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Autistic-like social deficits in hippocampal MeCP2 knockdown rat models are rescued by ketamine.

ABSTRACT: Autism or autism spectrum disorder (ASD) is a behavioral syndrome characterized by persistent deficits in social interaction, and repetitive patterns of behavior, interests, or activities. The gene encoding Methyl-CpG binding protein 2 (MeCP2) is one of a few exceptional genes of established causal effect in ASD. Although genetically engineered mice studies may shed light on how MeCP2 loss affects synaptic activity patterns across the whole brain, such studies are not considered practical in ASD patients due to the overall level of impairment, and are technically challenging in mice. For the first time, we show that hippocampal MeCP2 knockdown produces behavioral abnormalities associated with autism-like traits in rats, providing a new strategy to investigate the efficacy of therapeutics in ASD. Ketamine, an N-Methyl-D-aspartate (NMDA) blocker, has been proposed as a possible treatment for autism. Using the MeCP2 knockdown rats in conjunction with a rat model of valproic acid (VPA)-induced ASD, we examined gene expression and ASD behaviors upon ketamine treatment. We report that the core symptoms of autism in MeCP2 knockdown rats with social impairment recovered dramatically following a single treatment with ketamine. [BMB Reports 2022; 55(5): 238-243].

SUBMITTER: Choi M

PROVIDER: S-EPMC9152577 | biostudies-literature | 2022 May

REPOSITORIES: biostudies-literature

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Autistic-like social deficits in hippocampal MeCP2 knockdown rat models are rescued by ketamine.

Choi Miyeon M Ko Seung Yeon SY Seo Jee Young JY Kim Do Gyeong DG Lee Huiju H Chung Heekyoung H Son Hyeon H

BMB reports 20220501 5

Autism or autism spectrum disorder (ASD) is a behavioral syndrome characterized by persistent deficits in social interaction, and repetitive patterns of behavior, interests, or activities. The gene encoding Methyl-CpG binding protein 2 (MeCP2) is one of a few exceptional genes of established causal effect in ASD. Although genetically engineered mice studies may shed light on how MeCP2 loss affects synaptic activity patterns across the whole brain, such studies are not considered practical in ASD ...[more]

PMID: 35410641

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Project description:The goal of this study was to characterize a novel Mecp2 allele in the laboratory rat, a distinct rodent species from the laboratory mouse with unique features. The allele was created by zinc finger-nuclease (ZFN) targeting (SAGE/Horizon) of the X-linked gene, Methyl-CpG-Binding Protein 2 (Mecp2), resulting in normal Mecp2 RNA abundance, but absent protein in male rats as expected due to the presence of only one copy of mutant Mecp2, and an approximate 50% reduction in female rats as expected from animals that harbor one wild-type copy and one mutant copy of Mecp2. Behavioral characterization of female rats with the Mecp2 ZFN allele and wild-type littermates was conducted, and Mecp2 ZFN/+ female rats showed behavioral phenotypes that were consistent with disease-like features present during the early stages of disease onset in the neurological disorder Rett syndrome. The goal of conducting RNAseq studies was to compare existing gene expression alterations in the Mecp2 rat with one of the most widely studied Mecp2 mouse model. Hypothalami were obtained from males with complete loss of MeCP2 (ZFN/y) and wild-type littermate male rats for RNA-seq studies. Common and unique gene expression alterations among the Mecp2 rodents that were then tested in human Rett and control postmortem brain revealed the benefit of combining findings from both models, suggesting the predictive validity of this approach for future studies for the identification of potential preclinical outcome measures. QPCR validation in an independent set of rats was conducted with a subset of genes from the Mecp2 ZFN rat RNA-seq data as an additional control measure. Taken together, these findings demonstrate that the Mecp2 rat model is a complementary tool with unique features for the study of RTT and highlight the potential benefit of cross-species analyses in identifying potential disease-relevant preclinical outcome measures. Transcriptional profiles of hypothalamic samples obtained from male rats haboring a novel zinc-finger nuclease Mecp2 loss-of-function allele and corresponding wild-type littermate rats were generated using RNA-seq

