ObjectiveIn this study, we used a systemic Fmr1 knockout in order to investigate both genotype‐ and sex‐specific differences across multiple measures of sociability, repetitive behaviors, activity levels, anxiety, and fear‐related learning and memory.BackgroundFragile X syndrome is the most common monogenic cause of intellectual disability and autism. Few studies to date have examined sex differences in a mouse model of Fragile X syndrome, though clinical data support the idea of differences in both overall prevalence and phenotype between the sexes.MethodsUsing wild‐type and systemic homozygous Fmr1 knockout mice, we assessed a variety of behavioral paradigms in adult animals, including the open field test, elevated plus maze, nose‐poke assay, accelerating rotarod, social partition task, three‐chambered social task, and two different fear conditioning paradigms. Tests were ordered such that the most invasive tests were performed last in the sequence, and testing paradigms for similar behaviors were performed in separate cohorts to minimize testing effects.ResultsOur results indicate several sex‐specific changes in Fmr1 knockout mice, including male‐specific increases in activity levels, and female‐specific increases in repetitive behaviors on both the nose‐poke assay and motor coordination on the accelerating rotarod task. The results also indicated that Fmr1 deletion results in deficits in fear learning and memory across both sexes, and no changes in social behavior across two tasks.ConclusionThese findings highlight the importance of including female subjects in preclinical studies, as simply studying the impact of genetic mutations in males does not yield a complete picture of the phenotype. Further research should explore these marked phenotypic differences among the sexes. Moreover, given that treatment strategies are typically equivalent between the sexes, the results highlight a potential need for sex‐specific therapeutics.

Fragile X Syndrome (FXS) is a neurodevelopmental disorder caused by a trinucleotide (CGG) hyperexpansion in the FMR1 gene, functionally silencing transcription of the fragile x mental retardation protein (FMRP). This disorder is characterized by impaired cognition, communication, and social behavior. The purpose of this study was to investigate the development of ultrasonic vocalization (USV) behavior in a FMR1 deficient mouse model. On postnatal days (PD) 9–14, separate cohorts of FVB/NJ pups were removed from their home cage and isolation-induced USVs were recorded. There were significant genotype- and sex-dependent differences in USV behavior across the different testing days. FMR1 knockout mice showed a significant reduction in vocalizations across all days. There was also a significant difference in vocalizations between male and female mice. We found a significant decrease in total number of calls for KO males on PD9 and PD13, as well as an increase in the total number of calls for KO males on PD12. The KO males also had a significant increase in total call duration on PD12 and a reduction on PD13. The KO female had a significant decrease in the total number of calls on PD9 and PD10. They also had a significant decrease in the total call duration on PD9 and a marginal decrease in total call duration on PD10. These results provide additional evidence for communication deficits in FMR1 deficient mice and provide new insight suggesting sexually dimorphic vocalizations during the neonatal period.

Chronic pain patients suffer a disrupted quality of life not only from the experience of pain itself, but also from comorbid symptoms such as depression, anxiety, cognitive impairment, and sleep disturbances. The heterogeneity of these symptoms support the idea of a major involvement of the cerebral cortex in the chronic pain condition. Accordingly, abundant evidence shows that in chronic pain the activity of the medial prefrontal cortex (mPFC), a brain region that is critical for executive function and working memory, is severely impaired. Excitability of the mPFC depends on the integrated effects of intrinsic excitability and excitatory and inhibitory inputs. The main extracortical sources of excitatory input to the mPFC originate in the thalamus, hippocampus, and amygdala, which allow the mPFC to integrate multiple information streams necessary for cognitive control of pain including sensory information, context, and emotional salience. Recent techniques, such as optogenetic methods of circuit dissection, have made it possible to tease apart the contributions of individual circuit components. Here we review the synaptic properties of these main glutamatergic inputs to the rodent mPFC, how each is altered in animal models of chronic pain, and how these alterations contribute to pain-associated mPFC deactivation. By understanding the contributions of these individual circuit components, we strive to understand the broad spectrum of chronic pain and comorbid pathologies, how they are generated, and how they might be alleviated.

