Location- and sex-specific differences in weight and motor coordination in two commonly used mouse strains

Four-parameter analysis in modified Rotarod test for detecting minor motor deficits in mice

BACKGROUND

The Rotarod test with commercial apparatus is widely used to assess locomotor performance, balance and motor learning as well as the deficits resulting from diverse neurological disorders in laboratory rodents due to its simplicity and objectivity. Traditionally, the test ends when rodents drop from the accelerating, turning rod, and the only parameter used commonly is "latency to fall". The values of individual animals can often vary greatly.

RESULTS

In the present study, we established a procedure for mice with 4 consecutive days of training with 4 trials per day and modified the testing procedure by placing the mice back on the rod repeatedly after each fall until the trial ends (5 min). Data from the fourth training day as baseline results showed that the second, third and fourth trial were more consistent than the first, probably due to habituation or learning. There was no difference between the second, third and fourth trial, two trials may be sufficient in testing. We also introduced 3 additional read-outs: Longest duration on the rod (s), Maximal distance covered (cm), and Number of falls to better evaluate the motor capacity over the 5 min of testing. We then used this 4-parameter analysis to capture the motor deficits of mice with mild to moderate traumatic brain injuries (by a weight dropping on the skull (Marmarou model)). We found that normalization of data to individual baseline performance was needed to reduce individual differences, and 4 trials were more sensitive than two to show motor deficits. The parameter of Maximal distance was the best in detecting statistically significant long-term motor deficits.

CONCLUSIONS

These results show that by making adjustments to the protocol and employing a more refined analysis, it is possible to expand a widely used routine behavioral test with additional accessible parameters that detect relevant deficits in a model of mild to moderate traumatic brain injury. The modified Rotarod test maybe a valuable tool for better preclinical evaluations of drugs and therapies.

Structural MRI Reveals Cervical Spinal Cord Atrophy in the P301L Mouse Model of Tauopathy: Gender and Transgene-Dosing Effects

In primary tauopathies, the deposition of tau neurofibrillary tangles and threads as well as neurodegenerative changes have been found within the brain and spinal cord. While degenerative changes have been intensively studied in the brain using structural magnetic resonance imaging (MRI), MRI studies investigating the spinal cord are still scarce. In the present study, we acquired ex vivo high resolution structural MRI of the cervical spinal cord of 8.5–9 month old hemizygous and homozygous P301L mice and non-transgenic littermates of both genders. We assessed the total cross-sectional area, and the gray and white matter anterior-posterior width and left-right width that are established imaging marker of spinal cord degeneration. We observed significant tissue-specific reductions in these parameters in female P301L mice that were stronger in homozygous than in hemizygous P301L mice, indicating both an effect of gender and transgene expression on cervical spinal cord atrophy. Moreover, atrophy was stronger in the gray matter than in the white matter. Immunohistochemical analysis revealed neurodegenerative and neuroinflammatory changes in the cervical spinal cord in both the gray and white matter of P301L mice. Collectively, our results provide evidence for cervical spinal cord atrophy that may directly contribute to the motor signs associated with tauopathy.

Comprehensive characterization of motor and coordination functions in three adolescent wild-type mouse strains

Neuropsychiatric disorders are often associated with motor and coordination abnormalities that have important implications on the etiology, pathophysiology, and management of these disorders. Although the onset of many neuropsychiatric disorders including autism spectrum disorder, schizophrenia, and attention-deficit hyperactivity disorder emerges mainly during infancy and adolescence, most of the behavioral studies in mice modeling neuropsychiatric phenotypes are performed in adult animals, possibly missing valuable phenotypic information related to the effect of synaptic maturation during development. Here, we examined which behavioral tests assessing both motor and coordination functions can be performed in mice at two different adolescent stages. As strain and sex affect mouse behavior, our experiments covered both male and female mice of three inbred wild-type strains, C57BL/6N, DBA/2, and FVB/N. Adolescent mice of both postnatal days (P)22-30 and P32-40 developmental stages were capable of mastering common motor and coordination tests. However, results differed significantly between strains and sexes. Moreover, the 10-day interval between the two tested cohorts uncovered a strong difference in the behavioral results, confirming the significant impact of maturation on behavioral patterns. Interestingly, the results of distinct behavioral experiments were directly correlated with the weight of mice, which may explain the lack of reproducibility of some behavioral results in genetically-modified mice. Our study paves the way for better reproducibility of behavioral tests by addressing the effect of the developmental stage, strain, sex, and weight of mice on achieving the face validity of neuropsychiatric disorder-associated motor dysfunctions.

