Altered neuroepithelial morphogenesis and migration defects in iPSC-derived cerebral organoids and 2D neural stem cells in familial bipolar disorder.

Bipolar disorder (BD) is a severe mental illness that can result from neurodevelopmental aberrations, particularly in familial BD, which may include causative genetic variants. In the present study, we derived cortical organoids from BD patients and healthy (control) individuals from a clinically dense family in the Indian population. Our data reveal that the patient organoids show neurodevelopmental anomalies, including organisational, proliferation and migration defects. The BD organoids show a reduction in both the number of neuroepithelial buds/cortical rosettes and the ventricular zone size. Additionally, patient organoids show a lower number of SOX2-positive and EdU-positive cycling progenitors, suggesting a progenitor proliferation defect. Further, the patient neurons show abnormal positioning in the ventricular/intermediate zone of the neuroepithelial bud. Transcriptomic analysis of control and patient organoids supports our cellular topology data and reveals dysregulation of genes crucial for progenitor proliferation and neuronal migration. Lastly, time-lapse imaging of neural stem cells in 2D in vitro cultures reveals abnormal cellular migration in BD samples. Overall, our study pinpoints a cellular and molecular deficit in BD patient-derived organoids and neural stem cell cultures.

Two photon imaging of calcium responses in murine Purkinje neurons.

Purkinje neurons (PNs) are an important component of the motor learning and coordination circuit and are affected in spino-cerebellar ataxias. Maintaining healthy PNs in cerebellar slices and recording their Ca2+ transients can be challenging. Here, we describe a protocol for measuring Ca2+ transients in PNs from adult mice, including problem-solving tips. This protocol can be used to measure neuronal excitability and agonist-mediated Ca2+ signaling in cerebellar slices expressing a genetic Ca2+ reporter in all PNs, thus improving yield of data. For complete details on the use and execution of this profile, please refer to Dhanya and Hasan (2021).

Purkinje Neurons with Loss of STIM1 Exhibit Age-Dependent Changes in Gene Expression and Synaptic Components.

The stromal interaction molecule 1 (STIM1) is an ER-Ca2+ sensor and an essential component of ER-Ca2+ store operated Ca2+ entry. Loss of STIM1 affects metabotropic glutamate receptor 1 (mGluR1)-mediated synaptic transmission, neuronal Ca2+ homeostasis, and intrinsic plasticity in Purkinje neurons (PNs). Long-term changes of intracellular Ca2+ signaling in PNs led to neurodegenerative conditions, as evident in individuals with mutations of the ER-Ca2+ channel, the inositol 1,4,5-triphosphate receptor. Here, we asked whether changes in such intrinsic neuronal properties, because of loss of STIM1, have an age-dependent impact on PNs. Consequently, we analyzed mRNA expression profiles and cerebellar morphology in PN-specific STIM1 KO mice (STIM1PKO ) of both sexes across ages. Our study identified a requirement for STIM1-mediated Ca2+ signaling in maintaining the expression of genes belonging to key biological networks of synaptic function and neurite development among others. Gene expression changes correlated with altered patterns of dendritic morphology and greater innervation of PN dendrites by climbing fibers, in aging STIM1PKO mice. Together, our data identify STIM1 as an important regulator of Ca2+ homeostasis and neuronal excitability in turn required for maintaining the optimal transcriptional profile of PNs with age. Our findings are significant in the context of understanding how dysregulated calcium signals impact cellular mechanisms in multiple neurodegenerative disorders.SIGNIFICANCE STATEMENT In Purkinje neurons (PNs), the stromal interaction molecule 1 (STIM1) is required for mGluR1-dependent synaptic transmission, refilling of ER Ca2+ stores, regulation of spike frequency, and cerebellar memory consolidation. Here, we provide evidence for a novel role of STIM1 in maintaining the gene expression profile and optimal synaptic connectivity of PNs. Expression of genes related to neurite development and synaptic organization networks is altered in PNs with persistent loss of STIM1. In agreement with these findings the dendritic morphology of PNs and climbing fiber innervations on PNs also undergo significant changes with age. These findings identify a new role for dysregulated intracellular calcium signaling in neurodegenerative disorders and provide novel therapeutic insights.

