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Temporal lobe epilepsy is characterized by hippocampal neuronal death in CA1 and hilus. Dentate gyrus granule cells survive but show dispersion of the compact granule cell layer. This is associated with decrease of the glycoprotein Reelin, which regulates neuron migration and dendrite outgrow. Reelin-deficient (reeler) mice show no layering, their granule cells are dispersed throughout the dentate gyrus. We studied granule cell dendritic orientation and distribution of postsynaptic spines in reeler mice and two mouse models of temporal lobe epilepsy, namely the p35 knockout mice, which show Reelin-independent neuronal migration defects, and mice with unilateral intrahippocampal kainate injection. Granule cells were Golgi-stained and analyzed, using a computerized camera lucida system. Granule cells in naive controls exhibited a vertically oriented dendritic arbor with a small bifurcation angle if positioned proximal to the hilus and a wider dendritic bifurcation angle, if positioned distally. P35 knockout- and kainate-injected mice showed a dispersed granule cell layer, granule cells showed basal dendrites with wider bifurcation angles, which lost position-specific differences. Reeler mice lacked dendritic orientation. P35 knockout- and kainate-injected mice showed increased dendritic spine density in the granule cell layer. Molecular layer dendrites showed a reduced spine density in kainate-injected mice only, whereas in p35 knockouts no reduced spine density was seen. Reeler mice showed a homogenous high spine density. We hypothesize that granule cells migrate in temporal lobe epilepsy, develop new dendrites which show a spread of the dendritic tree, create new spines in areas proximal to mossy fiber sprouting, which is present in p35 knockout- and kainate-injected mice and loose spines on distal dendrites if mossy cell death is present, as it was in kainate-injected mice only. These results are in accordance with findings in epilepsy patients.

In 1981, I published a paper in the first issue of theJournal of Neurosciencewith my postdoctoral mentor, Alan Pearlman. It reported a quantitative analysis of the receptive field properties of neurons inreelermouse visual cortex and the surprising conclusion that although the neuronal somas were strikingly malpositioned, their receptive fields were unchanged. This suggested that in mouse cortex at least, neuronal circuits have very robust systems in place to ensure the proper formation of connections. This had the unintended consequence of transforming me from an electrophysiologist into a cellular and molecular neuroscientist who studied cell adhesion molecules and the molecular mechanisms they use to regulate axon growth. It took me a surprisingly long time to appreciate that your science is driven by the people around you and by the technologies that are locally available. As a professional puzzler, I like all different kinds of puzzles, but the most fun puzzles involve playing with other puzzlers. This is my story of learning how to find like-minded puzzlers to solve riddles about axon growth and regeneration.

The neocortex is composed of layers. Whether layers constitute an essential framework for the formation of functional circuits is not well understood. We investigated the brain-wide input connectivity of vasoactive intestinal polypeptide (VIP) expressing neurons in the reeler mouse. This mutant is characterized by a migration deficit of cortical neurons so that no layers are formed. Still, neurons retain their properties and reeler mice show little cognitive impairment. We focused on VIP neurons because they are known to receive strong long-range inputs and have a typical laminar bias toward upper layers. In reeler, these neurons are more dispersed across the cortex. We mapped the brain-wide inputs of VIP neurons in barrel cortex of wild-type and reeler mice with rabies virus tracing. Innervation by subcortical inputs was not altered in reeler, in contrast to the cortical circuitry. Numbers of long-range ipsilateral cortical inputs were reduced in reeler, while contralateral inputs were strongly increased. Reeler mice had more callosal projection neurons. Hence, the corpus callosum was larger in reeler as shown by structural imaging. We argue that, in the absence of cortical layers, circuits with subcortical structures are maintained but cortical neurons establish a different network that largely preserves cognitive functions.

Aims G protein‐activated inwardly rectifying potassium (GIRK) channels are related to rewarding effects of addictive drugs. The GIRK2 subunit is thought to play key roles in the reward system. Weaver mutant mice exhibit abnormal GIRK2 function and different behaviors that are caused by several addictive substances compared with wild‐type mice. However, mechanisms of reward‐related alterations in weaver mutant mice remain unclear. The present study investigated changes in the rewarding effects of methamphetamine (METH) in weaver mutant mice. Methods The rewarding effects of METH (4.0 mg/kg) were investigated using the conditioned place preference (CPP) paradigm. Extracellular dopamine level in the nucleus accumbens (NAc) was measured by in vivo microdialysis. To identify brain regions that were associated with these changes in rewarding effects, METH‐induced alterations of Fos expression were investigated by immunohistochemical analysis. Results Weaver mutant mice exhibited a significant decrease in METH‐induced CPP and dopamine release in the NAc. Methamphetamine significantly increased Fos expression in the posterior NAc (pNAc) shell in wild‐type but not in weaver mutant mice. Conclusions Methamphetamine did not induce rewarding effects in weaver mutant mice. The pNAc shell exhibited a significant difference in neuronal activity between wild‐type and weaver mutant mice. The present results suggest that the absence of METH‐induced CPP in weaver mutant mice is probably related to an innate reduction of dopamine and decreased neural activity in the pNAc shell that is partially attributable to the change of GIRK channel function. GIRK channels, especially those containing the GIRK2 subunit, appear to be involved in METH dependence., Methamphetamine did not induce rewarding effects in weaver mutant mice that possess a mutation in the GIRK2 subunit. The posterior nucleus accumbens shell exhibited a significant difference in neuronal activity between wild‐type and weaver mutant mice.

Aim A Japanese individual with schizophrenia harboring a novel exonic deletion in RELN was recently identified by genome-wide copy-number variation analysis. Thus, the present study aimed to generate and analyze a model mouse to clarify whether Reln deficiency is associated with the pathogenesis of schizophrenia. Methods A mouse line with a novel RELN exonic deletion (Reln-del) was established using the CRISPR/Cas9 method to elucidate the underlying molecular mechanism. Subsequently, general behavioral tests and histopathological examinations of the model mice were conducted and phenotypic analysis of the cerebellar granule cell migration was performed. Results The phenotype of homozygous Reln-del mice was similar to that of reeler mice with cerebellar atrophy, dysplasia of the cerebral layers, and abrogated protein levels of cerebral reelin. The expression of reelin in heterozygous Reln-del mice was approximately half of that in wild-type mice. Conversely, behavioral analyses in heterozygous Reln-del mice without cerebellar atrophy or dysplasia showed abnormal social novelty in the three-chamber social interaction test. In vitro reaggregation formation and neuronal migration were severely altered in the cerebellar cultures of homozygous Reln-del mice. Conclusion The present results in novel Reln-del mice modeled after our patient with a novel exonic deletion in RELN are expected to contribute to the development of reelin-based therapies for schizophrenia.