Age related weight loss in female 5xFAD mice from 3 to 12 months of age

In addition to cognitive decline, patients with Alzheimer's disease (AD) exhibit sensory, motor, and neuropsychiatric deficits. Many AD patients also show weight loss, suggesting that AD may involve a metabolic syndrome. The 5xFAD mouse model shows age-related weight loss compared to wildtype controls, and thus may exhibit metabolic dysfunction. This longitudinal study measured age-related weight loss in female 5xFAD and B6SJL/JF2 wild-type mice from 3 to 12 months of age, and examines some of the behavioural and physiological phenotypes in these mice that have been proposed to contribute to this weight loss. Because some mice had to be singly housed during the study, we also examined genotype by housing interactions. The 5xFAD mice weighed less and ate less than WT littermates starting at 6 months of age, exhibited less home cage activity, had higher frailty scores, less white adipose tissue, and lower leptin expression. At 9 and 12 months of age, heavier 5xFAD mice performed better on the rotarod, suggesting that metabolic deficits which begin between 6 and 9 months of age may exacerbate the behavioural deficits in 5xFAD mice. These results indicate that the 5xFAD mouse is a useful model to study the behavioural and metabolic changes in AD.

Sex differences in age-related impairments vary across cognitive and physical assessments in rats

Inclusion of female subjects in preclinical biomedical research is imperative for understanding mechanisms of age-related cognitive decline, as more than half of individuals older than 65 are female. In rodents, however, few behavioral and physical assessments have been conducted in both sexes within the same study. The current article documents data obtained from young and aged rats of both sexes that performed a battery of cognitive and physical assessments to examine for potential interactions between sex and age. Physical performance was measured with a rotarod test of motor coordination, assessment of maximum grip strength, and swim speed. While females outperformed males in rotarod and grip strength, there was also an age-dependent decline in physical performance in both sexes. Cognitive assessments included the Morris watermaze test of hippocampal dependent spatial memory and a biconditional association task with a working memory (WM) component, both of which were not significantly different across sex. Notably, a cognitive dual task that simultaneously tests working memory (WM) and biconditional association task (BAT) acquisition has previously been shown to be more sensitive to age-related cognitive decline than the watermaze in male rats, which is replicated here in both female and male rats. Furthermore, young and aged females (<27 months) spent a similar percent of time in each estrus cycle phase and phase did not influence WM/BAT performance. Future studies utilizing similar behavioral paradigms to examine the neurobiology of cognitive aging should be representative of the human population they intend to model through the inclusion of female subjects. (PsycINFO Database Record (c) 2020 APA, all rights reserved).

Long-term HIV-1 Tat Expression in the Brain Led to Neurobehavioral, Pathological, and Epigenetic Changes Reminiscent of Accelerated Aging

