Preweaning Sensorimotor Deficits and Adolescent Hypersociability in Grin1 Knockdown Mice

Mice with knockdown of the N-methyl-D-aspartate (NMDA) receptor NR1 subunit, encoded by the gene Grin1, have been investigated as a model for the intrinsic NMDA hypofunction hypothesized for schizophrenia. Previous work has shown that adult Grin1 mutant mice have overt deficits in habituation and sensorimotor gating, exaggerated reactivity to environmental stimuli, reduced social approach, and other alterations that reflect behavioral manifestations of schizophrenia. In humans, the emergence of overt symptoms of the disorder typically occurs in adolescence or early adulthood, suggesting a role for aberrant maturation of NMDA receptor signaling in symptom onset. The following study evaluated Grin1 mutant mice for abnormal behavioral phenotypes during the preweaning, adolescent, and adult periods. Measures included open field activity, prepulse inhibition of acoustic startle responses, and social preference in a three-chamber choice task. Mice from the C57BL/6J inbred strain, one of the parental strains for the Grin1 line, were also tested. The results showed that developmental reduction of NMDA receptor function led to significant alterations in behavior during the second and third weeks of life, including exaggerated startle responses and sensorimotor gating deficits on postnatal day 13, and pronounced hypersociability in adolescence. Male Grin1 mutant mice were more susceptible than female mice to the detrimental effects of decreased NMDA signaling. Overall, these findings provide evidence that reduced Grin1 function leads to abnormal phenotypes in the preweaning period, and that deficient NMDA signaling can lead to both overt hypersociability or marked asociality, dependent upon sex and age

Adolescent Binge Alcohol Enhances Early Alzheimer’s Disease Pathology in Adulthood Through Proinflammatory Neuroimmune Activation

Epidemiological studies suggest that heavy alcohol use early in life is associated with increased risk for Alzheimer’s disease (AD). However, mechanisms connecting AD with alcohol use have not been identified. Both heavy alcohol use and AD feature increased proinflammatory signaling. Therefore, we hypothesized that adolescent binge ethanol would increase AD molecular and behavioral pathology in adulthood through proinflammatory signaling. The 3xTg-AD mouse model (APPSwe, tauP301, Psen1tm1Mpm) which features amyloid (Aβ) and tau pathology beginning at 6–12 months underwent adolescent intermittent ethanol (AIE, 5 g/kg/d, i.g., P25-55) with assessment of AD pathologic mediators at P200. A second group of mice received AIE +/− minocycline (30 mg/kg/d, IP) followed by behavioral testing in adulthood. Behavioral testing and age of testing included: locomotor activity and exploration (27–28 weeks), novel object recognition (NORT, 28-30 weeks), 3-chamber sociability and social memory (29–31 weeks), prepulse inhibition (PPI, 30–32 weeks), Morris Water Maze with reversal (MWM, 31–35 weeks), and Piezo sleep monitoring (35–37 weeks). We found that AIE increased levels of neurotoxic Aβ1–42 in adult female hippocampus as well as intraneuronal Aβ1–42 in amygdala and entorhinal cortex. Phosphorylated tau at residue Thr181 (p-tau-181) was also increased in female hippocampus by AIE. Several proinflammatory genes were persistently increased by AIE in the female hippocampus, including IL-1β, MCP-1, IL-6, and IFNα. Expression of these genes was strongly correlated with the levels of Aβ1–42 and p-tau-181 in hippocampus. AIE caused persistent decreases in locomotor activity (open-field and NORT habituation) and increased anxiety-like behavior (thigmotaxis) while reducing memory retention. Treatment with the anti-inflammatory compound minocycline during AIE blocked persistent increases in Aβ1–42 in amygdala and p-tau-181 in hippocampus, and prevented AIE-induced thigmotaxis and memory loss. Together, these data find that adolescent binge ethanol enhances AD molecular and behavioral pathology in adulthood through proinflammatory signaling. Blockade of proinflammatory signaling during ethanol exposure prevents ethanol-induced effects on pathologic accumulation of AD-associated proteins and persistent behavior changes relevant to human AD