Krabbe's disease is an infantile neurodegenerative disease, which is affected by mutations in the lysosomal enzyme galactocerebrosidase, leading to the accumulation of its metabolite psychosine. We have shown previously that the S1P receptor agonist fingolimod (FTY720) attenuates psychosine-induced glial cell death and demyelination both in vitro and ex vivo models., Krabbe's disease is an infantile neurodegenerative disease, which is affected by mutations in the lysosomal enzyme galactocerebrosidase, leading to the accumulation of its metabolite psychosine. We have shown previously that the S1P receptor agonist fingolimod (FTY720) attenuates psychosine-induced glial cell death and demyelination both in vitro and ex vivo models. These data, together with a lack of therapies for Krabbe's disease, prompted the current preclinical study examining the effects of fingolimod in twitcher mice, a murine model of Krabbe's disease. Twitcher mice, both male and female, carrying a natural mutation in the galc gene were given fingolimod via drinking water (1 mg/kg/d). The direct impact of fingolimod administration was assessed via histochemical and biochemical analysis using markers of myelin, astrocytes, microglia, neurons, globoid cells, and immune cells. The effects of fingolimod on twitching behavior and life span were also demonstrated. Our results show that treatment of twitcher mice with fingolimod significantly rescued myelin levels compared with vehicle-treated animals and also regulated astrocyte and microglial reactivity. Furthermore, nonphosphorylated neurofilament levels were decreased, indicating neuroprotective and neurorestorative processes. These protective effects of fingolimod on twitcher mice brain pathology was reflected by an increased life span of fingolimod-treated twitcher mice. These in vivo findings corroborate initial in vitro studies and highlight the potential use of S1P receptors as drug targets for treatment of Krabbe's disease. SIGNIFICANCE STATEMENT This study demonstrates that the administration of the therapy known as fingolimod in a mouse model of Krabbe's disease (namely, the twitcher mouse model) significantly rescues myelin levels. Further, the drug fingolimod also regulates the reactivity of glial cells, astrocytes and microglia, in this mouse model. These protective effects of fingolimod result in an increased life span of twitcher mice.

10 páginas, 3 figuras. Contiene material suplementario accesible en: https://doi.org/10.1038/s41598-020-62050-7, Abnormalities in actin cytoskeleton have been linked to Friedreich's ataxia (FRDA), an inherited peripheral neuropathy characterised by an early loss of neurons in dorsal root ganglia (DRG) among other clinical symptoms. Despite all efforts to date, we still do not fully understand the molecular events that contribute to the lack of sensory neurons in FRDA. We studied the adult neuronal growth cone (GC) at the cellular and molecular level to decipher the connection between frataxin and actin cytoskeleton in DRG neurons of the well-characterised YG8R Friedreich's ataxia mouse model. Immunofluorescence studies in primary cultures of DRG from YG8R mice showed neurons with fewer and smaller GCs than controls, associated with an inhibition of neurite growth. In frataxin-deficient neurons, we also observed an increase in the filamentous (F)-actin/monomeric (G)-actin ratio (F/G-actin ratio) in axons and GCs linked to dysregulation of two crucial modulators of filamentous actin turnover, cofilin-1 and the actin-related protein (ARP) 2/3 complex. We show how the activation of cofilin is due to the increase in chronophin (CIN), a cofilin-activating phosphatase. Thus cofilin emerges, for the first time, as a link between frataxin deficiency and actin cytoskeleton alterations., Tis work was supported by grants from the Ministerio de Economía y Competitividad de España [Grant no. PI11/00678; SAF2015-66625-R] within the framework of the National R+ D+ I Plan and co-funded by the Instituto de Salud Carlos III (ISCIII)-Subdirección General de Evaluación y Fomento de la Investigación and FEDER funds; Fundación Ramón Areces (CIVP18A3899); the Generalitat Valenciana (ACOMP/2014/058; PROMETEO/2018/135). CIBERER is an initiative developed by the Instituto de Salud Carlos III in cooperative and translational research on rare diseases.

Background and purpose Mu and delta opioid receptors(MOP, DOP) contribution to the manifestations of pathological pain is not understood. We used genetic approaches to investigate the opioid mechanisms modulating neuropathic pain and its comorbid manifestations. Experimental approach We generated conditional knockout mice with MOP or DOP deletion in sensoryNav1.8-positive neurons (Nav1.8), in GABAergic forebrain neurons (DLX5/6) orconstitutively (CMV). Mutant mice and wild-type littermates were subjected topartial sciatic nerve ligation (PSNL) or sham surgery and their nociception wascompared. Anxiety-, depressivelike behaviour and cognitive performance were also measured. Opioid receptor mRNA expression, microgliosis and astrocytosis were assessed in the dorsalroot ganglia (DRG) and/or the spinal cord (SC). Key results Constitutive CMV-MOP knockouts after PSNL displayed reduced mechanical allodynia and enhanced heat hyperalgesia. This phenotype was accompanied by increased DOP expression in DRG and SC, and reduced microgliosis and astrocytosis in deep dorsal horn laminae. Conditional MOP knockouts and control mice developed similar hypersensitivity after PSNL, except for anenhanced heat hyperalgesia by DLX5/6-MOP male mice. Neuropathic pain-induced anxiety was aggravated in CMV-MOP and DLX5/6-MOP knockouts. Nerve-injured CMV-DOP mice showed increased mechanical allodynia, whereas Nav1.8-DOP and DLX5/8-DOP mice had partial nociceptive enhancement. CMV-DOP and DLX5/6-DOP mutants showed increased depressive-like behaviour after PSNL. Conclusions and implications MOP activity after nerve injury increased anxiety-like responses involving forebrain GABAergic neurons and enhanced mechanical pain sensitivity along with repression of DOP expression and spinal cord gliosis. In contrast, DOP shows a protective function limiting nociceptive and affective manifestations of neuropathic pain.

Rationale Psychotic disorders, such as schizophrenia, as well as some mood disorders, such as bipolar disorder, have been suggested to share common biological risk factors. One such factor is reelin, a large extracellular matrix glycoprotein that regulates neuronal migration during development as well as numerous activity-dependent processes in the adult brain. The current study sought to evaluate whether a history of stress exposure interacts with endogenous reelin levels to modify behavioural endophenotypes of relevance to psychotic and mood disorders. Methods Heterozygous Reeler Mice (HRM) and wildtype (WT) controls were treated with 50 mg/L of corticosterone (CORT) in their drinking water from 6 to 9 weeks of age, before undergoing behavioural testing in adulthood. We assessed methamphetamine-induced locomotor hyperactivity, prepulse inhibition (PPI) of acoustic startle, short-term spatial memory in the Y-maze, and depression-like behaviour in the Forced-Swim Test (FST). Results HRM genotype or CORT treatment did not affect methamphetamine-induced locomotor hyperactivity, a model of psychosis-like behaviour. At baseline, HRM showed decreased PPI at the commonly used 100 msec interstimulus interval (ISI), but not at the 30 msec ISI or following challenge with apomorphine. A history of CORT exposure potentiated immobility in the FST amongst HRM, but not WT mice. In the Y-maze, chronic CORT treatment decreased novel arm preference amongst HRM, reflecting reduced short-term spatial memory. Conclusion These data confirm a significant role of endogenous reelin levels on stress-related behaviour, supporting a possible role in both bipolar disorder and schizophrenia. However, an interaction of reelin deficiency with dopaminergic regulation of psychosis-like behaviour remains unclear.

