Signaling Deficits Research Articles

The Chrysanthemum Phenotype of Idiopathic Multifocal Choroiditis.

To describe the clinical characteristics and multimodal imaging (MMI) features of a distinctive subtype of active idiopathic multifocal choroiditis (iMFC) lesions with grey-yellow chorioretinal lesions surrounded by smaller satellite dots, a presentation referred to as "chrysanthemum lesions". Retrospective, observational, multi-center case series of eyes with active iMFC and chrysanthemum lesions. Multimodal imaging features were reviewed and presented. Twenty-five eyes from 20 patients (12 women and 8 men), with a mean age of 35.8±17.0 years (range, 7 - 78 years) were included. Chrysanthemum lesions were equally located in the macula (48.0%) or the mid/far-periphery (52.0%). The number of lesions per eye varied from 1 (16.0%) to more than 20 (56.0%). On optical coherence tomography (OCT), chrysanthemum lesions showed typical features of iMFC, including subretinal hyperreflective material splitting the retinal pigment epithelium/Bruch's membrane (RPE/BrM). Chrysanthemum lesions were hypoautofluorescent on fundus autofluorescence imaging, hyperfluorescent on fluorescein angiography, hypofluorescent on indocyanine green angiography, and associated with choriocapillaris flow signal deficit on OCT-angiography. Active iMFC may present with findings resembling chrysanthemum lesions. The distinctive lesion morphology on ophthalmoscopic examination, the high number of lesions, and the high prevalence of exclusive mid- and far-peripheral involvement may represent a distinctive phenotype of iMFC.

Disruptive lysosomal-metabolic signaling and neurodevelopmental deficits that precede Purkinje cell loss in a mouse model of Niemann-Pick Type-C disease

Purkinje cell (PC) loss occurs at an early age in patients and animal models of Niemann-Pick Type C (NPC), a lysosomal storage disease caused by mutations in the Npc1 or Npc2 genes. Although degeneration of PCs occurs early in NPC, little is known about how NPC1 deficiency affects the postnatal development of PCs. Using the Npc1nmf164 mouse model, we found that NPC1 deficiency significantly affected the postnatal development of PC dendrites and synapses. The developing dendrites of Npc1nmf164 PCs were significantly deficient in mitochondria and lysosomes. Furthermore, anabolic (mTORC1) and catabolic (TFEB) signaling pathways were not only perturbed but simultaneously activated in NPC1-deficient PCs, suggesting a loss of metabolic balance. We also found that mice with conditional heterozygous deletion of the Phosphatase and Tensin Homolog Deleted on Chromosome 10 gene (Pten-cHet), an inhibitor of mTORC1, showed similar early dendritic alterations in PCs to those found in Npc1-deficient mice. However, in contrast to Npc1nmf164 mice, Pten-cHet mice exhibited the overactivation of the mTORC1 pathway but with a strong inhibition of TFEB signaling, along with no dendritic mitochondrial reductions by the end of their postnatal development. Our data suggest that disruption of the lysosomal-metabolic signaling in PCs causes dendritic and synaptic developmental deficits that precede and promote their early degeneration in NPC.

Abstract 3190: ALA-CART induces global transcriptional changes leading to enhanced potency and persistence of CAR T cells against both lymphoid and myeloid acute leukemias