HIV infects the central nervous system and causes HIV/neuroAIDS, which is predominantly manifested in the form of mild cognitive and motor disorder in the era of combination antiretroviral therapy. HIV Tat protein is known to be a major pathogenic factor for HIV/neuroAIDS through a myriad of direct and indirect mechanisms. However, most, if not all of studies involve short-time exposure of recombinant Tat protein in vitro or short-term Tat expression in vivo. In this study, we took advantage of the doxycycline-inducible brain-specific HIV-1 Tat transgenic mouse model, fed the animals for 12 months, and assessed behavioral, pathological, and epigenetic changes in these mice. Long-term Tat expression led to poorer short-and long-term memory, lower locomotor activity and impaired coordination and balance ability, increased astrocyte activation and compromised neuronal integrity, and decreased global genomic DNA methylation. There were sex- and brain region-dependent differences in behaviors, pathologies, and epigenetic changes resulting from long-term Tat expression. All these changes are reminiscent of accelerated aging, raising the possibility that HIV Tat contributes, at least in part, to HIV infection-associated accelerated aging in HIV-infected individuals. These findings also suggest another utility of this model for HIV infection-associated accelerated aging studies.

Changes in motor behavior, neuropathology, and gut microbiota of a Batten disease mouse model following administration of acidified drinking water

CLN3 mutations cause the fatal neurodegenerative disorder, CLN3 Batten disease. The Cln3^−/− mouse model displays characteristic features of the human disease including motor deficits. When mice received acidified drinking water (pH 2.5–2.9) instead of normal tap water (pH 8.4) for several generations, the motor skills of Cln3^−/− mice normalized to control levels, indicating a disease-modifying effect of acidified water. Here we investigated if acidified water administered from postnatal day 21 has therapeutic benefits in Cln3^−/− mice. Indeed, acidified water temporarily attenuated the motor deficits, had beneficial effects on behavioral parameters and prevented microglial activation in the brain of Cln3^−/− mice. Interestingly, in control mice, acidified drinking water caused brain region-specific glial activation and significant changes in motor performance. Since the gut microbiota can influence neurological functions, we examined it in our disease model and found that the gut microbiota of Cln3^−/− mice was markedly different from control mice, and acidified water differentially changed the gut microbiota composition in these mice. These results indicate that acidified water may provide therapeutic benefit to CLN3 Batten disease patients, and that the pH of drinking water is a major environmental factor that strongly influences the results of murine behavioral and pathological studies.

FGF-2 isoforms influence the development of dopaminergic neurons in the murine substantia nigra, but not anxiety-like behavior, stress susceptibility, or locomotor behavior

BACKGROUND

Loss of fibroblast growth factor 2 (FGF-2) is responsible for the development of an increased number of dopaminergic (DA) neurons in the murine substantia nigra pars compacta (SNpc). Furthermore, dysregulation of its expression patterns within the central nervous system (CNS) is associated with behavioral abnormalities in mice. Until now, the contributions of the individual FGF-2 isoforms (one low (LMW) and two high molecular weight (HMW) isoforms) in the CNS are elusive.

METHODS

To unravel the specific effects of FGF-2 isoforms, we compared three knockout mouse lines, one only deficient for LMW, one deficient for HMW and another lacking both isoforms, regarding DA neuronal development. With this regard, three time points of ontogenic development of the SNpc were stereologically investigated. Furthermore, behavioral aspects were analyzed in young adult mice, supplemented by corticosterone measurements.

RESULTS

Juvenile mice lacking either LMW or HMW develop equal supernumerary DA neuron numbers in the SNpc. Compensatory increased LMW expression is observed in animals lacking HMW. Meanwhile, no knockout mouse line demonstrated changes in anxiety-like behavior, stress susceptibility, or locomotor behavior.

CONCLUSIONS

Both FGF-2 isoforms crucially influence DA neuronal development in the murine SNpc. However, absence of LMW or HMW alone alters neither anxiety-like nor locomotor behavior, or stress susceptibility. Therefore, FGF-2 is not a determinant and causative factor for behavioral alterations alone, but probably in combination with appropriate conditions, like environmental or genetic factors.

