Missense mutations in ATP1A3 encoding Na(+),K(+)-ATPaseα3 have been identified as the primary cause of alternating hemiplegia of childhood (AHC), a motor disorder with onset typically before the age of 6 months. Affected children tend to be of short stature and can also have epilepsy, ataxia and learning disability. The Na(+),K(+)-ATPase has a well-known role in maintaining electrochemical gradients across cell membranes, but our understanding of how the mutations cause AHC is limited. Myshkin mutant mice carry an amino acid change (I810N) that affects the same position in Na(+),K(+)-ATPase α3 as I810S found in AHC. Using molecular modelling, weshow that the Myshkin and AHC mutations display similarly severe structural impacts on Na(+),K(+)-ATPase α3, including upon the K(+) pore and predicted K(+) binding sites. Behavioural analysis of Myshkin mice revealed phenotypic abnormalities similar to symptoms of AHC, including motor dysfunctionand cognitive impairment. 2-DG imaging of Myshkin mice identified compromised thalamocortical functioning that includes a deficit in frontal cortex functioning (hypofrontality), directly mirroring that reported in AHC, along with reduced thalamocortical functional connectivity. Our results thus provide validation for missense mutations in Na(+),K(+)-ATPase α3 as a cause of AHC, and highlight Myshkin mice as a starting point for the exploration of disease mechanisms and novel treatments in AHC.
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Inbred mouse strains are widely used for genetic studies because of the isogenicity within a strain or F1 hybrid and the genetic heterogeneity between inbred strains. In the process of modifying Disc1 in the mouse genome, a 25-bp deletion was discovered in exon 6 of the gene in the 129S6/SvEvTac inbred strain, and subsequently in 16 other inbred strains in the category known as 'Castle's mice'. The deletion (Disc1(del)) induces a frame shift that introduces a premature termination codon, which has been shown to confer an impairment in working memory. To extend knowledge of the distribution of Disc1(del) among the various inbred strains of laboratory mouse, we investigated whether Disc1(del) is present in the categories known as 'Swiss mice' and 'strains derived from China and Japan'. We found that the FVB/NJ, SJL/J and SWR/J strains in the 'Swiss mice' category and DDY/JclSidSeyFrkJ in the 'China and Japan' category are homozygous for the Disc1(del) allele, while ICR/HaJ in the 'Swiss mice' category is homozygous for wild-type Disc1. Since the Disc1(del)-positive strains FVB and SJL are commonly used for the generation of transgenic mice, and thus contribute to the genetic background of multiple transgenic lines, our results may allow scientists to avoid the potential confounding effects of the Disc1(del) allele in transgenic studies of learning and memory.
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Schizophrenia and autistic spectrum disorder (ASD) are common, chronic mental conditions with both genetic and environmental components to their aetiology. The identification of genes influencing susceptibility to these disorders offers a rational route towards a clearer understanding of the neurobiology, and with this the prospect of treatment and prevention strategies tailored towards the remediation of the altered pathways. Copy number variants (CNVs) underlie many serious illnesses, including neurological and neurodevelopmental syndromes. Recent studies assessing copy number variation in ASD and schizophrenia have repeatedly observed heterozygous deletions eliminating exons of the neurexin-1α gene (but not the neurexin-1β gene) in patients with ASD and schizophrenia. The neurexins are synaptic adhesion proteins that are known to play a key role in synaptic formation and maintenance. The functional significance of the recurrent deletion is poorly understood, but the availability of mice with deletion of the promoter and first exon of neurexin-1α provides direct access to the biological effects of neurexin-1α disruption on phenotypes relevant to ASD and schizophrenia. We review the evidence for the role of neurexin-1α in schizophrenia and ASD, and consider how genetic disruption of neurexin-1α may underpin the neuropathology contributing to these distinct neurodevelopmental disorders.