Abstract Chimeric antigen receptor (CAR) T cell therapy has revolutionized cancer treatment, demonstrating clinical success in B-cell malignancies that are refractory to standard therapies. Relapses after CAR therapy has demonstrated the limitations of current CAR T cell therapies to target antigen-low tumors and induce consistent persistence. Furthermore, the success of CAR T cell therapy in B-lineage malignancies has not yet been translated to acute myeloid leukemia (AML). The targeting of myeloid-restricted antigens, such as CD33, with standard 2nd generation CAR T cells has not yielded similar clinical responses as ALL. Therefore, we hypothesize that novel CAR T cell strategies will be required to improve responses in non-B cell malignancies. We identified that CAR T cells inefficiently activate the scaffolding protein LAT in response to low levels of antigen, leading to diminished efficacy. We designed a bicistronic construct consisting of a clinically active 2nd generation CD22-BBz CAR along with a novel Adjunctive LAT Activating CAR incorporating the intracellular signaling domain of LAT (ALA-CART) to overcome this deficiency of signaling in CAR T cells. In xenograft models, 22ALA-CART cells completely eradicated CD22-low leukemia, which is not responsive to standard CD22-BBz CAR T cells. We have extended these findings to CD19-directed ALA-CART cells, which eradicate CD19-low leukemia that is otherwise resistant to standard CD19-BBz CAR T cells. To understand how ALA-CART improves responses to antigen-low leukemia, we evaluated the in vivo potency of ALA-CART relative to 2nd generation CARs and found ALA-CART cells could eradicate ALL in xenograft models at lower doses than standard CAR T cells. RNA-Seq analysis demonstrated global differences in ALA-CART cells in the resting state reflecting a less differentiated state, which corresponded to an enrichment of T stem cell memory cells and enhanced in vivo persistence. Stimulation through the ALA-CART receptor led to widespread changes in transcription factor activity in T cells which were distinct from standard CAR activation, particularly inducing significantly lower interferon response factor activity which has been associated with CAR T cell failure in patients. As strategies targeting myeloid lineage-restricted antigens with 2nd generation CAR T cells have not yet produced the clinical success seen with ALL-directed CAR therapy, we tested whether the ALA-CART platform could improve the activity of CD33-directed CAR T cells. CD33 ALA-CART cells demonstrated improved in vivo potency and exhibited enhanced memory potential like our results with ALL-directed ALA-CART. Thus, through the reversal of signaling deficits intrinsic to 2nd generation CARs, the ALA-CART platform improves the potency and persistence of CAR T cell therapy against both lymphoid and myeloid acute leukemias. Citation Format: Catherine Danis, Lillie Leach, Christopher Ebmeier, Amanda Novak, Etienne Danis, M. Eric Kohler. ALA-CART induces global transcriptional changes leading to enhanced potency and persistence of CAR T cells against both lymphoid and myeloid acute leukemias [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3190.

Glutamate shall not pass: a mechanistic role for astrocytic O-GlcNAc transferase in stress and depression.

Major depressive disorder, characterized by aberrant glutamatergic signaling in the prefrontal cortex (PFC), is a leading cause of disability worldwide. Depression is highly comorbid with metabolic disorders, but a mechanistic link is elusive. In this issue of the JCI, Fan and coauthors report that elevated posttranslational modification with the glucose metabolite N-acetylglucosamine (GlcNAc) by O-GlcNAc transferase (OGT) contributed to stress-induced establishment of depression-like behaviors in mice. This effect was specific to medial PFC (mPFC) astrocytes, with glutamate transporter-1 (GLT-1) identified as an OGT target. Specifically, O-GlcNAcylation of GLT-1 resulted in diminished glutamate clearance from excitatory synapses. Further, astrocytic OGT knockdown restored stress-induced deficits in glutamatergic signaling, promoting resilience. These findings provide a mechanistic link between metabolism and depression and have relevance for antidepressant targets.

Overexpression screen of chromosome 21 genes reveals modulators of Sonic hedgehog signaling relevant to Down syndrome.

Trisomy 21 and mutations in the Sonic hedgehog (SHH) signaling pathway cause overlapping and pleiotropic phenotypes including cerebellar hypoplasia, craniofacial abnormalities, congenital heart defects and Hirschsprung disease. Trisomic cells derived from individuals with Down syndrome possess deficits in SHH signaling, suggesting that overexpression of human chromosome 21 genes may contribute to SHH-associated phenotypes by disrupting normal SHH signaling during development. However, chromosome 21 does not encode any known components of the canonical SHH pathway. Here, we sought to identify chromosome 21 genes that modulate SHH signaling by overexpressing 163 chromosome 21 cDNAs in a series of SHH-responsive mouse cell lines. We confirmed overexpression of trisomic candidate genes using RNA sequencing in the cerebella of Ts65Dn and TcMAC21 mice, model systems for Down syndrome. Our findings indicate that some human chromosome 21 genes, including DYRK1A, upregulate SHH signaling, whereas others, such as HMGN1, inhibit SHH signaling. Individual overexpression of four genes (B3GALT5, ETS2, HMGN1 and MIS18A) inhibits the SHH-dependent proliferation of primary granule cell precursors. Our study prioritizes dosage-sensitive chromosome 21 genes for future mechanistic studies. Identification of the genes that modulate SHH signaling may suggest new therapeutic avenues for ameliorating Down syndrome phenotypes.

