Alexander disease is a leukodystrophy caused by gain-of-function mutations in the gene for Glial Fibrillary Acidic Protein (GFAP) which result in accumulation and aggregation of GFAP protein, astrocyte dysfunction, and ultimately developmental delay, failure to thrive, and intellectual and motor impairment. A Gfap+/R237H rat model, designed to mimic the common R239H human variant, meets normal milestones during early postnatal development, but declines dramatically as the rats mature. At severe stages of disease, Gfap+/R237H rats exhibit cognitive and motor deficits and increased mortality. Here we provide a more detailed analysis of the Gfap+/R237H rat with respect to onset of motor impairments and increasing loss of function. We show that Gfap+/R237H rats develop abnormal open field activity as they mature but stabilize with age, and that motor deficits are apparent as early as 4 weeks of age, as demonstrated by poor rotarod performance. We use automated gait analysis to further characterize subtle differences at this early age and demonstrate the progression and persistence of impairment at late stages of disease. In addition, we find evidence for changes in cerebellar size, suggesting a potential neuroanatomical correlate to the observed deficits. The rat model provides a novel system in which to investigate aspects of impaired motor function and central nervous system pathology that are directly relevant to the human disease.

Alexander disease (AxD) is a rare neurological disorder caused by dominant gain-of-function mutations in the gene for glial fibrillary acidic protein. Expression of mutant protein results in astrocyte dysfunction that ultimately leads to developmental delay, failure to thrive, and intellectual and motor impairment. The disease is typically fatal, and at present there are no preventative or effective treatments. To gain a better understanding of the link between astrocyte dysfunction and behavioral deficits in AxD, we have recently developed a rat model that recapitulates many of the clinical features of the disease, including failure to thrive, motor impairment, and white matter deficits. In the present study, we show that both male and female AxD model rats exhibit a neurodegenerative profile with a progressive neuroinflammatory response combined with reduced expression of synaptic and mitochondrial proteins. Consistent with these results, AxD rats show reduced hippocampal long-term potentiation and are cognitively impaired, as demonstrated by poor performance in the Barnes maze and novel object recognition tests. The AxD rat provides a novel model in which to investigate the impact of astrocyte pathology on central nervous system function and provides an essential platform for further development of effective treatments for AxD and potentially other neurodegenerative diseases with astrocyte pathology.

Widespread release of norepinephrine (NE) throughout the forebrain fosters learning and memory via adrenergic receptor (AR) signaling, but the molecular mechanisms are largely unknown. The β 2 AR and its downstream effectors, the trimeric stimulatory G s -protein, adenylyl cyclase (AC), and the cAMP-dependent protein kinase A (PKA), form a unique signaling complex with the L-type Ca 2+ channel (LTCC) Ca V 1.2. Phosphorylation of Ca V 1.2 by PKA on Ser 1928 is required for the upregulation of Ca 2+ influx on β 2 AR stimulation and long-term potentiation induced by prolonged theta-tetanus (PTT-LTP) but not LTP induced by two 1-s-long 100-Hz tetani. However, the function of Ser 1928 phosphorylation in vivo is unknown. Here, we show that S1928A knock-in (KI) mice of both sexes, which lack PTT-LTP, express deficiencies during initial consolidation of spatial memory. Especially striking is the effect of this mutation on cognitive flexibility as tested by reversal learning. Mechanistically, long-term depression (LTD) has been implicated in reversal learning. It is abrogated in male and female S1928A knock-in mice and by β 2 AR antagonists and peptides that displace β 2 AR from Ca V 1.2. This work identifies Ca V 1.2 as a critical molecular locus that regulates synaptic plasticity, spatial memory and its reversal, and LTD. SIGNIFICANCE STATEMENT We show that phosphorylation of the Ca 2+ channel Ca V 1.2 on Ser 1928 is important for consolidation of spatial memory and especially its reversal, and long-term depression (LTD). Identification of Ser 1928 as critical for LTD and reversal learning supports the model that LTD underlies flexibility of reference memory.