Reversal of social deficits by subchronic oxytocin in two autism mouse models

Social deficits are a hallmark feature of autism spectrum disorder (ASD) and related developmental syndromes. Although there is no standard treatment for social dysfunction, clinical studies have identified oxytocin as a potential therapeutic with prosocial efficacy. We have previously reported that peripheral oxytocin treatment can increase sociability and ameliorate repetitive stereotypy in adolescent mice from the C58/J model of ASD-like behavior. In the present study, we determined that prosocial oxytocin effects were not limited to the adolescent period, since C58/J mice, tested in adulthood, demonstrated significant social preference up to 2 weeks following subchronic oxytocin treatment. Oxytocin was also evaluated in adult mice with underexpression of the N-methyl-D-aspartate receptor NR1 subunit (encoded by Grin1), a genetic model of autism- and schizophrenia- like behavior. Subchronic oxytocin had striking prosocial efficacy in male Grin1 knockdown mice; in contrast, chronic regimens with clozapine (66 mg/kg/day) or risperidone (2 mg/kg/day) failed to reverse deficits in sociability. Neither the subchronic oxytocin regimen, nor chronic treatment with clozapine or risperidone, reversed impaired prepulse inhibition in the Grin1 knockdown mice. Overall, these studies demonstrate oxytocin can enhance sociability in mouse models with divergent genotypes and behavioral profiles, adding to the evidence that this neurohormone could have therapeutic prosocial efficacy across a spectrum of developmental disorders

Disruption of social approach by MK-801, amphetamine, and fluoxetine in adolescent C57BL/6J mice

Autism is a severe neurodevelopmental disorder, diagnosed on the basis of core behavioral symptoms. Although the mechanistic basis for the disorder is not yet known, genetic analyses have suggested a role for abnormal excitatory/inhibitory signaling systems in brain, including dysregulation of glutamatergic neurotransmission. In mice, the constitutive knockdown of NMDA receptors leads to social deficits, repetitive behavior, and self-injurious responses that reflect aspects of the autism clinical profile. However, social phenotypes differ with age: mice with reduced NMDA-receptor function exhibit hypersociability in adolescence, but markedly deficient sociability in adulthood. The present studies determined whether acute disruption of NMDA neurotransmission leads to exaggerated social approach, similar to that observed with constitutive disruption, in adolescent C57BL/6J mice. The effects of MK-801, an NMDA receptor antagonist, were compared with amphetamine, a dopamine agonist, and fluoxetine, a selective serotonin reuptake inhibitor, on performance in a three-chamber choice task. Results showed that acute treatment with MK-801 led to social approach deficits at doses without effects on entry numbers. Amphetamine also decreased social preference, but increased number of entries at every dose. Fluoxetine (10 mg/kg) had selective effects on social novelty preference. Withdrawal from a chronic ethanol regimen decreased activity, but did not attenuate sociability. Low doses of MK-801 and amphetamine were also evaluated in a marble-burying assay for repetitive behavior. MK-801, at a dose that did not disrupt sociability or alter entries, led to a profound reduction in marble-burying. Overall, these findings demonstrate that moderate alteration of NMDA, dopamine, or serotonin function can attenuate social preference in wild type mice

Repetitive behavior profile and supersensitivity to amphetamine in the C58/J mouse model of autism