Efficacy and Safety of Iclepertin (BI 425809) in Patients With Schizophrenia: CONNEX, A Phase III Randomized Controlled Trial Program

AbstractIntroductionCognitive impairment is a major determinant of poor functional outcome in schizophrenia and there are currently no available pharmacotherapies. Deficits in glutamatergic signaling play a key role in the neuropathology of cognitive symptoms. Iclepertin (BI 425809), an inhibitor of glycine transporter-1, enhances glutamatergic signaling by increasing synaptic levels of the N-methyl-D-aspartate receptor co-agonist, glycine. A 12-week, Phase II trial (NCT02832037) in 509 patients with schizophrenia demonstrated that iclepertin was well tolerated and significantly improved cognition. The Phase III CONNEX program aims to confirm the efficacy, safety, and tolerability of iclepertin in improving cognition and functioning in a larger cohort of patients.MethodsCONNEX consists of three replicate randomized, double-blind, placebo-controlled parallel-group trials in patients with schizophrenia (NCT04846868, NCT04846881, NCT04860830) currently stable on antipsychotic treatment. Each trial aims to recruit ~586 patients, 18–50 years old, treated with 1–2 antipsychotic medications (≥12 weeks on current drug; ≥35 days on current dose prior to treatment), who have functional impairment in day-to-day activities, and interact ≥1 hour per week with a designated study partner. Patients with cognitive impairment due to developmental, neurological, or other disorders, or receiving cognitive remediation therapy within 12 weeks prior to screening, will be excluded. Patients will be recruited from multiple centers across 32 countries in Asia, North and South America, and Europe, and randomized 1:1 to receive either oral iclepertin 10 mg (n=293), or placebo (n=293) once daily over 26 weeks. The primary efficacy endpoint is change from baseline (CfB) in the MATRICS Consensus Cognitive Battery overall composite T-score. Key secondary efficacy endpoints are CfB in Schizophrenia Cognition Rating Scale total score and CfB in the adjusted total time in the Virtual Reality Functional Capacity Assessment Tool. Long-term safety and tolerability data will be collected in an open-label safety extension study (CONNEX-X).ResultsThe studies are currently recruiting (first patients enrolled Aug–Sept 2021), with completion expected in Q2 2024. Here we present an overview of the current study status, including any information relating to screening failures, and the experience of collecting these data as part of a large multi-country, multi-center study.ConclusionTo date, most large, industry-sponsored studies testing various compounds to address cognitive function have failed to show proof-of-clinical concept. Demonstration of efficacy of iclepertin in improving cognition in this Phase III program would provide important insight into the role of glutamate in cognitive symptoms that may also have relevance for other cognitive disorders. Iclepertin may represent the first efficacious medication for cognitive impairment associated with schizophrenia.FundingBoehringer Ingelheim International GmbH (1346-0011, NCT04846868; 1346-0012, NCT04846881; 1346-0013, NCT04860830)

Hippocampal dentate gyri proteomics reveals Wnt signaling involvement in the behavioral impairment in the THRSP-overexpressing ADHD mouse model

Children with attention-deficit/hyperactivity disorder (ADHD) often struggle with impaired executive function, temporal processing, and visuospatial memory, hallmarks of the predominantly inattentive presentation (ADHD-PI), subserved by the hippocampus. However, the specific genes/proteins involved and how they shape hippocampal structures to influence ADHD behavior remain poorly understood. As an exploratory tool, hippocampal dentate gyri tissues from thyroid hormone-responsive protein overexpressing (THRSP OE) mice with defining characteristics of ADHD-PI were utilized in proteomics. Integrated proteomics and network analysis revealed an altered protein network involved in Wnt signaling. Compared with THRSP knockout (KO) mice, THRSP OE mice showed impaired attention and memory, accompanied by dysregulated Wnt signaling affecting hippocampal dentate gyrus cell proliferation and expression of markers for neural stem cell (NSC) activity. Also, combined exposure to an enriched environment and treadmill exercise could improve behavioral deficits in THRSP OE mice and Wnt signaling and NSC activity. These findings show new markers specific to the ADHD-PI presentation, converging with the ancient and evolutionary Wnt signaling pathways crucial for cell fate determination, migration, polarity, and neural patterning during neurodevelopment. These findings from THRSP OE mice support the role of Wnt signaling in neurological disorders, particularly ADHD-PI presentation.