Analysis of Motor Function in Amyloid Precursor-Like Protein 2 Knockout Mice: The Effects of Ageing and Sex

The amyloid precursor protein (APP) is a member of a conserved gene family that includes the amyloid precursor-like proteins 1 (APLP1) and 2 (APLP2). APP and APLP2 share a high degree of similarity, and have overlapping patterns of spatial and temporal expression in the central and peripheral tissues, in particular at the neuromuscular junction. APP-family knockout (KO) studies have helped elucidate aspects of function and functional redundancy amongst the APP-family members. In the present study, we investigated motor performance of APLP2-KO mice and the effect sex differences and age-related changes have on motor performance. APLP2-KO and WT (on C57Bl6 background) littermates control mice from 8 (young adulthood) to 48 weeks (middle age) were investigated. Analysis of motor neuron and muscle morphology showed APLP2-KO females but not males, had less age-related motor function impairments. We observed age and sex differences in both motor neuron number and muscle fiber size distribution for APLP2-KO mice compared to WT (C57Bl6). These alterations in the motor neuron number and muscle fiber distribution pattern may explain why female APLP2-KO mice have far better motor function behaviour during ageing.

A behavioral test battery for mouse models of Angelman syndrome: a powerful tool for testing drugs and novel Ube3a mutants

Background

Angelman syndrome (AS) is a neurodevelopmental disorder caused by mutations affecting UBE3A function. AS is characterized by intellectual disability, impaired motor coordination, epilepsy, and behavioral abnormalities including autism spectrum disorder features. The development of treatments for AS heavily relies on the ability to test the efficacy of drugs in mouse models that show reliable, and preferably clinically relevant, phenotypes. We previously described a number of behavioral paradigms that assess phenotypes in the domains of motor performance, repetitive behavior, anxiety, and seizure susceptibility. Here, we set out to evaluate the robustness of these phenotypes when tested in a standardized test battery. We then used this behavioral test battery to assess the efficacy of minocycline and levodopa, which were recently tested in clinical trials of AS.

Methods

We combined data of eight independent experiments involving 111 Ube3a mice and 120 wild-type littermate control mice. Using a meta-analysis, we determined the statistical power of the subtests and the effect of putative confounding factors, such as the effect of sex and of animal weight on rotarod performance. We further assessed the robustness of these phenotypes by comparing Ube3a mutants in different genetic backgrounds and by comparing the behavioral phenotypes of independently derived Ube3a-mutant lines. In addition, we investigated if the test battery allowed re-testing the same animals, which would allow a within-subject testing design.

Results

We find that the test battery is robust across different Ube3a-mutant lines, but confirm and extend earlier studies that several phenotypes are very sensitive to genetic background. We further found that the audiogenic seizure susceptibility phenotype is fully reversible upon pharmacological treatment and highly suitable for dose-finding studies. In agreement with the clinical trial results, we found that minocycline and levodopa treatment of Ube3a mice did not show any sign of improved performance in our test battery.

Conclusions

Our study provides a useful tool for preclinical drug testing to identify treatments for Angelman syndrome. Since the phenotypes are observed in several independently derived Ube3a lines, the test battery can also be employed to investigate the effect of specific Ube3a mutations on these phenotypes.

Searching for novel biomarkers using a mouse model of CLN3-Batten disease

CLN3-Batten disease is a rare, autosomal recessive disorder involving seizures, visual, motor and cognitive decline, and premature death. The Cln3Δex7/8 mouse model recapitulates several phenotypic characteristics of the most common 1.02kb disease-associated deletion. Identification of reproducible biomarker(s) to facilitate longitudinal monitoring of disease progression and provide readouts for therapeutic response has remained elusive. One factor that has complicated the identification of suitable biomarkers in this mouse model has been that variations in animal husbandry appear to significantly influence readouts. In the current study, we cross-compared a number of biological parameters in blood from Cln3Δex7/8 mice and control, non-disease mice on the same genetic background from multiple animal facilities in an attempt to better define a surrogate marker of CLN3-Batten disease. Interestingly, we found that significant differences between Batten and non-disease mice found at one site were generally not maintained across different facilities. Our results suggest that colony variation in the Cln3Δex7/8 mouse model of CLN3-Batten disease can influence potential biomarkers of the disease.