Restricted repetitive behaviors are core symptoms of autism spectrum disorders (ASDs). The range of symptoms encompassed by the repetitive behavior domain includes lower-order stereotypy and self-injury, and higher-order indices of circumscribed interests and cognitive rigidity. Heterogeneity in clinical ASD profiles suggests that specific manifestations of repetitive behavior reflect differential neuropathology. The present studies utilized a set of phenotyping tasks to determine a repetitive behavior profile for the C58/J mouse strain, a model of ASD core symptoms. In an observational screen, C58/J demonstrated overt motor stereotypy, but not over-grooming, a commonly-used measure for mouse repetitive behavior. Amphetamine did not exacerbate motor stereotypy, but had enhanced stimulant effects on locomotion and rearing in C58/J, compared to C57BL/6J. Both C58/J and Grin1 knockdown mice, another model of ASD-like behavior, had marked deficits in marble-burying. In a nose poke task for higher-order repetitive behavior, C58/J had reduced holeboard exploration and preference for non-social, versus social, olfactory stimuli, but did not demonstrate cognitive rigidity following familiarization to an appetitive stimulus. Analysis of available high-density genotype data indicated specific regions of divergence between C58/J and two highly-sociable strains with common genetic lineage. Strain genome comparisons identified autism candidate genes, including Cntnap2 and Slc6a4, located within regions divergent in C58/J. However, Grin1, Nlgn1, Sapap3, and Slitrk5, genes linked to repetitive over-grooming, were not in regions of divergence. These studies suggest that specific repetitive phenotypes can be used to distinguish ASD mouse models, with implications for divergent underlying mechanisms for different repetitive behavior profiles

Prosocial effects of oxytocin in two mouse models of autism spectrum disorders

Clinical evidence suggests that oxytocin treatment improves social deficits and repetitive behavior in autism spectrum disorders (ASDs). However, the neuropeptide has a short plasma half-life and poor ability to penetrate the blood-brain barrier. In order to facilitate the development of more bioavailable oxytocinergic compounds as therapeutics to treat core ASD symptoms, small animal models must be validated for preclinical screens. This study examined the preclinical utility of two inbred mouse strains, BALB/cByJ and C58/J, that exhibit phenotypes relevant to core ASD symptoms. Mice from both strains were intraperitoneally administered oxytocin, using either acute or sub-chronic regimens. Acute oxytocin did not increase sociability in BALB/cByJ; however, sub-chronic oxytocin had significant prosocial effects in both BALB/cByJ and C58/J. Increased sociability was observed 24 hours following the final oxytocin dose in BALB/cByJ, while prosocial effects of oxytocin emerged 1–2 weeks post-treatment in C58/J. Furthermore, acute oxytocin decreased motor stereotypy in C58/J and did not induce hypoactivity or anxiolytic-like effects in an open field test. This study demonstrates that oxytocin administration can attenuate social deficits and repetitive behavior in mouse models of ASD, dependent on dose regimen and genotype. These findings provide validation of the BALB/cByJ and C58/J models as useful platforms for screening novel drugs for intervention in ASDs and for elucidating the mechanisms contributing to the prosocial effects of oxytocin

Allosteric ligands for the pharmacologically dark receptors GPR68 and GPR65

At least 120 non-olfactory G protein-coupled receptors in the human genome are ”orphans” for which endogenous ligands are unknown, and many have no selective ligands, hindering elucidation of their biological functions and clinical relevance. Among these is GPR68, a proton receptor that lacks small molecule modulators for probing its biology. Yeast-based screens against GPR68 identified the benzodiazepine drug lorazepam as a non-selective GPR68 positive allosteric modulator. Over 3000 GPR68 homology models were refined to recognize lorazepam in a putative allosteric site. Docking 3.1 million molecules predicted new GPR68 modulators many of which were confirmed in functional assays. One potent GPR68 modulator—ogerin– suppressed recall in fear conditioning in wild-type, but not in GPR68 knockout mice. The same approach led to the discovery of allosteric agonists and negative allosteric modulators for GPR65. Combining physical and structure-based screening may be broadly useful for ligand discovery for understudied and orphan GPCRs

Cks1 Is Required for Tumor Cell Proliferation but Not Sufficient to Induce Hematopoietic Malignancies