Xanomeline restores endogenous nicotinic acetylcholine receptor signaling in mouse prefrontal cortex

Cholinergic synapses in prefrontal cortex are vital for attention, but this modulatory system undergoes substantial pre- and post-synaptic alterations during adulthood. To examine the integrated impact of these changes, we optophysiologically probe cholinergic synapses ex vivo, revealing a clear decline in neurotransmission in middle adulthood. Pharmacological dissection of synaptic components reveals a selective reduction in postsynaptic nicotinic receptor currents. Other components of cholinergic synapses appear stable, by contrast, including acetylcholine autoinhibition, metabolism, and excitation of postsynaptic muscarinic receptors. Pursuing strategies to strengthen cholinergic neurotransmission, we find that positive allosteric modulation of nicotinic receptors with NS9283 is effective in young adults but wanes with age. To boost nicotinic receptor availability, we harness the second messenger pathways of the preserved excitatory muscarinic receptors with xanomeline. This muscarinic agonist and cognitive-enhancer restores nicotinic signaling in older mice significantly, in a muscarinic- and PKC-dependent manner. The rescued nicotinic component regains youthful sensitivity to allosteric enhancement: treatment with xanomeline and NS9283 restores cholinergic synapses in older mice to the strength, speed, and receptor mechanism of young adults. Our results reveal a new and efficient strategy to rescue age-related nicotinic signaling deficits, demonstrating a novel pathway for xanomeline to restore cognitively-essential endogenous cholinergic neurotransmission.

Testing Model Predictions of Depth of Air-Shower Maximum and Signals in Surface Detectors using Hybrid Data of the Pierre Auger Observatory

We present a method for testing the predictions of hadronic interaction models and improving their consistency with observed two-dimensional distributions of the depth of shower maximum, X max, and signal at the ground level as a function of zenith angle. The method relies on the assumption that the mass composition is the same at all zenith angles, while the atmospheric shower development and attenuation depend on composition in a correlated way. In the present work, for each of the three leading LHC-tuned hadronic interaction models, we allow a global shift ∆ X max of the predicted shower maximum, which is the same for every mass and energy, and a rescaling R Had of the hadronic component at the ground level which is constant with the zenith angle. We apply the analysis to 2297 events reconstructed with both the fluorescence and surface detectors of the Pierre Auger Observatory with energies 1018.5−19.0 eV and zenith angles below 60°. Given the modeling assumptions made in this analysis, the best fit reaches its optimum value when shifting the X max predictions of hadronic interaction models to deeper values and increasing the hadronic signal. This change in the predicted X max scale alleviates the previously identified model deficit in the hadronic signal (commonly called the muon puzzle) but does not fully remove it. Because of the size of the adjustments ∆ X max and R Had and the large number of events in the sample, the statistical significance of need for these adjustments is large, greater than 5σstat, even for the combination of the systematic experimental shifts within 1σsys that are the most favorable for the models.

Faded neural projection from the posterior bed nucleus of the stria terminalis to the lateral habenula contributes to social signaling deficit in male BTBR mice as a mouse model of autism

BTBR T+ Itpr3tf/J (BTBR) mice display several behavioral characteristics, including social deficits resembling the core symptoms of human autism. Atypical social behaviors include sequential processes of assembled cognitive-behavior components, such as recognition, investigatory assessment, and signaling response. This study aimed to elucidate the neural circuits responsible for the regulation of the social signaling response, as shown by scent marking behavior in male mice. We first assessed the recognition and investigatory patterns of male BTBR mice compared to those of C57BL/6 J (B6) mice. Next, we examined their scent-marking behavior as innate social signaling responses adjusted to a confronted feature of social stimuli and situations, along with the expression of c-Fos as a marker of neuronal activity in selected brain areas involved in the regulation of social behavior. The function of the targeted brain area was confirmed by chemogenetic manipulation. We also examined the social peptides, oxytocin and vasopressin neurons of the major brain regions that are associated with the regulation of social behavior. Our data indicate that male BTBR mice are less responsive to the presentation of social stimuli and the expression of social signaling responses, which is paralleled by blunted c-Fos responsivity and vasopressin neurons morphological changes in selected brain areas, including the posterior bed nucleus of the stria terminalis (pBnST) and lateral habenula (LHb) in BTBR mice. Further investigation of LHb function revealed that chemogenetic inhibition and activation of LHb activity can induce a change in scent marking responses in both B6 and BTBR mice. Our elucidation of the downstream LHb circuits controlling scent marking behavior indicates intact function in BTBR mice. The altered morphological characteristics of oxytocin neurons in the paraventricular nucleus of the hypothalamus and vasopressin-positive neurons and axonal projections in the pBnST and LHb appear to underlie the dysfunction of scent marking responses in BTBR mice.(300/300 words)