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The basic helix-loop-helix PAS (Per, Arnt, Sim) domain transcription factor gene NPAS3 is a replicated genetic risk factor for psychiatric disorders. A knockout (KO) mouse model exhibits behavioral and adult neurogenesis deficits consistent with human illness. To define the location and mechanism of NPAS3 etiopathology, we combined immunofluorescent, transcriptomic and metabonomic approaches. Intense Npas3 immunoreactivity was observed in the hippocampal subgranular zone-the site of adult neurogenesis--but was restricted to maturing, rather than proliferating, neuronal precursor cells. Microarray analysis of a HEK293 cell line over-expressing NPAS3 showed that transcriptional targets varied according to circadian rhythm context and C-terminal deletion. The most highly up-regulated NPAS3 target gene, VGF, encodes secretory peptides with established roles in neurogenesis, depression and schizophrenia. VGF was just one of many NPAS3 target genes also regulated by the SOX family of transcription factors, suggesting an overlap in neurodevelopmental function. The parallel repression of multiple glycolysis genes by NPAS3 reveals a second role in the regulation of glucose metabolism. Comparison of wild-type and Npas3 KO metabolite composition using high-resolution mass spectrometry confirmed these transcriptional findings. KO brain tissue contained significantly altered levels of NAD(+), glycolysis metabolites (such as dihydroxyacetone phosphate and fructose-1,6-bisphosphate), pentose phosphate pathway components and Kreb's cycle intermediates (succinate andα-ketoglutarate). The dual neurodevelopmental and metabolic aspects of NPAS3 activity described here increase our understanding of mental illness etiology, and may provide a mechanism for innate and medication-induced susceptibility to diabetes commonly reported in psychiatric patients.
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Human trisomy 21 is the most frequent live-born human aneuploidy and causes a constellation of disease phenotypes classified as Down syndrome, which include heart defects, myeloproliferative disorder, cognitive disabilities and Alzheimer-type neurodegeneration. Because these phenotypes are associated with an extra copy of a human chromosome, the genetic analysis of Down syndrome has been a major challenge. To complement human genetic approaches, mouse models have been generated and analyzed based on evolutionary conservation between the human and mouse genomes. These efforts have been greatly facilitated by Cre/loxP-mediated mouse chromosome engineering, which may result in the establishment of minimal critical genomic regions and eventually new dosage-sensitive genes associated with Down syndrome phenotypes. The success in genetic analysis of Down syndrome will further enhance our understanding of this disorder and lead to better strategies in developing effective therapeutic interventions.
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The basic helix-loop-helix PAS (Per, Arnt, Sim) domain transcription factor gene NPAS3 is a replicated genetic risk factor for psychiatric disorders. A knockout (KO) mouse model exhibits behavioral and adult neurogenesis deficits consistent with human illness. To define the location and mechanism of NPAS3 etiopathology, we combined immunofluorescent, transcriptomic and metabonomic approaches. Intense Npas3 immunoreactivity was observed in the hippocampal subgranular zonethe site of adult neurogenesisbut was restricted to maturing, rather than proliferating, neuronal precursor cells. Microarray analysis of a HEK293 cell line over-expressing NPAS3 showed that transcriptional targets varied according to circadian rhythm context and C-terminal deletion. The most highly up-regulated NPAS3 target gene, VGF, encodes secretory peptides with established roles in neurogenesis, depression and schizophrenia. VGF was just one of many NPAS3 target genes also regulated by the SOX family of transcription factors, suggesting an overlap in neurodevelopmental function. The parallel repression of multiple glycolysis genes by NPAS3 reveals a second role in the regulation of glucose metabolism. Comparison of wild-type and Npas3 KO metabolite composition using high-resolution mass spectrometry confirmed these transcriptional findings. KO brain tissue contained significantly altered levels of NAD , glycolysis metabolites (such as dihydroxyacetone phosphate and fructose-1,6-bisphosphate), pentose phosphate pathway components and Kreb's cycle intermediates (succinate andα-ketoglutarate). The dual neurodevelopmental and metabolic aspects of NPAS3 activity described here increase our understanding of mental illness etiology, and may provide a mechanism for innate and medication-induced susceptibility to diabetes commonly reported in psychiatric patients. © 2012 Macmillan Publishers Limited All rights reserved.
