Influence of NOS1AP Risk Variants on the Corrected QT (QTc) Interval in the Pharmacotherapy of Schizophrenia.

INTRODUCTION: The variants of the gene for nitric oxide synthase 1 adaptor protein (NOS1AP) are associated with schizophrenia and cardiovascular deficits involving corrected QT (QTc) interval prolongation. Here, we investigated a possible pharmacogenetic effect of antipsychotic treatment on QTc length in interaction with two NOS1AP variants (rs12143842 and rs10494366) whose minor alleles are associated with increased QTc interval length. METHODS: We conducted a retrospective analysis of electrocardiographic (ECG) and genotype data of 239 patients diagnosed with schizophrenia. We converted antipsychotics dosage to chlorpromazine equivalents and defined daily doses. We analysed the effects of the minor (i. e. rs12143842-CT/TT and rs10494366-GT/GG) and major (i. e. rs12143842-CC and rs10494366-TT) allele genotypes to QTc interval for female and male participants separately. RESULTS: As expected, rs12143842 and rs10494366 exhibit strong linkage disequilibrium. Both polymorphisms had no direct effect on antipsychotic use or QTc interval. However, there was a continuous increase in QTc interval with increasing antipsychotic dosage in males. For both variants, positive correlation of QTc length with antipsychotic dosage was found in homozygous male carriers of the major alleles (i. e. rs12143842-CC and rs10494366-TT), but not in minor allele carriers. There was no significant interaction between antipsychotic dosage and QTc interval for either genotype in female patients. CONCLUSIONS: In this study, a significant interaction was found between both NOS1AP variants, rs12143842 and rs10494366, and antipsychotic treatment on the QTc interval in a sex-dependent manner. Our findings might be relevant for adequate antipsychotic treatment in rs12143842 and rs10494366 major allele carriers.

Mouse Ataxin-2 Expansion Downregulates CamKII and Other Calcium Signaling Factors, Impairing Granule-Purkinje Neuron Synaptic Strength.

Spinocerebellar ataxia type 2 (SCA2) is caused by polyglutamine expansion in Ataxin-2 (ATXN2). This factor binds RNA/proteins to modify metabolism after stress, and to control calcium (Ca2+) homeostasis after stimuli. Cerebellar ataxias and corticospinal motor neuron degeneration are determined by gain/loss in ATXN2 function, so we aimed to identify key molecules in this atrophic process, as potential disease progression markers. Our Atxn2-CAG100-Knock-In mouse faithfully models features observed in patients at pre-onset, early and terminal stages. Here, its cerebellar global RNA profiling revealed downregulation of signaling cascades to precede motor deficits. Validation work at mRNA/protein level defined alterations that were independent of constant physiological ATXN2 functions, but specific for RNA/aggregation toxicity, and progressive across the short lifespan. The earliest changes were detected at three months among Ca2+ channels/transporters (Itpr1, Ryr3, Atp2a2, Atp2a3, Trpc3), IP3 metabolism (Plcg1, Inpp5a, Itpka), and Ca2+-Calmodulin dependent kinases (Camk2a, Camk4). CaMKIV-Sam68 control over alternative splicing of Nrxn1, an adhesion component of glutamatergic synapses between granule and Purkinje neurons, was found to be affected. Systematic screening of pre/post-synapse components, with dendrite morphology assessment, suggested early impairment of CamKIIα abundance together with the weakening of parallel fiber connectivity. These data reveal molecular changes due to ATXN2 pathology, primarily impacting excitability and communication.

Establishing an effective dose for chronic intracerebroventricular administration of clozapine in mice.

OBJECTIVE: Despite its numerous side effects, clozapine is still the most effective antipsychotics making it an ideal reference substance to validate the efficacy of novel compounds for the treatment of schizophrenia. However, blood-brain barrier permeability for most new molecular entities is unknown, requiring central delivery. Thus, we performed a dose-finding study for chronic intracerebroventricular (icv) delivery of clozapine in mice. METHODS: Specifically, we implanted wild-type C57BL/6J mice with osmotic minipumps (Alzet) delivering clozapine at a rate of 0.15 µl/h at different concentrations (0, 3.5, 7 and 14 mg/ml, i.e. 0, 12.5, 25 and 50 µg/day). Mice were tested weekly in a modified SHIRPA paradigm, for locomotor activity in the open field and for prepulse inhibition (PPI) of the acoustic startle response (ASR) for a period of 3 weeks. RESULTS: None of the clozapine concentrations caused neurological deficits or evident gross behavioural alterations in the SHIRPA paradigm. In male mice, clozapine had no significant effect on locomotor activity or PPI of the ASR. In female mice, the 7 and 14 mg/ml dose of clozapine significantly affected both open field activity and PPI, while 3.5 mg/ml of clozapine increased PPI but had no effects on locomotor activity. CONCLUSION: Our findings indicate that 7 mg/ml may be the optimal dose for chronic icv delivery of clozapine in mice, allowing comparison to screen for novel antipsychotic compounds.

Hippocampal overexpression of NOS1AP promotes endophenotypes related to mental disorders.

BACKGROUND: Nitric oxide synthase 1 adaptor protein (NOS1AP; previously named CAPON) is linked to the glutamatergic postsynaptic density through interaction with neuronal nitric oxide synthase (nNOS). NOS1AP and its interaction with nNOS have been associated with several mental disorders. Despite the high levels of NOS1AP expression in the hippocampus and the relevance of this brain region in glutamatergic signalling as well as mental disorders, a potential role of hippocampal NOS1AP in the pathophysiology of these disorders has not been investigated yet. METHODS: To uncover the function of NOS1AP in hippocampus, we made use of recombinant adeno-associated viruses to overexpress murine full-length NOS1AP or the NOS1AP carboxyterminus in the hippocampus of mice. We investigated these mice for changes in gene expression, neuronal morphology, and relevant behavioural phenotypes. FINDINGS: We found that hippocampal overexpression of NOS1AP markedly increased the interaction of nNOS with PSD-95, reduced dendritic spine density, and changed dendritic spine morphology at CA1 synapses. At the behavioural level, we observed an impairment in social memory and decreased spatial working memory capacity. INTERPRETATION: Our data provide a mechanistic explanation for a highly selective and specific contribution of hippocampal NOS1AP and its interaction with the glutamatergic postsynaptic density to cross-disorder pathophysiology. Our findings allude to therapeutic relevance due to the druggability of this molecule. FUNDING: This study was funded in part by the DFG, the BMBF, the Academy of Finland, the NIH, the Japanese Society of Clinical Neuropsychopharmacology, the Ministry of Education of the Russian Federation, and the European Community.