Depressed Protein Synthesis and Anabolic Signaling Potentiate ACL Tear–Resultant Quadriceps Atrophy

Background: Anterior cruciate ligament (ACL) tear (ACLT) leads to protracted quadriceps muscle atrophy. Protein turnover largely dictates muscle size and is highly responsive to injury and loading. Regulation of quadriceps molecular protein synthetic machinery after ACLT has largely been unexplored, limiting development of targeted therapies. Purpose: To define the effect of ACLT on (1) the activation of protein synthetic and catabolic signaling within quadriceps biopsy specimens from human participants and (2) the time course of alterations to protein synthesis and its molecular regulation in a mouse ACL injury model. Study Design: Descriptive laboratory study. Methods: Muscle biopsy specimens were obtained from the ACL-injured and noninjured vastus lateralis of young adult humans after an overnight fast (N = 21; mean ± SD, 19 ± 5 years). Mice had their limbs assigned to ACLT or control, and whole quadriceps were collected 6 hours or 1, 3, or 7 days after injury with puromycin injected before tissue collection for assessment of relative protein synthesis. Muscle fiber size and expression and phosphorylation of protein anabolic and catabolic signaling proteins were assessed at the protein and transcript levels (RNA sequencing). Results: Human quadriceps showed reduced phosphorylation of ribosomal protein S6 (–41%) in the ACL-injured limb (P = .008), in addition to elevated phosphorylation of eukaryotic initiation factor 2α (+98%; P = .006), indicative of depressed protein anabolic signaling in the injured limb. No differences in E3 ubiquitin ligase expression were noted. Protein synthesis was lower at 1 day (P = .01 vs control limb) and 3 days (P = .002 vs control limb) after ACLT in mice. Pathway analyses revealed shared molecular alterations between human and mouse quadriceps after ACLT. Conclusion: (1) Global protein synthesis and anabolic signaling deficits occur in the quadriceps in response to ACL injury, without notable changes in measured markers of muscle protein catabolism. (2) Importantly, these deficits occur before the onset of significant atrophy, underscoring the need for early intervention. Clinical Relevance: These findings suggest that blunted protein anabolism as opposed to increased catabolism likely mediates quadriceps atrophy after ACL injury. Thus, future interventions should aim to restore muscle protein anabolism rapidly after ACLT.

Multi-omic profiling reveals the ataxia protein sacsin is required for integrin trafficking and synaptic organization.

Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is a childhood-onset cerebellar ataxia caused by mutations in SACS, which encodes the protein sacsin. Cellular ARSACS phenotypes include mitochondrial dysfunction, intermediate filament disorganization, and progressive death of cerebellar Purkinje neurons. It is unclear why the loss of sacsin causes these deficits or why they manifest as cerebellar ataxia. Here, we perform multi-omic profiling in sacsin knockout (KO) cells and identify alterations in microtubule dynamics and mislocalization of focal adhesion (FA) proteins, including multiple integrins. Deficits in FA structure, signaling, and function can be rescued by targeting PTEN, a negative regulator of FA signaling. ARSACS mice possess mislocalization of ITGA1 in Purkinje neurons and synaptic disorganization in the deep cerebellar nucleus (DCN). The sacsin interactome reveals that sacsin regulates interactions between cytoskeletal and synaptic adhesion proteins. Our findings suggest that disrupted trafficking of synaptic adhesion proteins is a causal molecular deficit in ARSACS.

Ral GTPases are critical regulators of spinal cord myelination and homeostasis.