Taurine Administration Recovers Motor and Learning Deficits in an Angelman Syndrome Mouse Model

Angelman syndrome (AS, MIM 105830) is a rare neurodevelopmental disorder affecting 1:10–20,000 children. Patients show moderate to severe intellectual disability, ataxia and absence of speech. Studies on both post-mortem AS human brains and mouse models revealed dysfunctions in the extra synaptic gamma-aminobutyric acid (GABA) receptors implicated in the pathogenesis. Taurine is a free intracellular sulfur-containing amino acid, abundant in brain, considered an inhibiting neurotransmitter with neuroprotective properties. As taurine acts as an agonist of GABA-A receptors, we aimed at investigating whether it might ameliorate AS symptoms. Since mice weaning, we orally administered 1 g/kg/day taurine in water to Ube3a-deficient mice. To test the improvement of motor and cognitive skills, Rotarod, Novel Object Recognition and Open Field tests were assayed at 7, 14, 21 and 30 weeks, while biochemical tests and amino acid dosages were carried out, respectively, by Western-blot and high-performance liquid chromatography (HPLC) on frozen whole brains. Treatment of Ube3a^m−/p+ mice with taurine significantly improved motor and learning skills and restored the levels of the post-synaptic PSD-95 and pERK1/2-ERK1/2 ratio to wild type values. No side effects of taurine were observed. Our study indicates taurine administration as a potential therapy to ameliorate motor deficits and learning difficulties in AS.

Enhanced synaptic plasticity and spatial memory in female but not male FLRT2-haplodeficient mice

The Fibronectin Leucine-Rich Transmembrane protein 2 (FLRT2) has been implicated in several hormone -and sex-dependent physiological and pathological processes (including chondrogenesis, menarche and breast cancer); is known to regulate developmental synapses formation, and is expressed in the hippocampus, a brain structure central for learning and memory. However, the role of FLRT2 in the adult hippocampus and its relevance in sex-dependent brain functions remains unknown. We here used adult single-allele FLRT2 knockout (FLRT2+/-) mice and behavioral, electrophysiological, and molecular/biological assays to examine the effects of FLRT2 haplodeficiency on synaptic plasticity and hippocampus-dependent learning and memory. Female and male FLRT2+/- mice presented morphological features (including body masses, brain shapes/weights, and brain macroscopic cytoarchitectonic organization), indistinguishable from their wild type counterparts. However, in vivo examinations unveiled enhanced hippocampus-dependent spatial memory recall in female FLRT2+/- animals, concomitant with augmented hippocampal synaptic plasticity and decreased levels of the glutamate transporter EAAT2 and beta estrogen receptors. In contrast, male FLRT2+/- animals exhibited deficient memory recall and decreased alpha estrogen receptor levels. These observations propose that FLRT2 can regulate memory functions in the adulthood in a sex-specific manner and might thus contribute to further research on the mechanisms linking sexual dimorphism and cognition.

SLC39A14 deficiency alters manganese homeostasis and excretion resulting in brain manganese accumulation and motor deficits in mice

Solute carrier family 39, member 14 (SLC39A14) is a transmembrane transporter that can mediate the cellular uptake of zinc, iron, and manganese (Mn). Studies of Slc39a14 knockout (Slc39a14^-/-) mice have documented that SLC39A14 is required for systemic growth, hepatic zinc uptake during inflammation, and iron loading of the liver in iron overload. The normal physiological roles of SLC39A14, however, remain incompletely characterized. Here, we report that Slc39a14^-/- mice spontaneously display dramatic alterations in tissue Mn concentrations, suggesting that Mn is a main physiological substrate for SLC39A14. Specifically, Slc39a14^-/- mice have abnormally low Mn levels in the liver coupled with markedly elevated Mn concentrations in blood and most other organs, especially the brain and bone. Radiotracer studies using ⁵⁴Mn reveal that Slc39a14^-/- mice have impaired Mn uptake by the liver and pancreas and reduced gastrointestinal Mn excretion. In the brain of Slc39a14^-/- mice, Mn accumulated in the pons and basal ganglia, including the globus pallidus, a region susceptible to Mn-related neurotoxicity. Brain Mn accumulation in Slc39a14^-/- mice was associated with locomotor impairments, as assessed by various behavioral tests. Although a low-Mn diet started at weaning was able to reverse brain Mn accumulation in Slc39a14^-/- mice, it did not correct their motor deficits. We conclude that SLC39A14 is essential for efficient Mn uptake by the liver and pancreas, and its deficiency results in impaired Mn excretion and accumulation of the metal in other tissues. The inability of Mn depletion to correct the motor deficits in Slc39a14^-/- mice suggests that the motor impairments represent lasting effects of early-life Mn exposure.