The Cks1 component of the SCFSkp2 complex is necessary for p27Kip1 ubiquitylation and degradation. Cks1 expression is elevated in various B cell malignancies including Burkitt lymphoma and multiple myeloma. We have previously shown that loss of Cks1 results in elevated p27Kip1 levels and delayed tumor development in a mouse model of Myc-induced B cell lymphoma. Surprisingly, loss of Skp2 in the same mouse model also resulted in elevated p27Kip1 levels but exhibited no impact on tumor onset. This raises the possibility that Cks1 could have other oncogenic activities than suppressing p27Kip1. To challenge this notion we have targeted overexpression of Cks1 to B cells using a conditional retroviral bone marrow transduction-transplantation system. Despite potent ectopic overexpression, Cks1 was unable to promote B cell hyperproliferation or B cell malignancies, indicating that Cks1 is not oncogenic when overexpressed in B cells. Since Skp2 overexpression can drive T-cell tumorigenesis or other cancers we also widened the quest for oncogenic activity of Cks1 by ubiquitously expressing Cks1 in hematopoetic progenitors. At variance with c-Myc overexpression, which caused acute myeloid leukemia, Cks1 overexpression did not induce myeloproliferation or leukemia. Therefore, despite being associated with a poor prognosis in various malignancies, sole Cks1 expression is insufficient to induce lymphoma or a myeloproliferative disease in vivo

The prevalence and incidence of Irritable Bowel Syndrome and Inflammatory Bowel Disease in depression and bipolar disorder: a systematic review and meta-analysis

Objective: The increased prevalence and incidence of affective disorders among patients with gastrointestinal disease have been well established. However, few studies have investigated the inverse relationship. We aimed to identify all pieces of evidence of the prevalence and incidence of irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD) in people with depression and bipolar disorder. Methods: We conducted a systematic review of studies reporting the association between affective disorders (exposure) and IBS or IBD (outcome) in adults. Evidence was evaluated for quality using Joanna Briggs Institute Critical Appraisal tools. Where suitable data were available, meta-analyses were performed. Results: We identified 18 studies that met the selection criteria, of which 11 provided data on IBS, 5 on IBD, and 2 on both. Overall, people with depression were significantly more likely to have comorbid IBS (risk ratio = 2.42, 95% confidence interval = 1.98-2.96) and to develop new-onset IBS (risk ratio = 1.90, 95% confidence interval = 1.41-2.56) compared with people without depression. They were also more likely to have and develop IBD, and among patients with IBD, significantly increased rates of depression were observed as early as 5 years before diagnosis. Bipolar disorder was not consistently associated with risk of either condition. Conclusions: People with depression are at an increased risk of both having and developing lower gastrointestinal disorders. These findings have important implications for how we understand, manage, and prevent this comorbidity in clinical practice. Further studies are needed to improve our understanding of the relationship between bipolar disorder and bowel disease as well as the role of psychotropic medication, particularly selective serotonin reuptake inhibitors

Amelioration of Muscle and Nerve Pathology in LAMA2 Muscular Dystrophy by AAV9-Mini-Agrin

LAMA2-related muscular dystrophy (LAMA2 MD) is the most common and fatal form of early-onset congenital muscular dystrophies. Due to the large size of the laminin α2 cDNA and heterotrimeric structure of the protein, it is challenging to develop a gene-replacement therapy. Our group has developed a novel adeno-associated viral (AAV) vector carrying the mini-agrin, which is a non-homologous functional substitute for the mutated laminin α2. A significant therapeutic effect in skeletal muscle was observed in our previous study using AAV serotype 1 (AAV1). In this investigation, we examined AAV9 vector, which has more widespread transduction than AAV1, to determine if the therapeutic effects could be further improved. As expected, AAV9-mini-agrin treatment offered enhanced therapeutic effects over the previously used AAV1-mini-agrin in extending mouse lifespan and improvement of muscle pathology. Additionally, overexpression of mini-agrin in peripheral nerves of dyw/dyw mice partially amended nerve pathology as evidenced by improved motor function and sensorimotor processing, partial restoration of myelination, partial restoration of basement membrane via EM examination, as well as decreased regeneration of Schwann cells. In conclusion, our studies indicate that overexpression of mini-agrin into dyw/dyw mice offers profound therapeutic effects in both skeletal muscle and nervous system. Keywords: LAMA2, mini-agrin, muscular dystrophy, CMD, AAV, gene therap