Efficient myelination supports nerve conduction and axonal health throughout life. In the central nervous system, oligodendrocytes (OLs) carry out this demanding anabolic duty in part through biosynthetic pathways controlled by mTOR. We identify Ral GTPases as critical regulators of mouse spinal cord myelination and myelin maintenance. Ablation of Ral GTPases (RalA, RalB) in OL-lineage cells impairs timely onset and radial growth of developmental myelination, accompanied by increased endosomal/lysosomal abundance. Further examinations, including transcriptomic analyses of Ral-deficient OLs, were consistent with mTORC1-related deficits. However, deletion of the mTOR signaling-repressor Pten in Ral-deficient OL-lineage cells is unable to rescue mTORC1 activation or developmental myelination deficiencies. Induced deletion of Ral GTPases in OLs of adult mice results in late-onset myelination defects and tissue degeneration. Together, our data indicate critical roles for Ral GTPases to promote developmental spinal cord myelination, to ensure accurate mTORC1 signaling, and to protect the healthy state of myelin-axon units over time.

Differences in H3K4me3 and chromatin accessibility contribute to altered T-cell receptor signaling in neonatal naïve CD4 T cells.

Neonatal CD4+ T cells have reduced or delayed T-cell receptor (TCR) signaling responses compared with adult cells, but the mechanisms underlying this are poorly understood. This study tested the hypothesis that human neonatal naïve CD4+ TCR signaling and activation deficits are related to differences in H3K4me3 patterning and chromatin accessibility. Following initiation of TCR signaling using anti-CD3/anti-CD28 beads, adult naïve CD4+ T cells demonstrated increased CD69, phospho-CD3ε and interleukin (IL)-2, tumor necrosis factor-α (TNF-α), interferon-γ and IL-17A compared with neonatal cells. By contrast, following TCR-independent activation using phorbol myristate acetate (PMA)/ionomycin, neonatal cells demonstrated increased expression of CD69, IL-2 and TNF-α and equivalent phospho-ERK compared with adult cells. H3K4me3 chromatin immunoprecipitation-sequencing (ChIP-seq) and assay for transposase-accessible chromatin with high-throughput sequencing (ATAC-seq) were performed on separate cohorts of naïve CD4+ T cells from term neonates and adults, and RNA-seq data from neonatal and adult naïve CD4+ T cells were obtained from the Blueprint Consortium. Adult cells demonstrated overall increased chromatin accessibility and a higher proportion of H3K4me3 sites associated with open chromatin and active gene transcription compared with neonatal cells. Adult cells demonstrated increased mRNA expression of the TCR-associated genes FYN, ITK, CD4, LCK and LAT, which was associated with increased H3K4me3 at the FYN and ITK gene loci and increased chromatin accessibility at the CD4, LCK and LAT loci. These findings indicate that neonatal TCR-dependent defects in activation are epigenetically regulated and provide a potentially targetable mechanism to enhance neonatal CD4+ T-cell responses.

Abstract 3607: A novel adjunctive LAT-activating CAR T (ALA-CART) cell platform demonstrates enhanced antigen sensitivity and eradication of antigen-low leukemia