A tailored mouse model of CLN2 disease: A nonsense mutant for testing personalized therapies

The Neuronal Ceroid Lipofuscinoses (NCLs), also known as Batten disease, result from mutations in over a dozen genes. Although, adults are susceptible, the NCLs are frequently classified as pediatric neurodegenerative diseases due to their greater pediatric prevalence. Initial clinical presentation usually consists of either seizures or retinopathy but develops to encompass both in conjunction with declining motor and cognitive function. The NCLs result in premature death due to the absence of curative therapies. Nevertheless, preclinical and clinical trials exist for various therapies. However, the genotypes of NCL animal models determine which therapeutic approaches can be assessed. Mutations of the CLN2 gene encoding a soluble lysosomal enzyme, tripeptidyl peptidase 1 (TPP1), cause late infantile NCL/CLN2 disease. The genotype of the original mouse model of CLN2 disease, Cln2^-/-, excludes mutation guided therapies like antisense oligonucleotides and nonsense suppression. Therefore, the purpose of this study was to develop a model of CLN2 disease that allows for the assessment of all therapeutic approaches. Nonsense mutations in CLN2 disease are frequent, the most common being CLN2^R208X. Thus, we created a mouse model that carries a mutation equivalent to the human p.R208X mutation. Molecular assessment of Cln2^R207X/R207X tissues determined significant reduction in Cln2 transcript abundance and TPP1 enzyme activity. This reduction leads to the development of neurological impairment (e.g. tremors) and neuropathology (e.g. astrocytosis). Collectively, these assessments indicate that the Cln2^R207X/R207X mouse is a valid CLN2 disease model which can be used for the preclinical evaluation of all therapeutic approaches including mutation guided therapies.

Finding the most appropriate mouse model of juvenile CLN3 (Batten) disease for therapeutic studies: the importance of genetic background and gender

Mutations in the CLN3 gene cause a fatal neurodegenerative disorder: juvenile CLN3 disease, also known as juvenile Batten disease. The two most commonly utilized mouse models of juvenile CLN3 disease are Cln3-knockout (Cln3^−/−) and Cln3^Δex7/8-knock-in mice, the latter mimicking the most frequent disease-causing human mutation. To determine which mouse model has the most pronounced neurological phenotypes that can be used as outcome measures for therapeutic studies, we compared the exploratory activity, motor function and depressive-like behavior of 1-, 3- and 6-month-old Cln3^−/− and Cln3^Δex7/8-knock-in mice on two different genetic backgrounds (129S6/SvEv and C57BL/6J). Although, in many cases, the behavior of Cln3^−/− and Cln3^Δex7/8 mice was similar, we found genetic-background-, gender- and age-dependent differences between the two mouse models. We also observed large differences in the behavior of the 129S6/SvEv and C57BL/6J wild-type strains, which highlights the strong influence that genetic background can have on phenotype. Based on our results, Cln3^−/− male mice on the 129S6/SvEv genetic background are the most appropriate candidates for therapeutic studies. They exhibit motor deficits at 1 and 6 months of age in the vertical pole test, and they were the only mice to show impaired motor coordination in the rotarod test at both 3 and 6 months. Cln3^−/− males on the C57BL/6J background and Cln3^Δex7/8 males on the 129S6/SvEv background also provide good outcome measures for therapeutic interventions. Cln3^−/− (C57BL/6J) males had serious difficulties in climbing down (at 1 and 6 months) and turning downward on (at 1, 3 and 6 months) the vertical pole, whereas Cln3^Δex7/8 (129S6/SvEv) males climbed down the vertical pole drastically slower than wild-type males at 3 and 6 months of age. Our study demonstrates the importance of testing mouse models on different genetic backgrounds and comparing males and females in order to find the most appropriate disease model for therapeutic studies.