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Myshkin mice heterozygous for an inactivating mutation in the neuron-specific Na(+) ,K(+) -ATPaseα3 isoform show behavior analogous to mania, including an abnormal endogenous circadian period. Agrin is a proteoglycan implicated as a regulator of synapses that has been proposed to inhibit activity of Na(+) ,K(+) -ATPase α3. We examined whether the mania-related behavior of Myshkin mice could be rescued by a reduction in the expression of agrin through genetic knockout. The suppression of agrin reduced hyperambulation and holeboard exploration, restored anxiety-like behavior (or reduced risk-taking behavior), improved prepulse inhibition and shortened the circadian period. Hence, agrin isimportant for regulating mania-like behavior and circadian rhythms. In Myshkin mice, the suppression of agrin increased brain Na(+) ,K(+) -ATPase activity by 11 ± 4%, whereas no effect on Na(+) ,K(+) -ATPase activity was detected when agrin was suppressed in mice without the Myshkin mutation. These results introduce agrin as a potential therapeutic target for the treatment of mania and other neurological disorders associated with reduced Na(+) ,K(+) -ATPase activity and neuronal hyperexcitability.
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Myshkin mice heterozygous for an inactivating mutation in the neuron-specific Na ,K -ATPaseα3 isoform show behavior analogous to mania, including an abnormal endogenous circadian period. Agrin is a proteoglycan implicated as a regulator of synapses that has been proposed to inhibit activity of Na ,K -ATPase α3. We examined whether the mania-related behavior of Myshkin mice could be rescued by a reduction in the expression of agrin through genetic knockout. The suppression of agrin reduced hyperambulation and holeboard exploration, restored anxiety-like behavior (or reduced risk-taking behavior), improved prepulse inhibition and shortened the circadian period. Hence, agrin is important for regulating mania-like behavior and circadian rhythms. In Myshkin mice, the suppression of agrin increased brain Na ,K -ATPase activity by 11 ± 4%, whereas no effect on Na,K -ATPase activity was detected when agrin was suppressed in mice without the Myshkin mutation. These results introduce agrin as a potential therapeutic target for the treatment of mania and other neurological disorders associated with reduced Na,K -ATPase activity and neuronal hyperexcitability. © 2012 The Authors. Genes, Brain and Behavior © 2012 Blackwell Publishing Ltd and International Behavioural and Neural Genetics Society.
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Human trisomy 21 is the most frequent live-born human aneuploidy and causes a constellation of disease phenotypes classified as Down syndrome, which include heart defects, myeloproliferative disorder, cognitive disabilities and Alzheimer-type neurodegeneration. Because these phenotypes are associated with an extra copy of a human chromosome, the genetic analysis of Down syndrome has been a major challenge. To complement human genetic approaches, mouse models have been generated and analyzed based on evolutionary conservation between the human and mouse genomes. These efforts have been greatly facilitated by Cre/loxP-mediated mouse chromosome engineering, which may result in the establishment of minimal critical genomic regions and eventually new dosagesensitive genes associated with Down syndrome phenotypes. The success in genetic analysis of Down syndrome will further enhance our understanding of this disorder and lead to better strategies in developing effective therapeutic interventions.© 2012 Landes Bioscience.
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The N-methyl-D-aspartate receptor (NMDAR), a major excitatory ligand-gated ion channel in the central nervous system (CNS), is a principal mediator of synaptic plasticity. Here we report that neuropilin tolloid-like 1 (Neto1), a complement C1r/C1s, Uegf, Bmp1 (CUB) domain-containing transmembrane protein, is a novel component of the NMDAR complex critical for maintaining the abundance of NR2A-containing NMDARs in the postsynaptic density. Neto1-null mice have depressed long-term potentiation (LTP) at Schaffer collateral-CA1 synapses, with the subunit dependency of LTP induction switching from the normal predominance of NR2A-to NR2B-NMDARs. NMDAR-dependent spatial learning and memory is depressed in Neto1-null mice, indicating that Neto1 regulates NMDA receptor-dependent synaptic plasticity and cognition. Remarkably, we also found that the deficits in LTP, learning, and memory in Neto1-null mice were rescued by the ampakine CX546 at doses without effect in wild-type. Together, our results establish the principle that auxiliary proteins are required for the normal abundance of NMDAR subunits at synapses, and demonstrate that an inherited learning defect can be rescued pharmacologically, a finding with therapeutic implications for humans.
