Immunomodulation is increasingly being recognised as a part of mental diseases. Here, we examined whether levels of immunological protein markers changed with depression, age, or the inhibitory neurotransmitter gamma-aminobutyric acid (GABA). An analysis of plasma samples from patients with a major depressive episode and control blood donors (CBD) revealed the expression of 67 inflammatory markers. Thirteen of these markers displayed augmented levels in patients compared to CBD. Twenty-one markers correlated with the age of the patients, whereas 10 markers correlated with the age of CBD. Interestingly, CST5 and CDCP1 showed the strongest correlation with age in the patients and CBD, respectively. IL-18 was the only marker that correlated with the MADRS-S scores of the patients. Neuronal growth factors (NGFs) were significantly enhanced in plasma from the patients, as was the average plasma GABA concentration. GABA modulated the release of seven cytokines in anti-CD3-stimulated peripheral blood mononuclear cells (PBMCs) from the patients. The study reveals significant changes in the plasma composition of small molecules during depression and identifies potential peripheral biomarkers of the disease.
The neural transmission and plasticity can be differentially modulated by various elements of the immune system. Interferon-gamma (IFN-gamma) is a "pro-inflammatory" cytokine mainly produced by T lymphocytes, activates its corresponding receptor and plays important roles under both homeostatic and inflammatory conditions. However, the impact of IFN-gamma on the gamma-aminobutyric acid (GABA)-mediated currents in the hippocampus, a major brain region involved in the cognitive function, has not been investigated. Here we detected abundant expression of both IFN-gamma receptor subunit gene transcripts (Ifngrl and Ifngr2) in the rat hippocampus by quantitative PCR. In addition, we pre-incubated rat hippocampal slices with IFN-gamma (100 ng/ml) and recorded GABA-activated spontaneous and miniature postsynaptic inhibitory currents (sIPSCs and mIPSCs) and tonic currents in hippocampal CAl pyramidal neurons by the whole-cell patch-clamp method. The pre-incubation with IFN-gamma increased the frequency but not the mean amplitude, rise time or decay time of both sIPSCs and mIPSCs in hippocampal CAl pyramidal neurons, suggesting a presynaptic effect of IFN-gamma. Moreover, the GABA-activated tonic currents were enhanced by IFN-gamma. In conclusion, the potentiation of GABAergic currents in hippocampal neurons by IFN-gamma may contribute to the disturbed neuronal excitability and cognitive dysfunction during neuroinflammation.
In pancreatic islets, the major cell-types are alpha, beta and delta cells. The gamma-aminobutyric acid (GABA) signalling system is expressed in human pancreatic islets. In single hormone transcript-expressing cells, we have previously characterized the functional properties of islet GABA(A) receptors (iGABA(A)Rs). Here, we extended these studies to islet cells expressing mRNAs for more than one hormone and sought for correlation between iGABA(A)R activity level and relative mRNA expression ratio. The single-cell RT-PCR in combination with the patch-clamp current recordings was used to examine functional properties of iGABA(A)Rs in the multiple hormone mRNA-expressing cells. We detected cells expressing double (alpha/beta, alpha/delta, beta/delta cell-types) and triple (alpha/beta/delta cell-type) hormone transcripts. The most common mixed-identity cell-type was the alpha/beta group where the cells could be grouped into beta- and alpha-like subgroups. The beta-like cells had low GCG/INS expression ratio (<0.6) and significantly higher frequency of iGABA(A)R single-channel openings than the alpha-like cells where the GCG/INS expression ratio was high (>1.2). The hormone expression levels and iGABA(A)R single-channel characteristics varied in the alpha/beta/delta cell-type. Clearly, multiple hormone transcripts can be expressed in islet cells whereas iGABA(A)R single-channel functional properties appear to be alpha or beta cell specific.