Maternal immune dysregulation is a prenatal risk factor for autism spectrum disorder (ASD). Importantly, a clinically relevant connection exists between inflammation and metabolic stress that can result in aberrant cytokine signaling and autoimmunity. In this study we examined the potential for maternal autoantibodies (aAbs) to disrupt metabolic signaling and induce neuroanatomical changes in the brains of exposed offspring. To accomplish this, we developed a model of maternal aAb exposure in rats based on the clinical phenomenon of maternal autoantibody-related ASD (MAR-ASD). Following confirmation of aAb production in rat dams and antigen-specific immunoglobulin G (IgG) transfer to offspring, we assessed offspring behavior and brain structure longitudinally. MAR-ASD rat offspring displayed a reduction in pup ultrasonic vocalizations and a pronounced deficit in social play behavior when allowed to freely interact with a novel partner. Additionally, longitudinal in vivo structural magnetic resonance imaging (sMRI) at postnatal day 30 (PND30) and PND70, conducted in a separate cohort of animals, revealed sex-specific differences in total and regional brain volume. Treatment-specific effects by region appeared to converge on midbrain and cerebellar structures in MAR-ASD offspring. Simultaneously, in vivo 1 H magnetic resonance spectroscopy ( 1 H-MRS) data were collected to examine brain metabolite levels in the medial prefrontal cortex. Results showed that MAR-ASD offspring displayed decreased levels of choline-containing compounds and glutathione, accompanied by increased taurine compared to control animals. Overall, we found that rats exposed to MAR-ASD aAbs present with alterations in behavior, brain structure, and neurometabolites; reminiscent of findings observed in clinical ASD.

Clinical and experimental data collected over the last three decades have shown that the maternal consumption of alcohol during pregnancy can have profound teratological effects on the developing human fetus. Numerous studies have demonstrated that animals exposed prenatally to alcohol exhibit similar dysfunctions. These animal models of Fetal Alcohol Syndrome (FAS) allow researchers to systematically manipulate exposure parameters and to probe the brains of afflicted animals in an attempt to characterize the deleterious effects of alcohol on neural development. The functional integrity of the auditory system has also been examined in FAS using brainstem auditory-evoked potentials. Because the procedures are non-invasive, they are particularly useful in assessing neural transmission of sensory input within the brain. Prenatal alcohol exposure also affected sensory systems. Both visual- and auditory-evoked potentials have been reported to be abnormal in infants exposed prenatally to alcohol. The general findings suggest that alcohol exposure delays development of sensory neural systems.

Carriers of the fragile X premutation (PM) can develop a variety of early neurological symptoms, including depression, anxiety and cognitive impairment as well as being at risk for developing the late-onset fragile X-associated tremor/ataxia syndrome (FXTAS). The absence of effective treatments for FXTAS underscores the importance of developing efficacious therapies to reduce the neurological symptoms in elderly PM carriers and FXTAS patients. A recent preliminary study reported that weekly infusions of Allopregnanolone (Allop) may improve deficits in executive function, learning and memory in FXTAS patients. Based on this study we examined whether Allop would improve neurological function in the aged CGG knock-in (CGG KI) dutch mouse, B6.129P2(Cg)-Fmr1tm2Cgr/Cgr, that models much of the symptomatology in PM carriers and FXTAS patients. Wild type and CGG KI mice received 10 weekly injections of Allop (10 mg/kg, s.c.), followed by a battery of behavioral tests of motor function, anxiety, and repetitive behavior, and 5-bromo-2'-deoxyuridine (BrdU) labeling to examine adult neurogenesis. The results provided evidence that Allop in CGG KI mice normalized motor performance and reduced thigmotaxis in the open field, normalized repetitive digging behavior in the marble burying test, but did not appear to increase adult neurogenesis in the hippocampus. Considered together, these results support further examination of Allop as a therapeutic strategy in patients with FXTAS.

AbstractIntroductionDimethyl sulfoxide (DMSO) is a widely used solvent to dissolve hydrophobic substances for clinical uses and experimental in vivo purposes. While usually regarded safe, our prior studies suggest changes to behavior following DMSO exposure. We therefore evaluated the effects of a five‐day, short‐term exposure to DMSO on postnatal infant rats (P6‐10).MethodsDMSO was intraperitoneally injected for five days at 0.2, 2.0, and 4.0 ml/kg body mass. One cohort of animals was sacrificed 24 hr after DMSO exposure to analyze the neurometabolic changes in four brain regions (cortex, hippocampus, basal ganglia, and cerebellum) by hydrophilic interaction liquid chromatography. A second cohort of animals was used to analyze chronic alterations to behavior and pathological changes to glia and neuronal cells later in life (P21‐P40).Results164 metabolites, including key regulatory molecules (retinoic acid, orotic acid, adrenic acid, and hypotaurine), were found significantly altered by DMSO exposure in at least one of the brain regions at P11 (p < .05). Behavioral tests showed significant hypoactive behavior and decreased social habits to the 2.0 and 4.0 ml DMSO/kg groups (p < .01). Significant increases in number of microglia and astrocytes at P40 were observed in the 4.0 ml DMSO/kg group (at p < .015.)ConclusionsDespite short‐term exposure at low, putatively nontoxic concentrations, DMSO led to changes in behavior and social preferences, chronic alterations in glial cells, and changes in essential regulatory brain metabolites. The chronic neurological effects of DMSO exposure reported here raise concerns about its neurotoxicity and consequent safety in human medical applications and clinical trials.