The intestinal barrier is composed of a complex cell network defining highly compartmentalized and specialized structures. Here, we use spatial transcriptomics to define how the transcriptomic landscape is spatially organized in the steady state and healing murine colon. At steady state conditions, we demonstrate a previously unappreciated molecular regionalization of the colon, which dramatically changes during mucosal healing. Here, we identified spatially-organized transcriptional programs defining compartmentalized mucosal healing, and regions with dominant wired pathways. Furthermore, we showed that decreased p53 activation defined areas with increased presence of proliferating epithelial stem cells. Finally, we mapped transcriptomics modules associated with human diseases demonstrating the translational potential of our dataset. Overall, we provide a publicly available resource defining principles of transcriptomic regionalization of the colon during mucosal healing and a framework to develop and progress further hypotheses.

Peripheral administration (oral, intranasal, intraperitoneal, intravenous) of assembled A53T α-synuclein induced synucleinopathy in heterozygous mice transgenic for human mutant A53T α-synuclein (line M83). The same was the case when cerebellar extracts from a case of multiple system atrophy with type II α-synuclein filaments were administered intraperitoneally, intravenously or intramuscularly. We observed abundant immunoreactivity for pS129 α-synuclein in nerve cells and severe motor impairment, resulting in hindlimb paralysis and shortened lifespan. Filaments immunoreactive for pS129 α-synuclein were in evidence. A 70% loss of motor neurons was present five months after an intraperitoneal injection of assembled A53T α-synuclein or cerebellar extract with type II α-synuclein filaments from an individual with a neuropathologically confirmed diagnosis of multiple system atrophy. Microglial cells changed from a predominantly ramified to a dystrophic appearance. Taken together, these findings establish a close relationship between the formation of α-synuclein inclusions in nerve cells and neurodegeneration, accompanied by a shift in microglial cell morphology. Propagation of α-synuclein inclusions depended on the characteristics of both seeds and transgenically expressed protein. Supplementary Information The online version contains supplementary material available at 10.1186/s40478-021-01291-7.

The BTBR T + Itpr3tf/J (BTBR) mouse has developmental disorders in the central nervous system and many aberrant neuroanatomical structures. However, identification of the pathological mechanisms underlying these abnormal neuroanatomical structures in the brains of BTBR mice is still lacking. Posttranslational modifications (PTMs) are known to be involved in the regulation of diverse cellular processes, and evidence shows that some types of PTMs are associated with the development of the central nervous system. In this study, we detected four novel PTMs in the cerebral cortex of BTBR mice as compared to C57BL/6 J (B6) mice using western blotting. Results revealed that lysine crotonylation and succinylation were elevated in the cerebral cortex of BTBR mice compared to levels in B6 mice. We speculate that elevated profiles of lysine crotonylation and succinylation may be involved in mechanisms related to neuroanatomical abnormalities in cerebral cortex of BTBR mice.

Glycolysis and mitochondrial respiration are essential for oligodendrocyte metabolism in both the developing and adult CNS. Based on recent reports on the effects of the proinflammatory cytokine IFN-γ on metabolism and on oligodendrocytes, we addressed whether IFN-γ may affect oligodendrocyte bioenergetics in ways relevant to CNS disease. Oligodendrocytes of mice treated with IFN-γ showed significant reductions in aerobic glycolysis and mitochondrial respiration. As expected, IFN-γ treatment led to the induction of STAT1 in oligodendrocytes indicating active signaling into these cells. To determine the direct effects of IFN-γ on oligodendrocyte metabolism, cultured oligodendrocytes were treated with IFN-γ in vitro, which resulted in suppression of glycolysis similar to oligodendrocytes of animals treated with IFN-γ in vivo. Mice lacking SHP-1, a key regulator of IFN-γ and STAT1 signaling in CNS glia, had high constitutive levels of STAT1 and decreased aerobic glycolysis and mitochondrial respiration rates relative to wild type mouse oligodendrocytes. Together, these data show that IFN-γ and SHP-1 control oligodendrocyte bioenergetics in ways that may relate to the role of this cytokine in CNS disease.

Neuropathic pain is a significant public health challenge, yet the underlying mechanisms remain poorly understood. Painful small fiber neuropathy (SFN) may be caused by gain-of-function mutations in Nav1.8, a sodium channel subtype predominantly expressed in peripheral nociceptive neurons. However, it is not clear how Nav1.8 disease mutations induce sensory neuron hyperexcitability. Here we studied two mutations in Nav1.8 associated with hypersensitive sensory neurons: G1662S reported in painful SFN; and T790A, which underlies increased pain behaviors in thePossumtransgenic mouse strain. We show that, in male DRG neurons, these mutations, which impair inactivation, significantly increase TTX-resistant resurgent sodium currents mediated by Nav1.8. The G1662S mutation doubled resurgent currents, and the T790A mutation increased them fourfold. These unusual currents are typically evoked during the repolarization phase of action potentials. We show that the T790A mutation greatly enhances DRG neuron excitability by reducing current threshold and increasing firing frequency. Interestingly, the mutation endows DRG neurons with multiple early afterdepolarizations and leads to substantial prolongation of action potential duration. In DRG neurons, siRNA knockdown of sodium channel β4 subunits fails to significantly alter T790A current density but reduces TTX-resistant resurgent currents by 56%. Furthermore, DRG neurons expressing T790A channels exhibited reduced excitability with fewer early afterdepolarizations and narrower action potentials after β4 knockdown. Together, our data demonstrate that open-channel block of TTX-resistant currents, enhanced by gain-of-function mutations in Nav1.8, can make major contributions to the hyperexcitability of nociceptive neurons, likely leading to altered sensory phenotypes including neuropathic pain in SFN.SIGNIFICANCE STATEMENTThis work demonstrates that two disease mutations in the voltage-gated sodium channel Nav1.8 that induce nociceptor hyperexcitability increase resurgent currents. Nav1.8 is crucial for pain sensations. Because resurgent currents are evoked during action potential repolarization, they can be crucial regulators of action potential activity. Our data indicate that increased Nav1.8 resurgent currents in DRG neurons greatly prolong action potential duration and enhance repetitive firing. We propose that Nav1.8 open-channel block is a major factor in Nav1.8-associated pain mechanisms and that targeting the molecular mechanism underlying these unique resurgent currents represents a novel therapeutic target for the treatment of aberrant pain sensations.