Dysregulation of the PI3K/Akt/mTOR signaling cascade has been associated with the pathology of neurodegenerative disorders, specifically Alzheimer's disease (AD). Both in-vivo models and post-mortem brain samples of individuals with AD have commonly shown hyperactivation of the pathway. In the present study, we examine how neuron subset-specific deletion of Pten (NS-Pten) in mice, which presents with hyperactive mammalian target of rapamycin (mTOR) activity, affects the hippocampal protein levels of key neuropathological hallmarks of AD. We found NS-Pten knockout (KO) mice to have elevated levels of amyloid-β, α-synuclein, neurofilament-L, and pGSK3α in the hippocampal synaptosome compared with NS-Pten wild type mice. In contrast, there was a decreased expression of amyloid precursor protein, tau, GSK3α, and GSK3β in NS-Pten KO hippocampi. Overall, there were significant alterations in levels of proteins associated with AD pathology in NS-Pten KO mice. This study provides novel insight into how altered mTOR signaling is linked to AD pathology, without the use of an in-vivo AD model that already displays neuropathological hallmarks of the disease.

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The purpose of this investigation was to examine cerebellar levels of several molecular signaling pathways, including PI3K/AKT/mTOR signaling and markers of neuronal migration, following loss of the Pten (phosphatase and tensin homolog) gene in a subset of neurons, as well as the accompanying behavior phenotype in mice. Motor coordination and learning were measured by the sticker removal task and the accelerating rotarod. Western blots were conducted on cerebellar tissue samples. We demonstrated that neuron-specific deletion of Pten (NS-Pten) in mice led to deficits in motor coordination. These changes were accompanied by alterations in many different proteins, including the PI3K/AKT/mTOR signaling pathway, FMRP, glutamate receptors and neuronal migration markers. These data firstly support a role for hyperactivation of mTOR in the cerebellum following loss of Pten, accompanied by behavioral deficits. Moreover, the results of the current study support a broader role for Pten signaling in early neuronal migration and organization of the cerebellum, and point to a putative role for Pten for many neuropsychiatric conditions.

Summary Objective Infant crying is a series of innate vocal patterns intended to elicit the attention of adult caregivers for fulfillment of specific needs, such as pain, hunger, or hypostimulation. It is one of the earliest forms of observable communication. In neonatal rodents, this behavior has recently been investigated as a potential early behavioral marker of neural deficits in neurodevelopmental disorders. However, few studies have examined the effects of seizures on vocalization behavior during the neonatal period. The purpose of this study is to investigate the effect of a single kainate-induced early life seizure on vocalization behavior in mice. This study also investigates the subsequent effect of seizures on two pathways critical for early neural development and epileptogenesis: the PI3K-Akt-mTOR and Canonical Wnt intracellular signaling pathways. Methods On postnatal day 10, male and female 129SvEvTac mice received a single intraperitoneal injection of kainic acid (2.5 mg/kg) or vehicle injection. The kainate administration resulted in 1–2 hours of status epilepticus. On postnatal days 11 and 12, the quantity and duration of isolation-induced ultrasonic vocalizations were recorded. Western blotting analyses were performed using male and female pups on postnatal day 12. Results There was significant, male-specific suppression in the quantity and total duration of 50-kHz calls on postnatal day 12 following seizures. The hippocampi of males on this postnatal day also revealed male specific changes in the PI3K-Akt-mTOR intracellular signaling pathway, as well as changes in phosphorylated fragile × mental retardation protein. Significance These findings demonstrate that early life seizures can disrupt communication behavior in neonatal mice.

The current study aimed to further address important questions regarding the therapeutic efficacy of omega-3 fatty acids for various behavioral and neuroimmune aspects of the Fmr1 phenotype. To address these questions, our experimental design utilized two different omega-3 fatty acid administration timepoints, compared to both standard laboratory chow controls (“Standard”) and a diet controlling for the increase in fat content (“Control Fat”). In the first paradigm, post-weaning supplementation (after postnatal day 21) with the omega-3 fatty acid diet (“Omega-3”) reversed deficits in startle threshold, but not deficits in prepulse inhibition, and the effect on startle threshold was not specific to the Omega-3 diet. However, post-weaning supplementation with both experimental diets also impaired acquisition of a fear response, recall of the fear memory and contextual fear conditioning compared to the Standard diet. The post-weaning Omega-3 diet reduced hippocampal expression of IL-6 and this reduction of IL-6 was significantly associated with diminished performance in the fear conditioning task. In the perinatal experimental paradigm, the Omega-3 diet attenuated hyperactivity and acquisition of a fear response. Additionally, perinatal exposure to the Control Fat diet (similar to a “Western” diet) further diminished nonsocial anxiety in the Fmr1 knockout. This study provides significant evidence that dietary fatty acids throughout the lifespan can significantly impact the behavioral and neuroimmune phenotype of the Fmr1 knockout model.