single-cell-electroporation-across-different-organotypic-slice

Single-Cell Electroporation across Different Organotypic Slice Culture of Mouse Hippocampal Excitatory and Class-Specific Inhibitory Neurons

Electroporation has established itself as a critical method for transferring specific genes into cells to understand their function. Here, we describe a ...

University of Massachusetts Medical School

Alzheimer's disease (AD) is characterized by the progressive destruction and dysfunction of central neurons. AD patients commonly have unprovoked seizures compared with age-matched controls. Amyloid peptide-related inflammation is thought to be an important aspect of AD pathogenesis. We previously reported that NLRP3 inflammasome KO mice, when bred into APPswe/PS1ΔE9 (APP/PS1) mice, are completely protected from amyloid-induced AD-like disease, presumably because they cannot produce mature IL1β or IL18. To test the role of IL18, we bred IL18KO mice with APP/PS1 mice. Surprisingly, IL18KO/APP/PS1 mice developed a lethal seizure disorder that was completely reversed by the anticonvulsant levetiracetam. IL18-deficient AD mice showed a lower threshold in chemically induced seizures and a selective increase in gene expression related to increased neuronal activity. IL18-deficient AD mice exhibited increased excitatory synaptic proteins, spine density, and basal excitatory synaptic transmission that contributed to seizure activity. This study identifies a role for IL18 in suppressing aberrant neuronal transmission in AD.

Inflammasome-derived cytokine IL18 suppresses amyloid-induced seizures in Alzheimer-prone mice.

The dorsal raphe nucleus (DR) is a crucial source of serotonin (5-HT) neurons involved in the regulation of stress-induced depression. Estrogen receptors have been identified in the DR, yet the role of estrogen in modulating this adaptive response is incompletely understood. The current study investigated the effects of different dosages of estradiol (E2, 10 and 50 μg/rat/day for 11 consecutive days) and selective estrogen receptor modulators: Diarylpropionitrile (DPN, 10 μg/rat/day for 11 consecutive days) and propyl pyrazole triol (PPT, 10 μg/rat/day for 11 consecutive days) on behavior and the expression of tryptophan hydroxylase (TPH) and glucocorticoid receptor in the DR of ovariectomized rats subjected to the forced swim test (FST). 10 μg E2 and DPN, an estrogen receptor β agonist, increased swimming and decreased immobility in the FST, while 50 μg E2 and PPT, an estrogen receptor α agonist, failed to influence the behavior of the rats in the FST. Similarly, 10 μg E2 and DPN increased TPH protein expression in the DR, while 50 μg E2 and PPT did not. Both 10 μg E2 and 50 μg E2 increased glucocorticoid receptor protein expression in the DR. Interestingly, 50 μg E2 led to a greater increase in plasma corticosterone levels compared with 10 μg E2. These observations suggest that a physiological dosage of E2 reduces depressive behavior and enhances TPH expression. High dosage of E2 lacks antidepressant activity in part due to heightened effects on corticosterone levels, which may conversely decrease TPH expression in the DR.

Physiological dosages of estradiol and diarylpropionitrile decrease depressive behavior and increase tryptophan hydroxylase expression in the dorsal raphe nucleus of rats subjected to the forced swim test.

Synapses, highly specialized membrane junctions between neurons, connect presynaptic neurotransmitter release sites and postsynaptic ligand-gated channels. Neurexins (Nrxns), a family of presynaptic adhesion molecules, have been characterized as major regulators of synapse development and function. Via their extracellular domains, Nrxns bind to different postsynaptic proteins, generating highly diverse functional readouts through their postsynaptic binding partners. Not surprisingly given these versatile protein interactions, mutations and deletions of Nrxn genes have been identified in patients with autism spectrum disorders, intellectual disabilities, and schizophrenia. Therefore, elucidating the expression profiles of Nrxns in the brain is of high significance. Here, using chromogenic and fluorescent in situ hybridization, we characterize the expression patterns of Nrxn isoforms throughout the brain. We found that each Nrxn isoform displays a unique expression profile in a region-, cell type-, and sensory system-specific manner. Interestingly, we also found that αNrxn1 and αNrxn2 mRNAs are expressed in non-neuronal cells, including astrocytes and oligodendrocytes. Lastly, we found diverse expression patterns of genes that encode Nrxn binding proteins, such as Neuroligins (Nlgns), Leucine-rich repeat transmembrane neuronal protein (Lrrtms) and Latrophilins (Adgrls), suggesting that Nrxn proteins can mediate numerous combinations of trans-synaptic interactions. Together, our anatomical profiling of Nrxn gene expression reflects the diverse roles of Nrxn molecules.

Differential expression of neurexin genes in the mouse brain.

Treatment and services for psychosis: Are college campuses a novel frontier for early detection and intervention?

Exogenous gene introduction by transfection is one of the most important approaches for understanding the function of specific genes at the cellular level. Electroporation has a long-standing history as a versatile gene delivery technique in vitro and in vivo. However, it has been underutilized in vitro because of technical difficulty and insufficient transfection efficiency.

A highly efficient method for single-cell electroporation in mouse organotypic hippocampal slice culture.

Synapse formation is a dynamic process essential for the development and maturation of the neuronal circuitry in the brain. At the synaptic cleft, trans-synaptic protein-protein interactions are major biological determinants of proper synapse efficacy. The balance of excitatory and inhibitory synaptic transmission (E-I balance) stabilizes synaptic activity, and dysregulation of the E-I balance has been implicated in neurodevelopmental disorders, including autism spectrum disorders. However, the molecular mechanisms underlying the E-I balance remain to be elucidated. Here, using single-cell transcriptomics, immunohistochemistry, and electrophysiology approaches to murine CA1 pyramidal neurons obtained from organotypic hippocampal slice cultures, we investigate neuroligin () genes that encode a family of postsynaptic adhesion molecules known to shape excitatory and inhibitory synaptic function. We demonstrate that the NLGN3 protein differentially regulates inhibitory synaptic transmission in a splice isoform-dependent manner at hippocampal CA1 synapses. We also found that distinct subcellular localizations of the NLGN3 isoforms contribute to the functional differences observed among these isoforms. Finally, results from single-cell RNA-Seq analyses revealed that  and  are the major murine  genes and that the expression levels of the  splice isoforms are highly diverse in CA1 pyramidal neurons. Our results delineate isoform-specific effects of  genes on the E-I balance in the murine hippocampus.

Article	Year
Inflammasome-derived cytokine IL18 suppresses amyloid-induced seizures in Alzheimer-prone mice. Proceedings of the National Academy of Sciences of the United States of America\| PubMed ID: 30127003	2018
Physiological dosages of estradiol and diarylpropionitrile decrease depressive behavior and increase tryptophan hydroxylase expression in the dorsal raphe nucleus of rats subjected to the fo... Neuroreport\| PubMed ID: 30379725	2019
Differential expression of neurexin genes in the mouse brain. The Journal of comparative neurology\| PubMed ID: 30761534	2019
Treatment and services for psychosis: Are college campuses a novel frontier for early detection and intervention? Psychiatry research\| PubMed ID: 31813595	2020
A highly efficient method for single-cell electroporation in mouse organotypic hippocampal slice culture. Journal of neuroscience methods\| PubMed ID: 32126275	2020
Neuroligin3 splice isoforms shape inhibitory synaptic function in the mouse hippocampus. The Journal of biological chemistry\| PubMed ID: 32381505	2020

Amy Cheung

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