Cannabis use is widespread among adolescents and has been associated with long-term negative outcomes on neurocognitive functions. However, the factors that contribute to the long-term detrimental effects of cannabis use remain poorly understood. Here, we studied how Reelin deficiency influences the behavior of mice exposed to cannabis during adolescence. Reelin is a gene implicated in the development of the brain and of psychiatric disorders. To this aim, heterozygous Reeler (HR) mice, that express reduced level of Reelin, were chronically injected during adolescence with high doses (10 mg/kg) of Δ9-tetrahydrocannabinol (THC), a major psychoactive component of cannabis. Two weeks after the last injection of THC, mice were tested with multiple behavioral assays, including working memory, social interaction, locomotor activity, anxiety-like responses, stress reactivity, and pre-pulse inhibition. Compared to wild-type (WT), HR mice treated with THC showed impaired social behaviors, elevated disinhibitory phenotypes and increased reactivity to aversive situations, in a sex-specific manner. Overall, these findings show that Reelin deficiency influences behavioral abnormalities caused by heavy consumption of THC during adolescence and suggest that elucidating Reelin signaling will improve our understanding of neurobiological mechanisms underlying behavioral traits relevant to the development of psychiatric conditions.

Anxiety-related behaviors in mice are often assessed over short periods starting immediately after introducing the animals in a dedicated apparatus. In these usual conditions (5−10 min periods), the cerebellar Lurcher mutants showed disinhibited behaviors characterized by abnormally high exploration of the aversive areas in the elevated plus-maze test. We nevertheless observed that this disinhibition sharply weakened after 10 min. We therefore decided to further investigate the influence of the disinhibition on the intrinsic and anxiety-related exploratory behaviors in Lurcher mice, with a special focus on familiarization effects. To this end, we used an innovative apparatus, the Dual Maze, permitting to tune the familiarization level of animals to the experimental context before they are faced with more (open configuration of the device) or less (closed configuration of the device) aversive areas. Chlordiazepoxide administration in BALB/c mice in a preliminary experiment confirmed both the face and the predictive validity of our device as anxiety test and its ability to measure exploratory motivation. The results obtained with the Lurcher mice in the open configuration revealed that 20 min of familiarization to the experimental context abolished the behavioral abnormalities they exhibited when not familiarized with it. In addition, their exploratory motivation, as measured in the closed configuration, was comparable to that of their non-mutant littermates, whatever the level of familiarization applied. Exemplifying the interest of this innovative device, the results we obtained in the Lurcher mutants permitted to differentiate between the roles played by the cerebellum in exploratory motivation and stress-related behaviors.

Patients with neurodevelopmental disorders show impaired motor skill learning. It is unclear how the effect of genetic variation on synaptic function and transcriptome profile may underlie experience-dependent cortical plasticity, which supports the development of fine motor skills. RELN (reelin) is one of the genes implicated in neurodevelopmental psychiatric vulnerability. Heterozygous reeler mutant (HRM) mice displayed impairments in reach-to-grasp learning, accompanied by less extensive cortical map reorganization compared with wild-type mice, examined after 10 days of training by intracortical microstimulation. Assessed by patch-clamp recordings after 3 days of training, the training induced synaptic potentiation and increased glutamatergic-transmission of cortical layer III pyramidal neurons in wild-type mice. In contrast, the basal excitatory and inhibitory synaptic functions were depressed, affected both by presynaptic and postsynaptic impairments in HRM mice; and thus, no further training-induced synaptic plasticity occurred. HRM exhibited downregulations of cortical synaptophysin, immediate-early gene expressions, and gene enrichment, in response to 3 days of training compared with trained wild-type mice, shown using quantitative reverse transcription polymerase chain reaction, immunohistochemisty, and RNA-sequencing. We demonstrated that motor learning impairments associated with modified experience-dependent cortical plasticity are at least partially attributed by the basal synaptic alternation as well as the aberrant early experience-induced gene enrichment in HRM.

Exercise therapy represents an important tool for the treatment of many neurological diseases, including cerebellar degenerations. In mouse models, exercise may decelerate the progression of gradual cerebellar degeneration via potent activation of neuroprotective pathways. However, whether exercise could also improve the condition in mice with already heavily damaged cerebella remains an open question. Here we aimed to explore this possibility, employing a mouse model with dramatic early-onset cerebellar degeneration, the Lurcher mice. The potential of forced physical activity and environmental enrichment (with the possibility of voluntary running) for improvement of behaviour and neuroplasticity was evaluated by a series of behavioural tests, measuring BDNF levels and using stereological histology techniques. Using advanced statistical analysis, we showed that while forced physical activity improved motor learning by ∼26 % in Lurcher mice and boosted BDNF levels in the diseased cerebellum by 57 %, an enriched environment partially alleviated some behavioural deficits related to behavioural disinhibition. Specifically, Lurcher mice exposed to the enriched environment evinced reduced open arm exploration in elevated plus maze test by 18 % and increased immobility almost 9-fold in the forced swim test. However, we must conclude that the overall beneficial effects were very mild and much less clear, compared to previously demonstrated effects in slowly-progressing cerebellar degenerations.

Heterogeneous nuclear ribonuclear protein l-like (hnRNPLL) is an RNA binding protein that regulates alternative splicing of mRNA and is abundantly expressed in memory T lymphocytes of the immune system and in the brain. A hypomorphic allele of the gene encoding hnRNPLL (Hnrpllthunder) selectively reduces T cell accumulation in lymphoid tissues, but little is known about its effects in the brain. Therefore, we exposed Hnrpllthunder mice to a test battery with relevance for a range of psychiatric illnesses. Thunder mice showed enhanced immobility in the tail-suspension test for depression-related behaviours, impaired short-term spatial memory in the Y-maze and reduced avoidance learning in the active avoidance test. Thus, in addition to its reported effects on immune function, the hnRNPLL mutation in thunder mice selectively affected aspects of behaviour.

Comprehensive analysis of neuronal networks requires brain-wide measurement of connectivity, activity, and gene expression. Although high-throughput methods are available for mapping brain-wide activity and transcriptomes, comparable methods for mapping region-to-region connectivity remain slow and expensive because they require averaging across hundreds of brains. Here we describe BRICseq (brain-wide individual animal connectome sequencing), which leverages DNA barcoding and sequencing to map connectivity from single individuals in a few weeks and at low cost. Applying BRICseq to the mouse neocortex, we find that region-to-region connectivity provides a simple bridge relating transcriptome to activity: the spatial expression patterns of a few genes predict region-to-region connectivity, and connectivity predicts activity correlations. We also exploited BRICseq to map the mutant BTBR mouse brain, which lacks a corpus callosum, and recapitulated its known connectopathies. BRICseq allows individual laboratories to compare how age, sex, environment, genetics, and species affect neuronal wiring and to integrate these with functional activity and gene expression.

