Transgenic rescue of phenotypic deficits in a mouse model of alternating hemiplegia of childhood

Missense mutations in ATP1A3 encoding Na+,K+-ATPase α3 are the primary cause of alternating hemiplegia of childhood (AHC). Most ATP1A3 mutations in AHC lie within a cluster in or near transmembrane α-helix TM6, including I810N that is also found in the Myshkin mouse model of AHC. These mutations all substantially reduce Na+,K+-ATPase α3 activity. Herein, we show that Myshkin mice carrying a wild-type Atp1a3 transgene that confers a 16 % increase in brain-specific total Na+,K+-ATPase activity show significant phenotypic improvements compared with non-transgenic Myshkin mice. Interventions to increase the activity of wild-type Na+,K+-ATPase α3 in AHC patients should be investigated further

Characterization of cognitive deficits in mice with an alternating hemiplegia-linked mutation

Cognitive impairment is a prominent feature in a range of different movement disorders. Children with Alternating Hemiplegia of Childhood are prone to developmental delay, with deficits in cognitive functioning becoming progressively more evident as they grow older. Heterozygous mutations of the ATP1A3 gene, encoding the Na+,K+-ATPase α3 subunit, have been identified as the primary cause of Alternating Hemiplegia. Heterozygous Myshkin mice have an amino acid change (I810N) in Na+,K+-ATPase α3 that is also found in Alternating Hemiplegia. To investigate whether Myshkin mice exhibit learning and memory deficits resembling the cognitive impairments of patients with Alternating Hemiplegia, we subjected them to a range of behavioral tests that interrogate various cognitive domains. Myshkin mice showed impairments in spatial memory, spatial habituation, locomotor habituation, object recognition, social recognition, and trace fear conditioning, as well as in the visible platform version of the Morris water maze. Increasing the duration of training ameliorated the deficit in social recognition but not in spatial habituation. The deficits of Myshkin mice in all of the learning and memory tests used are consistent with the cognitive impairment of the vast majority of AHC patients. These mice could thus help advance our understanding of the underlying neural mechanisms influencing cognitive impairment in patients with ATP1A3-related disorders

Missense mutation in DISC1 C-terminal coiled-coil has GSK3β signaling and sex-dependent behavioral effects in mice

Disrupted-in-Schizophrenia 1 (DISC1) is a risk factor for schizophrenia and affective disorders. The full-length DISC1 protein consists of an N-terminal ‘head’ domain and a C-terminal tail domain that contains several predicted coiled-coils, structural motifs involved in protein-protein interactions. To probe the in vivo effects of missense mutation of DISC1’s C-terminal tail, we tested mice carrying mutation D453G within a predicted α-helical coiled-coil region. We report that, relative to wild-type littermates, female DISC1D453G mice exhibited novelty-induced hyperlocomotion, an anxiogenic profile in the elevated plus-maze and open field tests, and reduced social exploration of unfamiliar mice. Male DISC1D453G mice displayed a deficit in passive avoidance, while neither males nor females exhibited any impairment in startle reactivity or prepulse inhibition. Whole brain homogenates showed normal levels of DISC1 protein, but decreased binding of DISC1 to GSK3β, decreased phospho-inhibition of GSK3β at serine 9, and decreased levels of β-catenin in DISC1D453G mice of either sex. Interrupted GSK3β signaling may thus be part of the mechanism underlying the behavioral phenotype associated with D453G, in common with the previously described N-terminal domain mutations Q31L and L100P in mice, and the schizophrenia risk-conferring variant R264Q in humans

Heterozygous deletion of α-neurexin I or α-neurexin II results in behaviors relevant to autism and schizophrenia

The neurexins are a family of presynaptic cell adhesion molecules. Human genetic studies have found heterozygous deletions affecting NRXN1 and NRXN2, encoding α-neurexin I (Nrxn1α) and α-neurexin II (Nrxn2α), in individuals with autism spectrum disorders and schizophrenia. However, the link between α-neurexin deficiency and the manifestation of psychiatric disorders remain unclear. To assess whether the heterozygous loss of neurexins results in behaviors relevant to autism or schizophrenia, we used mice with heterozygous (HET) deletion of Nrxn1α or Nrxn2α. We found that in a test of social approach, Nrxn1α HET mice show no social memory for familiar versus novel conspecifics. In a passive avoidance test, female Nrxn1α HET mice cross to the conditioned chamber sooner than female wild-type and Nrxn2α HET mice. Nrxn2α HET mice also express a lack of long-term object discrimination, indicating a deficit in cognition. The observed Nrxn1α and Nrxn2α genotypic effects were specific, as neither HET deletion had effects on a wide range of other behavioral measures, including several measures of anxiety. Our findings demonstrate that the heterozygous loss of α-neurexin I and α-neurexin II in mice leads to phenotypes relevant to autism and schizophrenia