The etiology of hereditary ataxia syndromes is heterogeneous, and the mechanisms underlying these disorders are often unknown. Here, we utilized exome sequencing in two siblings with progressive ataxia and muscular weakness and identified a novel homozygous splice mutation (c.3020-1G > A) in neurofascin (NFASC). In RNA extracted from fibroblasts, we showed that the mutation resulted in inframe skipping of exon 26, with a deprived expression of the full-length transcript that corresponds to NFASC isoform NF186. To further investigate the disease mechanisms, we reprogrammed fibroblasts from one affected sibling to induced pluripotent stem cells, directed them to neuroepithelial stem cells and finally differentiated to neurons. In early neurogenesis, differentiating cells with selective depletion of the NF186 isoform showed significantly reduced neurite outgrowth as well as fewer emerging neurites. Furthermore, whole-cell patch-clamp recordings of patient-derived neuronal cells revealed a lower threshold for openings, indicating altered Na+ channel kinetics, suggesting a lower threshold for openings as compared to neuronal cells without the NFASC mutation. Taken together, our results suggest that loss of the full-length NFASC isoform NF186 causes perturbed neurogenesis and impaired neuronal biophysical properties resulting in a novel early-onset autosomal recessive ataxia syndrome.
We generated human iPS derived neural stem cells and differentiated cells from healthy control individuals and an individual with autism spectrum disorder carrying bi-allelic NRXN1-alpha deletion. We investigated the expression of NRXN1-alpha during neural induction and neural differentiation and observed a pivotal role for NRXN1-alpha during early neural induction and neuronal differentiation. Single cell RNA-seq pinpointed neural stem cells carrying NRXN1-alpha deletion shifting towards radial glia-like cell identity and revealed higher proportion of differentiated astroglia. Furthermore, neuronal cells carrying NRXN1-alpha deletion were identified as immature by single cell RNA-seq analysis, displayed significant depression in calcium signaling activity and presented impaired maturation action potential profile in neurons investigated with electrophysiology. Our observations propose NRXN1-alpha plays an important role for the efficient establishment of neural stem cells, in neuronal differentiation and in maturation of functional excitatory neuronal cells.
The previous reports on an addiction vulnerability marker in the human SLC4A7 gene encoding the Na/HCO3 transporter NBCn1 suggest that this pH-regulating protein may affect alcohol-related behavior and response. Here, we examined alcohol consumption and sensitivity to the sedative effects of alcohol in male NBCn1 knockout mice. These mice displayed lower pH in neurons than wildtype controls, determined by intracellular pH in hippocampal neuronal cultures. Neurons from knockout mice had a higher action potential threshold and a more depolarized membrane potential, thus reducing membrane excitability. In a two-bottle free choice procedure, knockout mice consumed more alcohol than controls and consistently increased alcohol consumption after repeated alcohol deprivation periods. Quinine and sucrose preference was similar between genotypes. Knockout mice showed increased propensity for alcohol-induced conditioned place preference. In loss of righting reflex assessment, knockout mice revealed increased sensitivity to alcohol-induced sedation and developed tolerance to the sedation after repeated alcohol administrations. Furthermore, chronic alcohol consumption caused NBCn1 downregulation in the hippocampus and striatum of mice and humans. These results demonstrate an important role of NBCn1 in regulation of alcohol consumption and sensitivity to alcohol-induced sedation.
Dravet syndrome (DS) is an early onset refractory epilepsy typically caused by de novo heterozygous variants in SCN1A encoding the a-subunit of the neuronal sodium channel Na(v)1.1. The syndrome is characterized by age related progression of seizures, cognitive decline and movement disorders. We hypothesized that the distinct neurodevelopmental features in DS are caused by the disruption of molecular pathways in Na(v)1.1 haploinsufficient cells resulting in perturbed neural differentiation and maturation. Here, we established DS-patient and control induced pluripotent stem cell derived neural progenitor cells (iPSC NPC) and GABAergic interneuronal (iPSC GABA) cells. The DS-patient iPSC GABA cells showed a shift in sodium current activation and a perturbed response to induced oxidative stress. Transcriptome analysis revealed specific dysregulations of genes for chromatin structure, mitotic progression, neural plasticity and excitability in DS-patient iPSC NPCs and DS-patient iPSC GABA cells versus controls. The transcription factors FOXM1 and E2F1, positive regulators of the disrupted pathways for histone modification and cell cycle regulation, were markedly up-regulated in DS-iPSC GABA lines. Our study highlights transcriptional changes and disrupted pathways of chromatin remodeling in Na(v)1.1 haploinsufficient GABAergic cells, providing a molecular framework that overlaps with that of neurodevelopmental disorders and other epilepsies.