Abstract CAR T cells have demonstrated clinical success in malignancies that are refractory to standard therapies; however, preclinical and clinical studies have demonstrated that CAR T cell efficacy is greatly reduced in settings of low levels of target antigen. This was exemplified in a clinical trial of CD22-directed CAR T cells where despite inducing complete remissions in >70% of patients, post-CAR relapses occurred in the majority of patients, driven by decreased expression of CD22 below the threshold required for adequate CAR T cell activation. To address this limitation of CAR T cells, we investigated the mechanism underlying suboptimal CAR responses to low levels of antigen. Using a SILAC/mass spectrometry approach, we performed global phosphoproteomics to examine CAR T cell signal transduction in response to high- and low-levels of CD22 antigen. Low levels of CD22 antigen resulted in decreased utilization of several canonical T cell signaling pathways in CAR T cells. We hypothesized that LAT, a scaffolding protein integral to the T cell signalosome, was inefficiently utilized in response to low levels of antigen. Indeed, while signaling events proximal to LAT, such as Zap70, were unaffected by CD22 antigen density, phosphorylation of LAT at multiple activating residues decreased in response to stimulation with CD22-low leukemia cells. To overcome the inefficient LAT activation by low levels of antigen, we designed a bicistronic construct consisting of a clinically active 2nd generation CD22-BBz CAR along with a novel Adjunctive LAT Activating CAR incorporating the intracellular signaling domain of LAT (ALA-CART). ALA-CART cells expressed both CARs on the surface and demonstrated enhanced phosphorylation of LAT and PLCγ in response to CD22-low leukemia cells. In xenograft models, ALA-CART cells completely eradicated CD22-low leukemia, significantly extending survival of mice in comparison to the standard CD22-BBz CAR which only modestly slowed leukemia progression. Additionally, in mice engrafted with leukemia expressing WT-levels of CD22, we found the persistence of ALA-CART cell was significantly enhanced relative to standard CD22-BBz CAR T cells. Thus, by identifying deficits in CAR signaling, we rationally designed the ALA-CART platform to target antigen-low cells, overcoming a mechanism of resistance to standard CAR therapies with the potential to improve outcomes of patients receiving CAR therapies. Citation Format: Catherine Pham-Danis, Lillie Leach, Christopher Ebmeier, M. Eric Kohler. A novel adjunctive LAT-activating CAR T (ALA-CART) cell platform demonstrates enhanced antigen sensitivity and eradication of antigen-low leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3607.

Symptomatic and neurotrophic effects of GABAA receptor positive allosteric modulation in a mouse model of chronic stress.

Chronic stress is a risk factor for Major Depressive Disorder (MDD), and in rodents, it recapitulates human behavioral, cellular and molecular changes. In MDD and after chronic stress, neuronal dysfunctions and deficits in GABAergic signaling are observed and responsible for symptom severity. GABA signals predominantly through GABAA receptors (GABAA-R) composed of various subunit types that relate to downstream outcomes. Activity at α2-GABAA-Rs contributes to anxiolytic properties, α5-GABAA-Rs to cognitive functions, and α1-GABAA-Rs to sedation. Therefore, a therapy aiming at increasing α2- and α5-GABAA-Rs activity, but devoid of α1-GABAA-R activity, has potential to address several symptomologies of depression while avoiding side-effects. This study investigated the activity profiles and behavioral efficacy of two enantiomers of each other (GL-II-73 and GL-I-54), separately and as a racemic mixture (GL-RM), and potential disease-modifying effects on neuronal morphology. Results confirm GL-I-54 and GL-II-73 exert positive allosteric modulation at the α2-, α3-, α5-GABAA-Rs and α5-containing GABAA-Rs, respectively, and separately reduces immobility in the forced swim test and improves stress-induced spatial working memory deficits. Using unpredictable chronic mild stress (UCMS), we show that acute and chronic administration of GL-RM provide pro-cognitive effects, with mild efficacy on mood symptoms, although at lower doses avoiding sedation. Morphology studies showed reversal of spine density loss caused by UCMS after chronic GL-RM treatment at apical and basal dendrites of the PFC and CA1. Together, these results support using a racemic mixture with combined α2-, α3-, α5-GABAA-R profile to reverse chronic stress-induced mood symptoms, cognitive deficits, and with anti-stress neurotrophic effects.

Correction to: Exercise Rehabilitation and/or Astragaloside Attenuate Amyloid-beta Pathology by Reversing BDNF/TrkB Signaling Deficits and Mitochondrial Dysfunction

Correction to: Exercise Rehabilitation and/or Astragaloside Attenuate Amyloid-beta Pathology by Reversing BDNF/TrkB Signaling Deficits and Mitochondrial Dysfunction