Objective Neurodegeneration and hair pigmentation alterations in mice occur consequent to aberrations at the Atrn locus coding for the transmembrane form of attractin. Earlier results pointed to a possible involvement in intracellular trafficking/export of secretory vesicles containing proteoglycan. Here we examined kidney and liver, both heavily dependent upon proteoglycan, of attractin-deficient mice to determine whether abnormalities were observed in these tissues. Results Histological and histochemical analysis to detect glycosylated protein identified a severe loss in attractin-deficient mice of extracellular proteoglycan between kidney tubules in addition to a loss of glycosylated material within the intratubular brush border. In the liver, extracellular matrix material was significantly depleted between hepatocytes together with swollen sinuses and aberrations in the proteoglycan-dependent space of Disse. These results are consistent with a generalized defect in extracellular proteoglycan deposition in Atrn-mutant mice and support previous reports suggesting a role for attractin in the secretory vesicle pathway.

Autism spectrum disorder (ASD) is a group of developmental pathologies that impair social communication and cause repetitive behaviors. The suggested roles of noncoding RNAs in pathology led us to perform a comparative analysis of the microRNAs expressed in the serum of human ASD patients. The analysis of a cohort of 45 children with ASD revealed that six microRNAs (miR-19a-3p, miR-361-5p, miR-3613-3p, miR-150-5p, miR-126-3p, and miR-499a-5p) were expressed at low to very low levels compared to those in healthy controls. A similar but less pronounced decrease was registered in the clinically unaffected parents of the sick children and in their siblings but never in any genetically unrelated control. Results consistent with these observations were obtained in the blood, hypothalamus and sperm of two of the established mouse models of ASD: valproic acid-treated animals and Cc2d1a+/− heterozygotes. In both instances, the same characteristic miRNA profile was evidenced in the affected individuals and inherited together with disease symptoms in the progeny of crosses with healthy animals. The consistent association of these genetic regulatory changes with the disease provides a starting point for evaluating the changes in the activity of the target genes and, thus, the underlying mechanism(s). From the applied societal and medical perspectives, once properly confirmed in large cohorts, these observations provide tools for the very early identification of affected children and progenitors.

Reelin has been implicated in the development of schizophrenia but the mechanisms involved in this interaction remain unclear. Chronic methamphetamine (Meth) use may cause dopaminergic sensitisation and psychosis and has been proposed to affect brain dopamine systems similarly to changes seen in schizophrenia. We compared the long-term effect of chronic Meth treatment between heterozygous reelin mice (HRM) and wildtype controls (WT) with the aim of better understanding the role of reelin in schizophrenia. Meth pretreatment induced sensitisation to the effect of an acute Meth challenge on locomotor activity, but it had no effect on baseline PPI or sociability and social preference. In all behavioural models, HRM did not significantly differ from WT at baseline, except spontaneous exploratory locomotor activity which was higher in HRM than WT, and sociability which was enhanced in HRM. Locomotor hyperactivity sensitisation was not significantly different between HRM and WT. Chronic Meth treatment reduced spontaneous locomotor activity to the level of WT. No deficits in PPI or social behaviour were induced by chronic Meth pretreatment in either strain. In conclusion, these data do not support a role of reelin in schizophrenia, at least not in HRM and in the methamphetamine sensitisation model.

Numerous mutations that impair retrograde membrane trafficking between endosomes and the Golgi apparatus lead to neurodegenerative diseases. For example, mutations in the endosomal retromer complex are implicated in Alzheimer’s and Parkinson’s diseases, and mutations of the Golgi-associated retrograde protein (GARP) complex cause progressive cerebello-cerebral atrophy type 2 (PCCA2). However, how these mutations cause neurodegeneration is unknown. GARP mutations in yeast, including one causing PCCA2, result in sphingolipid abnormalities and impaired cell growth that are corrected by treatment with myriocin, a sphingolipid synthesis inhibitor, suggesting that alterations in sphingolipid metabolism contribute to cell dysfunction and death. Here we tested this hypothesis in wobbler mice, a murine model with a homozygous partial loss-of-function mutation in Vps54 (GARP protein) that causes motor neuron disease. Cytotoxic sphingoid long-chain bases accumulated in embryonic fibroblasts and spinal cords from wobbler mice. Remarkably, chronic treatment of wobbler mice with myriocin markedly improved their wellness scores, grip strength, neuropathology, and survival. Proteomic analyses of wobbler fibroblasts revealed extensive missorting of lysosomal proteins, including sphingolipid catabolism enzymes, to the Golgi compartment, which may contribute to the sphingolipid abnormalities. Our findings establish that altered sphingolipid metabolism due to GARP mutations contributes to neurodegeneration and suggest that inhibiting sphingolipid synthesis might provide a useful strategy for treating these disorders.

Previously, we revealed that brain Ang-(1-7) deficiency was involved in the pathogenesis of sporadic Alzheimer's disease (AD). We speculated that restoration of brain Ang-(1-7) levels might have a therapeutic effect against AD. However, the relatively short duration of biological effect limited the application of Ang-(1-7) in animal experiments. Since Ang-(1-7) is generated by its metabolic enzyme ACE2, we then tested the efficacy of an ACE2 activator diminazene aceturate (DIZE) on AD-like neuropathology and cognitive impairment in senescence-accelerated mouse prone substrain 8 (SAMP8) mice, an animal model of sporadic AD. Eight-month-old SAMP8 mice were injected intraperitoneally with vehicle or DIZE once a day for 30 consecutive days. DIZE markedly elevated brain Ang-(1-7) and MAS1 levels. Meanwhile, DIZE significantly reduced the levels of Aβ1-42, hyperphosphorylated tau and pro-inflammatory cytokines in the brain. The synaptic and neuronal losses in the brain were ameliorated by DIZE. Importantly, DIZE improved spatial cognitive functions in the Morris water maze test. In conclusion, this study demonstrates that DIZE ameliorates AD-like neuropathology and rescues cognitive impairment in SAMP8 mice. These beneficial effects of DIZE may be achieved by activating brain ACE2/Ang-(1-7)/MAS1 axis. These findings highlight brain ACE2/Ang-(1-7)/MAS1 axis as a potential target for the treatment of sporadic AD.

Several spontaneous mouse mutants with deficits in motor coordination and associated cerebellar neuropathology have been described. Intriguingly, both visible gait alterations and neuroanatomical abnormalities throughout the brain differ across mutants. We previously used the LocoMouse system to quantify specific deficits in locomotor coordination in mildly ataxic Purkinje cell degeneration mice (pcd; Machado et al., 2015). Here, we analyze the locomotor behavior of severely ataxic reeler mutants and compare and contrast it with that of pcd. Despite clearly visible gait differences, direct comparison of locomotor kinematics and linear discriminant analysis reveal a surprisingly similar pattern of impairments in multijoint, interlimb, and whole-body coordination in the two mutants. These findings capture both shared and specific signatures of gait ataxia and provide a quantitative foundation for mapping specific locomotor impairments onto distinct neuropathologies in mice.