Disc1 variation leads to specific alterations in adult neurogenesis

Disrupted in schizophrenia 1 (DISC1) is a risk factor for a spectrum of neuropsychiatric illnesses including schizophrenia, bipolar disorder, and major depressive disorder. Here we use two missense Disc1 mouse mutants, described previously with distinct behavioural phenotypes, to demonstrate that Disc1 variation exerts differing effects on the formation of newly generated neurons in the adult hippocampus. Disc1 mice carrying a homozygous Q31L mutation, and displaying depressive-like phenotypes, have fewer proliferating cells while Disc1 mice with a homozygous L100P mutation that induces schizophrenia-like phenotypes, show changes in the generation, placement and maturation of newly generated neurons in the hippocampal dentate gyrus. Our results demonstrate Disc1 allele specific effects in the adult hippocampus, and suggest that the divergence in behavioural phenotypes may in part stem from changes in specific cell populations in the brain

Deletion of α-neurexin II results in autism-related behaviors in mice

Autism is a common and frequently disabling neurodevelopmental disorder with a strong genetic basis. Human genetic studies have discovered mutations disrupting exons of the NRXN2 gene, which encodes the synaptic adhesion protein α-neurexin II (Nrxn2α), in two unrelated individuals with autism, but a causal link between NRXN2 and the disorder remains unclear. To begin to test the hypothesis that Nrxn2α deficiency contributes to the symptoms of autism, we employed Nrxn2α knockout (KO) mice that genetically model Nrxn2α deficiency in vivo. We report that Nrxn2α KO mice displayed deficits in sociability and social memory when exposed to novel conspecifics. In tests of exploratory activity, Nrxn2α KO mice displayed an anxiety-like phenotype in comparison with wild-type littermates, with thigmotaxis in an open field, less time spent in the open arms of an elevated plus maze, more time spent in the enclosure of an emergence test and less time spent exploring novel objects. However, Nrxn2α KO mice did not exhibit any obvious changes in prepulse inhibition or in passive avoidance learning. Real-time PCR analysis of the frontal cortex and hippocampus revealed significant decreases in the mRNA levels of genes encoding proteins involved in both excitatory and inhibitory transmission. Quantification of protein expression revealed that Munc18-1, encoded by Stxbp1, was significantly decreased in the hippocampus of Nrxn2α KO mice, which is suggestive of deficiencies in presynaptic vesicular release. Our findings demonstrate a causal role for the loss of Nrxn2α in the genesis of autism-related behaviors in mice

Relationships between psychotic and affective symptoms, schizotypal and dissociative phenomena, and adverse life events among individuals with psychotic disorders

Background: Psychotic symptoms and self-rated schizotypal phenomena have similar dimensional structures. Additionally, dissociative phenomena have conceptual links with psychosis/schizotypy and all of these phenotypes are associated with adverse life events (ALEs). The relationships between these factors among individuals with psychotic disorders are not well established and were investigated in this study. Method: 76 participants with any psychotic disorder were recruited from mental health services in West Yorkshire, UK. Lifetime psychotic and affective symptoms were assessed by research interviews and case record review. The self-rated Schizotypal Personality Questionnaire (SPQ) with additional questions regarding inappropriate affect, Dissociative Experiences Scale (DES), and questionnaires regarding cumulative adverse life events in childhood (CLEQ) and in the year before clinical onset (BLEQ) were also administered. Relationships between factors were assessed using Spearman correlations and linear regression analysis. Results: Correlations with relevant psychotic symptoms ranged from ~0.3 for some positive and negative SPQ subdomains to ~0 for disorganised subdomains. In contrast, SPQ and DES were highly correlated (~0.7). In univariate analysis, ALEs were associated with depression, DES, and positive and disorganised SPQ subdomains. In multivariable analysis, ALEs in childhood and before onset were independently associated with the SPQ Unusual perceptual experiences subdomain. Conclusion: Among individuals with psychotic disorders, neither SPQ nor DES questionnaire responses are likely to be useful proxies for psychotic symptoms. However, particularly questionnaire-based unusual perceptual experiences may be useful when assessing the range of phenomena associated with adverse life events

Distinct neurological disorders with ATP1A3 mutations

Mechanisms of disease, diagnostics and therap