Deficits Associated With Loss of STIM1 in Purkinje Neurons Including Motor Coordination Can Be Rescued by Loss of Septin 7.

Septins are cytoskeletal proteins that can assemble to form heteromeric filamentous complexes and regulate a range of membrane-associated cellular functions. SEPT7, a member of the septin family, functions as a negative regulator of the plasma membrane-localized store-operated Ca2+ entry (SOCE) channel, Orai in Drosophila neurons, and in human neural progenitor cells. Knockdown of STIM, a Ca2+ sensor in the endoplasmic reticulum (ER) and an integral component of SOCE, leads to flight deficits in Drosophila that can be rescued by partial loss of SEPT7 in neurons. Here, we tested the effect of reducing and removing SEPT7 in mouse Purkinje neurons (PNs) with the loss of STIM1. Mice with the complete knockout of STIM1 in PNs exhibit several age-dependent changes. These include altered gene expression in PNs, which correlates with increased synapses between climbing fiber (CF) axons and Purkinje neuron (PN) dendrites and a reduced ability to learn a motor coordination task. Removal of either one or two copies of the SEPT7 gene in STIM1 KO PNs restored the expression of a subset of genes, including several in the category of neuron projection development. Importantly, the rescue of gene expression in these animals is accompanied by normal CF-PN innervation and an improved ability to learn a motor coordination task in aging mice. Thus, the loss of SEPT7 in PNs further modulates cerebellar circuit function in STIM1 KO animals. Our findings are relevant in the context of identifying SEPT7 as a putative therapeutic target for various neurodegenerative diseases caused by reduced intracellular Ca2+ signaling.

Single nucleotide polymorphisms of ADRB2 gene and their association with susceptibility for Plasmodium falciparum malaria and asthma in an Indian population.

The essential route to blood parasitaemia in malaria, erythrocyte invasion is facilitated by activation of the G-protein coupled receptor signaling pathway mediated by the ß2-adrenoreceptor as one of the proteins on the surface of red blood cells. The effectiveness of bronchodilators and inhaled corticosteroids in the clinical treatment for asthma patients also depend on polymorphisms in the ß2-adrenoreceptor gene (ADRB2). In a case control study, individuals affected by Plasmodium falciparum malaria, asthma and controls were tested for association of six ADRB2 single nucleotide polymorphisms (SNPs) viz. rs1042711, rs1801704, rs1042713, rs1042714, rs1042717 and rs1042718, by direct DNA sequencing. The rs1801704 locus was significantly associated with malaria when compared against controls. The rs1042713 polymorphism was associated with forced expiratory flow between 25% and 75% of the FVC in asthma patients, pre (p=0.048) and post (p=0.038) treatment measurements. Predicted haplotype of the six SNPs computed from genotype data showed T-T-A-C-G-C conferred significant risk of malaria (p=0.02) whereas T-T-A-C-G-A was associated with risk of asthma (p=0.02). The haplotype T-T-G-C-G-C was protective against both malaria (p=0.02) as well as asthma (p=0.026) and C-C-G-G-G-C was protective uniquely for asthma (p=0.04). A significant outcome was that all variant alleles at the SNP loci were part of the haplotype conferring resistance to malaria disease and asthma, except rs1042713 and rs1042718 which showed very high frequency in asthma. The pairwise linkage disequilibrium (LD) estimates showed a distinct LD block of all SNP loci (D'=1 or >0.8) in malaria patients. This characteristic haplotype block was disrupted in the controls due to non-significant pairwise LD of the SNP loci; and a more extensive disruption of the block was noted in asthma patients. The study provides evidence for the proposed role of ß2-adrenoreceptor mediated molecular mechanisms in etiology of malaria, as well as asthma disease and drug response, for further clinical and therapeutic application studies.