In humans, the majority of sustained traumatic brain injuries (TBIs) are classified as 'mild' and most often a result of a closed head injury (CHI). The effects of a non-penetrating CHI are not benign and may lead to chronic pathology and behavioral dysfunction, which could be worsened by repeated head injury. Clinical-neuropathological correlation studies provide evidence that conversion of tau into abnormally phosphorylated proteotoxic intermediates (p-tau) could be part of the pathophysiology triggered by a single TBI and enhanced by repeated TBIs. However, the link between p-tau and CHI in rodents remains controversial. To address this question experimentally, we induced a single CHI or two CHIs to WT or rTg4510 mice. We found that 2× CHI increased tau phosphorylation in WT mice and rTg4510 mice. Behavioral characterization in WT mice found chronic deficits in the radial arm water maze in 2× CHI mice that had partially resolved in the 1× CHI mice. Moreover, using Manganese-Enhanced Magnetic Resonance Imaging with R1 mapping - a novel functional neuroimaging technique - we found greater deficits in the rTg4510 mice following 2× CHI compared to 1× CHI. To integrate our findings with prior work in the field, we conducted a systematic review of rodent mild repetitive CHI studies. Following Prisma guidelines, we identified 25 original peer-reviewed papers. Results from our experiments, as well as our systematic review, provide compelling evidence that tau phosphorylation is modified by experimental mild TBI studies; however, changes in p-tau levels are not universally reported. Together, our results provide evidence that repetitive TBIs can result in worse and more persistent neurological deficits compared to a single TBI, but the direct link between the worsened outcome and elevated p-tau could not be established.

Synapses are key structural determinants for information processing and computations in the normal and pathologically altered brain. Here, the quantitative morphology of excitatory synaptic boutons in the “reeler” mutant, a model system for various neurological disorders, was investigated and compared with wild-type (WT) mice using high-resolution, fine-scale electron microscopy (EM) and quantitative three-dimensional (3D) models of synaptic boutons. Beside their overall geometry, the shape and size of presynaptic active zones (PreAZs) and postsynaptic densities (PSDs) forming the active zones and the three pools of synaptic vesicles (SVs), namely the readily releasable pool (RRP), the recycling pool (RP), and the resting pool, were quantified. Although the reeler mouse neocortex is severely disturbed, no significant differences were found in most of the structural parameters investigated: the size of boutons (~3 μm2), size of the PreAZs and PSDs (~0.17 μm2), total number of SVs, and SVs within a perimeter (p) of 10 nm and p20 nm RRP; the p60 nm, p100 nm, and p60–p200 nm RP; and the resting pool, except the synaptic cleft width. Taken together, the synaptic organization and structural composition of synaptic boutons in the reeler neocortex remain comparably “normal” and may thus contribute to a “correct” wiring of neurons within the reeler cortical network.

Cerebellar ataxias are severe neurodegenerative disorders with an early onset and progressive and inexorable course of the disease. Here, we report a single point mutation in the gene encoding Elongator complex subunit 6 causing Purkinje neuron degeneration and an ataxia-like phenotype in the mutant wobbly mouse. This mutation destabilizes the complex and compromises its function in translation regulation, leading to protein misfolding, proteotoxic stress, and eventual neuronal death. In addition, we show that substantial microgliosis is triggered by the NLRP3 inflammasome pathway in the cerebellum and that blocking NLRP3 function in vivo significantly delays neuronal degeneration and the onset of ataxia in mutant animals. Our data provide a mechanistic insight into the pathophysiology of a cerebellar ataxia caused by an Elongator mutation, substantiating the increasing body of evidence that alterations of this complex are broadly implicated in the onset of a number of diverse neurological disorders., Elp6 is a component of the Elongator complex that regulates tRNAs and translation. Here the authors identify a mutation in the Elp6 gene that contributes to the cerebellar ataxia-like phenotype in a mutant mouse.

Wobbler mice are experimental models for amyotrophic lateral sclerosis. As such they show motoneuron degeneration, motor deficits, and astrogliosis and microgliosis of the spinal cord. Additionally, Wobbler mice show increased plasma, spinal cord and brain corticosterone levels and focal adrenocortical hyperplasia, suggesting a pathogenic role for glucocorticoids in this disorder. Considering this endocrine background, we examined whether the glucocorticoid receptor (GR) modulator CORT 113176 prevents spinal cord neuropathology of Wobblers. CORT 113176 shows high affinity for the GR, with low or null affinity for other steroid receptors. We employed five-month-old genotyped Wobbler mice that received s.c. vehicle or 30 mg/kg/day for 4 days of CORT 113176 dissolved in sesame oil. The mice were used on the 4th day, 2 h after the last dose of CORT 113176. Vehicle-treated Wobbler mice presented vacuolated motoneurons, increased glial fibrillary acidic protein (GFAP)+ astrocytes and decreased glutamine synthase (GS)+ cells. There was strong neuroinflammation, shown by increased staining for IBA1+ microglia and CD11b mRNA, enhanced expression of tumor necrosis factor-α, its cognate receptor TNFR1, toll-like receptor 4, the inducible nitric oxide synthase, NFkB and the high-mobility group box 1 protein (HMGB1). Treatment of Wobbler mice with CORT 113176 reversed the abnormalities of motoneurons and down-regulated proinflammatory mediators and glial reactivity. Expression of glutamate transporters GLT1 and GLAST mRNAs and GLT1 protein was significantly enhanced over untreated Wobblers. In summary, antagonism of GR with CORT 113176 prevented neuropathology and showed anti-inflammatory and anti-glutamatergic effects in the spinal cord of Wobbler mice. Fil: Meyer, Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; Argentina Fil: Lara, Agustina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; Argentina Fil: Hunt, Hazel. CORCEPT Therapeutic; Estados Unidos Fil: Belanoff, Joseph. CORCEPT Therapeutic; Estados Unidos Fil: de Kloe, Ronald E.. Leiden University; Países Bajos Fil: Gonzalez Deniselle, Maria Claudia. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; Argentina. Universidad de Buenos Aires. Facultad de Medicina. Departamento de Bioquímica Humana; Argentina Fil: de Nicola, Alejandro Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; Argentina. Universidad de Buenos Aires. Facultad de Medicina. Departamento de Bioquímica Humana; Argentina