Project description:BackgroundAutism spectrum disorder (ASD) is characterized by impaired social interactions and repetitive patterns of behavior. Symptoms appear in early life and persist throughout adulthood. Early social stimulation can help reverse some of the symptoms, but the biological mechanisms of these therapies are unknown. By analyzing the effects of early social stimulation on ASD-related behavior in the mouse, we aimed to identify brain structures that contribute to these behaviors.MethodsWe injected pregnant mice with 600-mg/kg valproic acid (VPA) or saline (SAL) at gestational day 12.5 and evaluated the effect of weaning their offspring in cages containing only VPA animals, only SAL animals, or mixed. We analyzed juvenile play at PD21 and performed a battery of behavioral tests in adulthood. We then used preclinical PET imaging for an unbiased analysis of the whole brain of these mice and studied the function of the piriform cortex by c-Fos immunoreactivity and HPLC.ResultsCompared to control animals, VPA-exposed animals play less as juveniles and exhibit a lower frequency of social interaction in adulthood when reared with other VPA mice. In addition, these animals were less likely to investigate social odors in the habituation/dishabituation olfactory test. However, when VPA animals were weaned with control animals, these behavioral alterations were not observed. Interestingly, repetitive behaviors and depression-related behaviors were not affected by social enrichment. We also found that VPA animals present high levels of glucose metabolism bilaterally in the piriform cortex (Pir), a region known to be involved in social behaviors. Moreover, we found alterations in the somatosensory, motor, and insular cortices. Remarkably, these effects were mostly reversed after social stimulation. To evaluate if changes in glucose metabolism in the Pir correlated with changes in neuronal activity, we measured c-Fos immunoreactivity in the Pir and found it increased in animals prenatally exposed to VPA. We further found increased dopamine turnover in the Pir. Both alterations were largely reversed by social enrichment.ConclusionsWe show that early social enrichment can specifically rescue social deficits in a mouse model of ASD. Our results identified the Pir as a structure affected by VPA-exposure and social enrichment, suggesting that it could be a key component of the social brain circuitry.

Project description:Chronic social isolation stress (SIS) induces lasting negative effects on the brain, including memory deficits, cognitive impairments, and mood alterations such as depression and anxiety. All these symptoms, at least in part, reflect reduced hippocampal function. In both clinical and preclinical studies, subanesthetic doses of the NMDA receptor antagonist, ketamine (KET), was shown to have rapid and lasting antidepressant effects. Animal studies have shown that biological sex and levels of gonadal hormones alter the behavioral effects of KET, with ovarian hormones increasing sensitivity to the antidepressant-like effects of KET. Since the hippocampus plays a key role in mediating some of the effects of SIS, and considering that KET at low doses has been shown to rescue some of the behavioral deficits of isolation rearing this study aimed to assess the effects of isolation stress on pre- and post-synaptic hippocampal functions in male and female rats reared in SIS, as well as determine whether some of the physiological deficits can be rescued with a single injection of sub-anesthetic doses of KET. To do this, Sprague-Dawley rats were raised from weaning in either social isolation or with same-sex cage mate for 5 to 7 weeks. Male and female rats in either diestrus of proestrus received a single injection of KET (0, 2.5, or 5.0 mg/kg) three hours prior to termination and collection of acute hippocampal slices for ex vivo electrophysiological field potential recordings. Long-term potentiation (LTP) and paired pulse facilitation (PPF) outputs were assessed in a canonical CA3-CA1 dorsal hippocampal circuit. Our data show that SIS inhibits hippocampal LTP without affecting PPF in male rats, an effect that was rescued by KET. In female rats, isolation stress did not alter LTP, but did reduce PPF - especially when females were tested in diestrus-, an effect that was rescued by KET at the highest dose. Our data thus suggest sex differences in the contribution of pre-and postsynaptic hippocampal compartments in response to stress and KET.

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Autistic-like social deficits in hippocampal MeCP2 knockdown rat models are rescued by ketamine.

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Autistic-like social deficits in hippocampal MeCP2 knockdown rat models are rescued by ketamine.

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