH challenge in KO mice. Synaptic currents from naïve KO mice were more sensitive to potentiation by zolpidem (0.3 μM, requiring α1/α2, inactive at α4/5 GABA(A)Rs) than those from naïve WT mice. At 1 h after EtOH, synaptic currents of WT mice were unchanged, whereas those of KO mice were significantly less sensitive to zolpidem, suggesting decreases in functional α1/2βγ GABA(A)Rs. These data further support our hypothesis that EtOH intoxication induces GABA(A)R plasticity via internalization of highly EtOH-sensitive GABA(A)Rs.

Synaptic plasticity in the amygdala is essential for emotional learning. Fear conditioning, for example, depends on changes in excitatory transmission that occur following NMDA receptor activation and AMPA receptor modification in this region. The role of these and other glutamatergic mechanisms have been studied extensively in this circuit while relatively little is known about the contribution of inhibitory transmission. The current experiments addressed this issue by examining the role of the GABA(A) receptor subunit alpha1 in fear learning and plasticity. We first confirmed previous findings that the alpha1 subunit is highly expressed in the lateral nucleus of the amygdala. Consistent with this observation, genetic deletion of this subunit selectively enhanced plasticity in the lateral amygdala and increased auditory fear conditioning. Mice with selective deletion of alpha1 in excitatory cells did not exhibit enhanced learning. Finally, infusion of a alpha1 receptor antagonist into the lateral amygdala selectively impaired auditory fear learning. Together, these results suggest that inhibitory transmission mediated by alpha1-containing GABA(A) receptors plays a critical role in amygdala plasticity and fear learning.

Synaptic plasticity in the amygdala is essential for emotional learning. Fear conditioning, for example, depends on changes in excitatory transmission that occur following NMDA receptor activation and AMPA receptor modification in this region. The role of these and other glutamatergic mechanisms have been studied extensively in this circuit while relatively little is known about the contribution of inhibitory transmission. The current experiments addressed this issue by examining the role of the GABA(A) receptor subunit alpha1 in fear learning and plasticity. We first confirmed previous findings that the alpha1 subunit is highly expressed in the lateral nucleus of the amygdala. Consistent with this observation, genetic deletion of this subunit selectively enhanced plasticity in the lateral amygdala and increased auditory fear conditioning. Mice with selective deletion of alpha1 in excitatory cells did not exhibit enhanced learning. Finally, infusion of a alpha1 receptor antagonist into the lateral amygdala selectively impaired auditory fear learning. Together, these results suggest that inhibitory transmission mediated by alpha1-containing GABA(A) receptors plays a critical role in amygdala plasticity and fear learning.