Identification of genetic factors that modify motor performance and body weight using Collaborative Cross mice

Evidence has emerged that suggests a link between motor deficits, obesity and many neurological disorders. However, the contributing genetic risk factors are poorly understood. Here we used the Collaborative Cross (CC), a large panel of newly inbred mice that captures 90% of the known variation among laboratory mice, to identify the genetic loci controlling rotarod performance and its relationship with body weight in a cohort of 365 mice across 16 CC strains. Body weight and rotarod performance varied widely across CC strains and were significantly negatively correlated. Genetic linkage analysis identified 14 loci that were associated with body weight. However, 45 loci affected rotarod performance, seven of which were also associated with body weight, suggesting a strong link at the genetic level. Lastly, we show that genes identified in this study overlap significantly with those related to neurological disorders and obesity found in human GWA studies. In conclusion, our results provide a genetic framework for studies of the connection between body weight, the central nervous system and behavior.

Autism-Associated Insertion Mutation (InsG) of Shank3 Exon 21 Causes Impaired Synaptic Transmission and Behavioral Deficits

SHANK3 (also known as PROSAP2) is a postsynaptic scaffolding protein at excitatory synapses in which mutations and deletions have been implicated in patients with idiopathic autism, Phelan-McDermid (aka 22q13 microdeletion) syndrome, and other neuropsychiatric disorders. In this study, we have created a novel mouse model of human autism caused by the insertion of a single guanine nucleotide into exon 21 (Shank3(G)). The resulting frameshift causes a premature STOP codon and loss of major higher molecular weight Shank3 isoforms at the synapse. Shank3(G/G) mice exhibit deficits in hippocampus-dependent spatial learning, impaired motor coordination, altered response to novelty, and sensory processing deficits. At the cellular level, Shank3(G/G) mice also exhibit impaired hippocampal excitatory transmission and plasticity as well as changes in baseline NMDA receptor-mediated synaptic responses. This work identifies clear alterations in synaptic function and behavior in a novel, genetically accurate mouse model of autism mimicking an autism-associated insertion mutation. Furthermore, these findings lay the foundation for future studies aimed to validate and study region-selective and temporally selective genetic reversal studies in the Shank3(G/G) mouse that was engineered with such future experiments in mind.

The novel Cln1(R151X) mouse model of infantile neuronal ceroid lipofuscinosis (INCL) for testing nonsense suppression therapy

The neuronal ceroid lipofuscinoses (NCLs), also known as Batten disease, are a group of autosomal recessive neurodegenerative disorders in children characterized by the progressive onset of seizures, blindness, motor and cognitive decline and premature death. Patients with mutations in CLN1 primarily manifest with infantile NCL (INCL or Haltia-Santavuori disease), which is second only to congenital NCL for its age of onset and devastating progression. CLN1 encodes a lysosomal enzyme, palmitoyl-protein thioesterase 1 (PPT1). Nonsense mutations in CLN1 account for 52.3% of all disease causing alleles in infantile NCL, the most common of which worldwide is the p.R151X mutation. Previously, we have shown how nonsense-mediated decay is involved in the degradation of CLN1 mRNA transcripts containing the p.R151X mutation in human lymphoblast cell lines. We have also shown how the read-through drugs gentamicin and ataluren (PTC124) increase CLN1 (PPT1) enzyme activity. Here, we provide the initial characterization of the novel Cln1(R151X) mouse model of infantile neuronal ceroid lipofuscinosis that we have generated. This nonsense mutation model recapitulates the molecular, histological and behavioral phenotypes of the human disease. Cln1(R151X) mice showed a significant decrease in Cln1 mRNA level and PPT1 enzyme activity, accumulation of autofluorescent storage material, astrocytosis and microglial activation in the brain. Behavioral characterization of Cln1(R151X) mice at 3 and 5 months of age revealed significant motor deficits as measured by the vertical pole and rotarod tests. We also show how the read-through compound ataluren (PTC124) increases PPT1 enzyme activity and protein level in Cln1(R151X) mice in a proof-of-principle study.