Alexander disease (AxD) is a devastating leukodystrophy caused by gain-of-function mutations in GFAP, and the only available treatments are supportive. Recent advances in antisense oligonucleotide (ASO) therapy have demonstrated that transcript targeting can be a successful strategy for human neurodegenerative diseases amenable to this approach. We have previously used mouse models of AxD to show that Gfap-targeted ASO suppresses protein accumulation and reverses pathology; however, the mice have a mild phenotype with no apparent leukodystrophy or overt clinical features and are therefore limited for assessing functional outcomes. In this report, we introduce a rat model of AxD that exhibits hallmark pathology with GFAP aggregation in the form of Rosenthal fibers, widespread astrogliosis, and white matter deficits. These animals develop normally during the first postnatal weeks but fail to thrive after weaning and develop severe motor deficits as they mature, with about 14% dying of unknown cause between 6 and 12 weeks of age. In this model, a single treatment with Gfap-targeted ASO provides long-lasting suppression, reverses GFAP pathology, and, depending on age of treatment, prevents or mitigates white matter deficits and motor impairment. In this report, we characterize an improved animal model of AxD with myelin pathology and motor impairment, recapitulating prominent features of the human disease, and use this model to show that ASO therapy has the potential to not only prevent but also reverse many aspects of disease.

INTRODUCTION: Intraventricular hemorrhage (IVH) can result in significant cognitive deficits and spatial memory impairments that can prevent over half of IVH patients from returning to work after recovery. The mechanism of this memory decline, however, is incompletely understood. METHODS: To understand the role of mechanical trauma caused by rapid ventricular expansion vs the presence of blood components, such as thrombin, in IVH deficits, we developed a rodent model of IVH by injecting 200 μL of autologous arterial blood into the animals' ventricles. The IVH animals' memories were then assessed along with sham (no injection), vehicle control (200 μL aCSF), and intraventricular thrombin (IVT) (20 U thrombin in 5 μL aCSF) animals using Morris water maze. RESULTS: The IVH group performed worse on this spatial memory task compared to all other groups, indicating that ventricular expansion and presence of blood components both contribute to memory deficits. Based on magnetic resonance imaging (MRI) results, the IVH group was also the only group that developed persistent hydrocephalus. Contrary to our hypothesis that the cognitive deficits of IVH are due to decreased hippocampal neurogenesis, we did not find any statistical difference in the numbers of dentate gyrus progenitor cells (labeled with BrdU and DCX) or neurons (labeled with NeuN) between the different groups. The number of microglia (labeled with Iba1) was also compared among the groups and found to be not statistically different. The microglia in IVH and vehicle control animals, however, were found to have significantly lower fractal dimension (P < .001) and higher lacunarity (P < .001) numbers compared to those of sham animals, indicating a more activated state, likely caused by the mechanical trauma. CONCLUSION: Based on our results, persistent hydrocephalus microglial activation seem to be the drivers of spatial memory deficit after IVH.

The fragile X premutation is a CGG trinucleotide repeat expansion between 55 and 200 repeats in the 5-untranslated region of the fragile X mental retardation 1 (FMR1) gene. Human carriers of the premutation allele are at risk of developing the late-onset neurodegenerative disorder, fragile X-associated tremor/ataxia syndrome (FXTAS). Characteristic neuropathology associated with FXTAS includes intranuclear inclusions in neurons and astroglia. Previous studies recapitulated these histopathological features in neurons in a knock-in mouse model, but without significant astroglial pathology. To determine the role of astroglia in FXTAS, we generated a transgenic mouse line (Gfa2-CGG99-eGFP) that selectively expresses a 99-CGG repeat expansion linked to an enhanced green fluorescent protein (eGFP) reporter in astroglia throughout the brain, including cerebellar Bergmann glia. Behaviorally these mice displayed impaired motor performance on the ladder-rung test, but paradoxically better performance on the rotarod. Immunocytochemical analysis revealed that CGG99-eGFP co-localized with GFAP and S-100 ss, but not with NeuN, Iba1, or MBP, indicating that CGG99-eGFP expression is specific to astroglia. Ubiquitin-positive intranuclear inclusions were found in eGFP-expressing glia throughout the brain. In addition, intracytoplasmic ubiquitin-positive inclusions were found outside the nucleus in distal astrocyte processes. Intriguingly, intranuclear inclusions, in the absence of eGFP mRNA and eGFP fluorescence, were present in neurons of the hypothalamus and neocortex. Furthermore, intranuclear inclusions in both neurons and astrocytes displayed immunofluorescent labeling for the polyglycine peptide FMRpolyG, implicating FMRpolyG in the pathology found in Gfa2-CGG99 mice. Considered together, these results show that Gfa2-CGG99 expression in mice is sufficient to induce key features of FXTAS pathology, including formation of intranuclear inclusions, translation of FMRpolyG, and deficits in motor function.