Cilia of olfactory sensory neurons (OSNs) are the primary site of odor binding; hence, their loss results in anosmia, a clinical manifestation of pleiotropic ciliopathies for which there are no curative therapies. We used OSN-specific Ift88 knock-out mice (Ift88(osnKO)) of both sexes to examine the mechanisms of ciliopathy-induced olfactory dysfunction and the potential for gene replacement to rescue odorant detection, restore olfactory circuitry, and restore odor-guided behaviors. Loss of OSN cilia in Ift88(osnKO) mice resulted in substantially reduced odor detection and odor-driven synaptic activity in the olfactory bulb (OB). Defects in OSN axon targeting to the OB were also observed in parallel with aberrant odor-guided behavior. Intranasal gene delivery of wild-type IFT88 to Ift88(osnKO) mice rescued OSN ciliation and peripheral olfactory function. Importantly, this recovery of sensory input in a limited number of mature OSNs was sufficient to restore axonal targeting in the OB of juvenile mice, and with delayed onset in adult mice. In addition, restoration of sensory input re-established course odor-guided behaviors. These findings highlight the spare capacity of the olfactory epithelium and the plasticity of primary synaptic input into the central olfactory system. The restoration of peripheral and central neuronal function supports the potential for treatment of ciliopathy-related anosmia using gene therapy. SIGNIFICANCE STATEMENT Ciliopathies, for which there are no curative therapies, are genetic disorders that alter cilia morphology and/or function in numerous tissue types, including the olfactory system, leading to sensory dysfunction. We show that in vivo intranasal gene delivery restores peripheral olfactory function in a ciliopathy mouse model, including axonal targeting in the juvenile and adult olfactory bulb. Gene therapy also demonstrated restoration of olfactory perception by rescuing odor-guided behaviors. Understanding the therapeutic window and viability for gene therapy to restore odor detection and perception may facilitate translation of therapies to ciliopathy patients with olfactory dysfunctions.

Classical eyeblink conditioning is an experimental model widely used for the study of the neuronal mechanisms underlying the acquisition of new motor and cognitive skills. There are two principal interpretations of the role of the cerebellum in the learning of eyelid conditioned responses (CRs). One considers that the cerebellum is the place where this learning is acquired and stored, while the second suggests that the cerebellum is mostly involved in the proper performance of acquired CRs, implying that there must be other brain areas involved in the learning process. We checked the timing of cerebellar interpositus nucleus (IPN) neurons’ firing rate with eyelid CRs in both wild-type (WT) and Lurcher (a model of cerebellar cortex degeneration) mice. We used delay and trace conditioning paradigms. WT mice presented a better execution for delay vs. trace conditioning and also for these two paradigms than did Lurcher mice. IPN neurons were activated during CRs following the activation of the orbicularis oculi muscle. Firing patterns of IPN neurons were altered in Lurcher mice. In conclusion, the cerebellum seems to be mostly related with the performance of conditioned responses, rather than with their acquisition.

A missense mutation in HERC1 provokes loss of cerebellar Purkinje cells, tremor, and unstable gait in tambaleante (tbl) mice. Recently, we have shown that before cerebellar degeneration takes place, the tbl mouse suffers from a reduction in the number of vesicles available for release at the neuromuscular junction (NMJ). The aim of the present work was to study to which extent the alteration in HERC1 may affect other cells in the nervous system and how this may influence the motor dysfunction observed in these mice. The functional analysis showed a consistent delay in the propagation of the action potential in mutant mice in comparison with control littermates. Morphological analyses of glial cells in motor axons revealed signs of compact myelin damage as tomacula and local hypermyelination foci. Moreover, we observed an alteration in non-myelinated terminal Schwann cells at the level of the NMJ. Additionally, we found a significant increment of phosphorylated Akt-2 in the sciatic nerve. Based on these findings, we propose a molecular model that could explain how mutated HERC1 in tbl mice affects the myelination process in the peripheral nervous system. Finally, since the myelin abnormalities found in tbl mice are histological hallmarks of neuropathic periphery diseases, tbl mutant mice could be considered as a new mouse model for this type of diseases.

Amyotrophic lateral sclerosis is a devastating motor neuron disease and to this day not curable. While 5–10% of patients inherit the disease (familiar ALS), up to 95% of patients are diagnosed with the sporadic form (sALS). ALS is characterized by the degeneration of upper motor neurons in the cerebral cortex and of lower motor neurons in the brainstem and spinal cord. The wobbler mouse resembles almost all phenotypical hallmarks of human sALS patients and is therefore an excellent motor neuron disease model. The motor neuron disease of the wobbler mouse develops over a time course of around 40 days and can be divided into three phases: p0, presymptomatic; p20, early clinical; and p40, stable clinical phase. Recent findings suggest an essential implication of the NAD+-producing enzyme Nmnat2 in neurodegeneration as well as maintenance of healthy axons. Here, we were able to show a significant downregulation of both gene and protein expression of Nmnat2 in the spinal cord of the wobbler mice at the stable clinical phase. The product of the enzyme NAD+ is also significantly reduced, and the values of the reactive oxygen species are significantly increased in the spinal cord of the wobbler mouse at p40. Thus, the deregulated expression of Nmnat2 appears to have a great influence on the cellular stress in the spinal cord of wobbler mice.

The motor deficit of the reeler mutants has largely been considered cerebellum related, and the developmental consequences of the cortex on reeler motor behavior have not been examined. We herein showed that there is a behavioral consequence to reeler mutation in models examined at cortex-dependent bimanual tasks that require forepaw dexterity. Using intracortical microstimulation, we found the forelimb representation in the motor cortex was significantly reduced in the reeler. The reeler cortex required a significantly higher current to evoke skeletal muscle movements, suggesting the cortical trans-synaptic propagation is disrupted. When the higher current was applied, the reeler motor representation was found preserved. To elucidate the influence of cerebellum atrophy and ataxia on the obtained results, the behavioral and neurophysiological findings in reeler mice were reproduced using the Disabled-1 (Dab1) cKO mice, in which the Reelin-Dab1 signal deficiency is confined to the cerebral cortex. The Dab1 cKO mice were further assessed at the single-pellet reach and retrieval task, displaying a lower number of successfully retrieved pellets. It suggests the abnormality confined to the cortex still reduced the dexterous motor performance. Although possible muscular dysfunction was reported in REELIN-deficient humans, the function of the reeler forelimb muscle examined by electromyography, morphology of neuromuscular junction and the expression level of choline acetyltransferase were normal. Our results suggest that the mammalian laminar structure is necessary for the forepaw skill performance and for trans-synaptic efficacy in the cortical output.

Absence seizures are known to originate from disruptions within the corticothalamocortical network; however, the precise underlying cellular and molecular mechanisms that induce hypersynchronicity and hyperexcitability are debated and likely to be complex and multifactorial. Recent studies implicate impaired thalamic GABAergic inhibition as a common feature in multiple animal models of absence epilepsy, including the well-established stargazer mouse model. Recently, we demonstrated region-specific increases in the whole tissue and synaptic levels of GABAA receptor (GABAAR) subunits α1 and β2, within the ventral posterior region of the thalamus in adult epileptic stargazer mice compared with nonepileptic control littermates. The objective of this study was to investigate whether such changes in GABAAR subunits α1 and β2 can be observed before the initiation of seizures, which occur around postnatal (PN) days 16-18 in stargazers. Semiquantitative western blotting was used to analyze the relative tissue level expression of GABAAR α1 and β2 subunits in the thalamus of juvenile stargazer mice compared with their nonepileptic control littermates at three different time points before the initiation of seizures. We show that there is a statistically significant increase in the expression of α1 and β2 subunits in the thalamus of stargazer mice, at the PN7-9 stage, compared with the control littermates, but not at PN10-12 and PN13-15 stages. These results suggest that an aberrant expression of GABAAR subunits α1 and β2 in the stargazers does not occur immediately before seizure onset and therefore is unlikely to directly contribute to the initiation of absence seizures.