Zinc transporter 8 (ZnT8) and β cell function

Human pancreatic β cells have exceptionally high zinc content. In β cells the highest zinc concentration is in insulin secretory granules, from which it is cosecreted with the hormone. Uptake of zinc into secretory granules is mainly mediated by zinc transporter 8 (ZnT8), the product of the SLC30A8 [solute carrier family 30 (zinc transporter), member 8] gene. The minor alleles of several single-nucleotide polymorphisms (SNPs) in SLC30A8 are associated with decreased risk of type 2 diabetes (T2D), but the precise mechanisms underlying the protective effects remain uncertain. In this article we review current knowledge of the role of ZnT8 in maintaining zinc homeostasis in β cells, its role in glucose metabolism based on knockout mouse studies, and current theories regarding the link between ZnT8 function and T2D.

The SIRT1 activator SRT1720 extends lifespan and improves health of mice fed a standard diet

The prevention or delay of the onset of age-related diseases prolongs survival and improves quality of life while reducing the burden on the health care system. Activation of sirtuin 1 (SIRT1), an NAD(+)-dependent deacetylase, improves metabolism and confers protection against physiological and cognitive disturbances in old age. SRT1720 is a specific SIRT1 activator that has health and lifespan benefits in adult mice fed a high-fat diet. We found extension in lifespan, delayed onset of age-related metabolic diseases, and improved general health in mice fed a standard diet after SRT1720 supplementation. Inhibition of proinflammatory gene expression in both liver and muscle of SRT1720-treated animals was noted. SRT1720 lowered the phosphorylation of NF-κB pathway regulators in vitro only when SIRT1 was functionally present. Combined with our previous work, the current study further supports the beneficial effects of SRT1720 on health across the lifespan in mice.

A murine model of variant late infantile ceroid lipofuscinosis recapitulates behavioral and pathological phenotypes of human disease

Neuronal ceroid lipofuscinoses (NCLs; also known collectively as Batten Disease) are a family of autosomal recessive lysosomal storage disorders. Mutations in as many as 13 genes give rise to ∼10 variants of NCL, all with overlapping clinical symptomatology including visual impairment, motor and cognitive dysfunction, seizures, and premature death. Mutations in CLN6 result in both a variant late infantile onset neuronal ceroid lipofuscinosis (vLINCL) as well as an adult-onset form of the disease called Type A Kufs. CLN6 is a non-glycosylated membrane protein of unknown function localized to the endoplasmic reticulum (ER). In this study, we perform a detailed characterization of a naturally occurring Cln6 mutant (Cln6^nclf) mouse line to validate its utility for translational research. We demonstrate that this Cln6^nclf mutation leads to deficits in motor coordination, vision, memory, and learning. Pathologically, we demonstrate loss of neurons within specific subregions and lamina of the cortex that correlate to behavioral phenotypes. As in other NCL models, this model displays selective loss of GABAergic interneuron sub-populations in the cortex and the hippocampus with profound, early-onset glial activation. Finally, we demonstrate a novel deficit in memory and learning, including a dramatic reduction in dendritic spine density in the cerebral cortex, which suggests a reduction in synaptic strength following disruption in CLN6. Together, these findings highlight the behavioral and pathological similarities between the Cln6^nclf mouse model and human NCL patients, validating this model as a reliable format for screening potential therapeutics.