Generation of an Adeno‐Associated Viral Model of Murine Obesity

Cardiovascular disease (CVD) is a major contributor to US morbidity and mortality; significantly increasing chronic disabilities and shortening life expectancy. Obesity is a major driver of CVD and the rapid rise in the numbers of obese individuals portends an alarming societal burden. The etiology of CVD in obesity is incompletely understood and potential interventions to break the links between weight gain and vascular disease remain a critical barrier to treatment. Modeling complex disorders such as obesity in mice is an imperfect science but mouse models lacking leptin (ob/ob) or leptin receptors (db/db) mimic key aspects of human disease such as hyperphagia, overt obesity and vascular dysfunction. Limitations of these models include deficits in leptin signaling (not widely seen in humans), infertility which is a barrier to making compound genetic models and little to no temporal control of onset. To address these concerns, we hypothesized that delivery of AgRP, an orexigenic signaling molecule, to the brain of a C57BL6 mouse via a brain‐specific AAV would precipitate hyperphagia and obesity and recapitulate the vascular dysfunction exhibited by other hyperphagic models. Administration of this AAV elicits tightly restricted expression of AgRP in the brain and a significant (p=0.002) hyperphagic response on a standard chow diet. This leads to subsequent robust weight gain to a final weight of 63.1±2.1g, comparable to that of the db/db model. Pressure myography of mesenteric microvessels from lean control and obese AgRP AAV mice showed significant (p<0.001) impairment in endothelial dependent relaxation in the vessels from obese animals. Overall our findings with this model recapitulate the obesity and vascular dysfunction seen in other severely obese mouse models while providing increased flexibility and temporal control.

ON than OFF pathway disruption leads to greater deficits in visual function and retinal dopamine signaling

The visual system uses ON and OFF pathways to signal luminance increments and decrements. Increasing evidence suggests that ON and OFF pathways have different signaling properties and serve specialized visual functions. However, it is still unclear the contribution of ON and OFF pathways to visual behavior. Therefore, we examined the effects on optomotor response and the retinal dopamine system in nob mice with ON pathway dysfunction and Vsx1−/− mice with partial OFF pathway dysfunction. Spatial frequency and contrast sensitivity thresholds were determined, and values were compared to age-matched wild-type controls. Retinas were collected immediately after visual testing to measure levels of dopamine and its metabolite, DOPAC. At 4 weeks of age, we found that nob mice had significantly reduced spatial frequency (19%) and contrast sensitivity (60%) thresholds compared to wild-type mice. Vsx1−/− mice also exhibited reductions in optomotor responses (3% in spatial frequency; 18% in contrast sensitivity) at 4 weeks, although these changes were significantly smaller than those found in nob mice. Furthermore, nob mice had significantly lower DOPAC levels (53%) and dopamine turnover (41%) compared to controls while Vsx1−/− mice displayed a transient increase in DOPAC levels at 4 weeks of age (55%). Our results show that dysfunction of ON pathways leads to reductions in contrast sensitivity, spatial frequency threshold, and retinal dopamine turnover whereas partial loss of the OFF pathway has minimal effect. We conclude that ON pathways play a critical role in visual reflexes and retinal dopamine signaling, highlighting a potential association for future investigations.

Exercise Rehabilitation and/or Astragaloside Attenuate Amyloid-beta Pathology by Reversing BDNF/TrkB Signaling Deficits and Mitochondrial Dysfunction.

We aim to investigate the mechanisms underlying the beneficial effects of exercise rehabilitation (ER) and/or astragaloside (AST) in counteracting amyloid-beta (Aβ) pathology. Aβ oligomers were microinjected into the bilateral ventricles to induce Aβ neuropathology in rats. Neurobehavioral functions were evaluated. Cortical and hippocampal expressions of both BDNF/TrkB and cathepsin D were determined by the western blotting method. The rat primary cultured cortical neurons were incubated with BDNF and/or AST and ANA12 followed by exposure to aggregated Aβ for 24h. In vivo results showed that ER and/or AST reversed neurobehavioral disorders, downregulation of cortical and hippocampal expression of both BDNF/TrkB and cathepsin D, neural pathology, Aβ accumulation, and altered microglial polarization caused by Aβ. In vitro studies also confirmed that topical application of BDNF and/or AST reversed the Aβ-induced cytotoxicity, apoptosis, mitochondrial distress, and synaptotoxicity and decreased expression of p-TrkB, p-Akt, p-GSK3β, and β-catenin in rat cortical neurons. The beneficial effects of combined ER (or BDNF) and AST therapy in vivo and in vitro were superior to ER (or BDNF) or AST alone. Furthermore, we observed that any gains from ER (or BDNF) and/or AST could be significantly eliminated by ANA-12, a potent BDNF/TrkB antagonist. These results indicate that whereas ER (or BDNF) and/or AST attenuate Aβ pathology by reversing BDNF/TrkB signaling deficits and mitochondrial dysfunction, combining these two potentiates each other's therapeutic effects. In particular, AST can be an alternative therapy to replace ER.