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Swiss mice are among the most commonly used outbred strains in biomedical research. Because prior knowledge of the baseline phenotypes of mouse strains will allow informed selection of strains for particular experiments, we sought to characterize the behavior of two previously untested outbred Swiss strains--NIH Swiss and Black Swiss--in the two most widely used paradigms for evaluating the cognitive abilities of mice. Unlike the C57BL/6J and C57BL/6J-Tyr(c-2J) controls, animals of both outbred Swiss strains were unable to demonstrate learning in the Morris water maze and contextual fear conditioning paradigms. A polymerase chain reaction assay revealed that all of the NIH Swiss and Black Swiss mice tested were homozygous for the recessive retinal degeneration 1 mutation of the Pde6b gene. Histological examination of NIH Swiss and Black Swiss mouse eyes confirmed the presence of retinal degeneration, which causes visual image blindness. These findings indicate that NIH Swiss and Black Swiss mice are visually im paired and thus may be unsuitable for use in some experiments.
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The goal of the Complex Trait Consortium is to promote the development of resources that can be used to understand, treat and ultimately prevent pervasive human diseases. Existing and proposed mouse resources that are optimized to study the actions of isolated genetic loci on a fixed background are less effective for studying intact polygenic networks and interactions among genes, environments, pathogens and other factors. The Collaborative Cross will provide a common reference panel specifically designed for the integrative analysis of complex systems and will change the way we approach human health and disease.
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When paternally transmitted, two independent ENU-induced mutations showed reduced whole body wet weight soon after birth. The mutations were mapped to Chromosome 9 (Chr 9) between the markers D9Mit208 and D9Mit215. Their map position and imprinted status suggested that they might alter RAS protein-specific guanine nucleotide releasing factor 1 expression. Both mutations introduced premature chain termination codons into the coding sequence of Rasgrf1, and no Ras-GRF1 protein was detected in the brain. The GENA53 line had a C to T transition at nucleotide 2137, and the line GENA37 had a T to A transversion at nucleotide 3552 of the cDNA sequence. Mutant mice had near normal body weight at birth, but their weight started to lag behind that of wild-type littermates during the first week, and they were about 15% lighter as adults.
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We have previously reported the results of genome-wide searches in two murine F(2) populations for QTLs that influence survival following Trypanosoma congolense infection. Three loci, Tir1, Tir2, and Tir3, were identified and mapped to mouse Chromosomes (Chrs) 17, 5, and 1 respectively, with confidence intervals (CIs) in the range 10-40 cM. The size of these CIs is to a large degree the consequence of limited numbers of recombination events in small chromosomal regions in F(2) populations. A number of population designs have been proposed to increase recombination levels in crosses, one of which is the advanced intercross line (AIL). Here we report fine mapping of Tir1, Tir2, and Tir3 in G6 populations of two independent murine AILs created by crossing the C57BL/6J strain with the A/J and BALB/cJ strains, respectively. Data were analyzed by two methods that gave equally informative and similar results. The three QTLs were confirmed in the A/J x C57BL/6J AIL and in the combined data set, but Tir2 was apparently lost from the BALB/cJ x C57BL/6J AIL. The reduction in CIs for the Tir loci ranged from 2.5 to more than ten-fold in G6 populations by comparison with CIs obtained previously in the equivalent F(2) generations. Mapping in the AILs also resolved the Tir3 locus into three trypanosomiasis resistance QTLs, revealing a degree of complexity not evident in extensive studies at the F(2) level.
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