Multiple sclerosis (MS) is considered a primary autoimmune disease; however, this view is increasingly being challenged in basic and clinical science arenas because of the growing body of clinical trials' data showing that exclusion of immune cells from the CNS only modestly slows disease progression to disability. Accordingly, there is significant need for expanding the scope of potential disease mechanisms to understand the etiology of MS. Concomitantly, the use of a broader range of pre-clinical animal models for characterizing existing efficacious clinical treatments may elucidate additional or unexpected mechanisms of action for these drugs that augment insight into MS etiology. Herein, we explore the in vivo mechanism of action of dimethyl fumarate, which has been shown to suppress oxidative stress and immune cell responses in psoriasis and MS. Rather than studying this compound in the context of an experimental autoimmune-induced attack on the CNS, we have used a genetic model of hypomyelination, male rumpshaker (rsh) mice, which exhibit oligodendrocyte metabolic stress and startle-induced subcortical myoclonus during development and into adulthood. We find that myoclonus is reduced 30-50% in treated mutants but we do not detect substantial changes in metabolic or oxidative stress response pathways, cytokine modulation, or myelin thickness (assessed by anova). All procedures involving vertebrate animals in this study were reviewed and approved by the IACUC committee at Wayne State University.

Immediately following ischemia, glutamate accumulates in the extracellular space and results in extensive stimulation of its receptors including N-methyl-D-aspartate (NMDA) and α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptors. A large amount of Ca2+ influx directly through the receptor-gated ion channels which leads to Ca2+ overload and triggers several downstream lethal reactions. As a result, cell dies via apoptosis or necrosis, or both. Death-associated protein kinase 1 (DAPK1) physically and functionally interacts with the NMDA receptor GluN2B subunit at extra-synaptic sites and this interaction acts as a central mediator for stroke damage. The goal of this study is to explore an effective strategy in the treatment of stroke with a molecular genetic manipulation to interrupt DAPK1-GluN2B interaction. We generated a mutant strain of mice with the conditional deletion of GluN2B C-terminal tail consisting of amino acids 886-1269 in the forebrain excitatory neurons (the GluN2B mutant mice) and tested the protective effects of this mutation in stroke damages. GluN2B mutation effectively disrupted the DAPK1-GluN2B interaction and inhibited extra-synaptic NMDA receptor currents without affecting synaptic NMDA receptor channel activity in the central neurons. GluN2B mutation protected against stroke damages both in vitro and in vivo and hence improved behavioral performance. Disruption of the DAPK1-GluN2B interaction is therapeutically effective against stroke damages.

Cognitive flexibility has traditionally been considered a frontal lobe function. However, converging evidence suggests involvement of a larger brain circuit which includes the cerebellum. Reciprocal pathways connecting the cerebellum to the prefrontal cortex provide a biological substrate through which the cerebellum may modulate higher cognitive functions, and it has been observed that cognitive inflexibility and cerebellar pathology co-occur in psychiatric disorders (e.g., autism, schizophrenia, addiction). However, the degree to which the cerebellum contributes to distinct forms of cognitive flexibility and rule learning is unknown. We tested lurcher↔wildtype aggregation chimeras which lose 0%–100% of cerebellar Purkinje cells during development on a touchscreen-mediated attentional set-shifting task to assess the contribution of the cerebellum to higher- and lower-order rule learning and cognitive flexibility. Purkinje cells, the sole output of the cerebellar cortex, ranged from 0 to 108, 390 in tested mice. Reversal learning and extradimensional set-shifting were impaired in mice with ≥ 95% Purkinje cell loss. Cognitive deficits were unrelated to motor deficits in ataxic mice. Acquisition of a simple visual discrimination and an attentional-set were unrelated to Purkinje cells. A positive relationship was observed between Purkinje cells and errors when exemplars from a novel, non-relevant dimension were introduced. Collectively, these data suggest that the cerebellum contributes to higher-order cognitive flexibility, lower-order cognitive flexibility, and attention to novel stimuli, but not the acquisition of higher- and lower-order rules. These data indicate that the cerebellar pathology observed in psychiatric disorders may underlie deficits involving cognitive flexibility and attention to novel stimuli.

Background/Aims: A novel ataxic mouse line was established from the offspring of a male mouse administered cyclophosphamide in a juvenile period. Methods: We have attempted to examine the phenotype and histopathological changes of affected mice. Furthermore, linkage analysis and sequencing of the mutant was performed to reveal the causative gene locus. Results and Conclusion: The affected mouse was characterized by heavy hind limb ataxia with gait disorder, which was first recognized at about 4 weeks of age and slowly progressed with advancing age. The phenotype was inherited in an autosomal recessive pattern. The genetic locus associated with the phenotype was named hak and mapped to 107,305,356-108,637,615 on chromosome 2qE3, non-coding sequences in the vicinity of Bdnf gene. Many spheroids were noticed in the cerebellar medulla and the brain stem. In the peripheral nerves, some sensory ganglionic cells showed deposition of NF-200 in the perikaryon and NF-200-positive spheroids in nerve fibers. No inflammatory cell infiltration was observed. In addition, the adult affected mouse had distinct iron deposition in the kidney and the liver, but not in the heart, the skeletal muscle and the central nervous system. These results suggest that the hak mouse has a tissue-specific impairment in the expression of a type of Bdnf transcripts.

Huntington’s disease (HD) is an inherited neurodegenerative disorder caused by a CAG repeat expansion within exon 1 of the huntingtin (HTT) gene. HTT mRNA contains 67 exons and does not always splice between exon 1 and exon 2 leading to the production of a small polyadenylated HTTexon1 transcript, and the full-length HTT mRNA has three 3′UTR isoforms. We have developed a QuantiGene multiplex panel for the simultaneous detection of all of these mouse Htt transcripts directly from tissue lysates and demonstrate that this can replace the more work-intensive Taqman qPCR assays. We have applied this to the analysis of brain regions from the zQ175 HD mouse model and wild type littermates at two months of age. We show that the incomplete splicing of Htt occurs throughout the brain and confirm that this originates from the mutant and not endogenous Htt allele. Given that HTTexon1 encodes the highly pathogenic exon 1 HTT protein, it is essential that the levels of all Htt transcripts can be monitored when evaluating HTT lowering approaches. Our QuantiGene panel will allow the rapid comparative assessment of all Htt transcripts in cell lysates and mouse tissues without the need to first extract RNA.