Immunoglobulin G (IgG) autoantibodies reactive to fetal brain proteins are present in 23% of mothers of children with ASD, raising the possibility of a maternal autoantibody related (MAR) subtype of ASD. While previous passive transfer animal models have yielded promising results, they did not reflect a constant exposure to the salient autoantibodies throughout gestation, as would be the case in the clinical setting. Here we describe a novel non-passive transfer rat model to directly assess the pathologic significance of prenatal exposure to epitope-specific autoantibodies in generating ASD-relevant behaviors in offspring.

Mutations in the SHANK3 gene have been discovered in autism spectrum disorder (ASD), and the intellectual disability, Phelan‐McDermid Syndrome. This study leveraged a new rat model of Shank3 deficiency to assess complex behavioral phenomena, unique to rats, which display a richer social behavior repertoire than mice. Uniquely detectable emissions of ultrasonic vocalizations (USV) in rats serve as situation‐dependent affective signals and accomplish important communicative functions. We report, for the first time, a call and response acoustic playback assay of bidirectional social communication in juvenile Shank3 rats. Interestingly, we found that Shank3‐deficient null males did not demonstrate the enhanced social approach behavior typically exhibited following playback of pro‐social USV. Concomitantly, we discovered that emission of USV in response to playback was not genotype‐dependent and emitted response calls were divergent in meaning. This is the first report of these socially relevant responses using a genetic model of ASD. A comprehensive and empirical analysis of vigorous play during juvenile reciprocal social interactions further revealed fewer bouts and reduced durations of time spent playing by multiple key parameters, including reduced anogenital sniffing and allogrooming. We further discovered that male null Shank3‐deficient pups emitted fewer isolation‐induced USV than Shank3 wildtype controls. Postnatal whole brain anatomical phenotyping was applied to visualize anatomical substrates that underlie developmental phenotypes. The data presented here lend support for the important role of Shank3 in social communication, the core symptom domain of ASD. By increasing the number of in vivo functional outcome measures, we improved the likelihood for identifying and moving forward with medical interventions. Autism Res 2018, 11: 587–601. © 2018 International Society for Autism Research, Wiley Periodicals, Inc.Lay SummaryClinically relevant outcomes are required to demonstrate the utility of therapeutics. We introduce findings in a rat model, and assess the impact of mutations in Shank3, an autism risk gene. We found that males with deficient expression of Shank3 did not demonstrate typical responses in a bi‐directional social communication test and that social interaction was lower on key parameters. Outcome measures reported herein extend earlier results in mice and capture responses to acoustic calls, which is analogous to measuring receptive and expressive communication.

The prevalence and societal impact of neurodevelopmental disorders (NDDs) continue to increase despite years of research in both patient populations and animal models. There remains an urgent need for translational efforts between clinical and preclinical research to (i) identify and evaluate putative causes of NDD, (ii) determine their underlying neurobiological mechanisms, (iii) develop and test novel therapeutic approaches, and (iv) translate basic research into safe and effective clinical practices. Given the complexity behind potential causes and behaviors affected by NDDs, modeling these uniquely human brain disorders in animals will require that we capitalize on unique advantages of a diverse array of species. While much NDD research has been conducted in more traditional animal models such as the mouse, ultimately, we may benefit from creating animal models with species that have a more sophisticated social behavior repertoire such as the rat (Rattus norvegicus) or species that more closely related to humans, such as the rhesus macaque (Macaca mulatta). Here, we highlight the rat and rhesus macaque models for their role in previous psychological research discoveries, current efforts to understand the neurobiology of NDDs, and focus on the convergence of behavior outcome measures that parallel features of human NDDs.

Maternal infection during pregnancy may increase the risk of offspring neurodevelopmental disorders. The preclinical Polyinosinic-polycytidylic acid (PolyIC) model has become one of the most widely used approaches in maternal immune activation (MIA) research. However, variability in molecular weight may impact the immune activating potential of PolyIC. Nulliparous rats injected with high molecular weight PolyIC exhibit pronounced cytokine response and sickness behavior that was not observed in rats injected low molecular weight PolyIC. Although an essential next step is to extend these studies to pregnant animals, the preliminary results suggest that PolyIC molecular weight is an important experimental design consideration.