Increased hippocampal excitability in miR-324-null mice

Dan J Hayman,Ian M Clark,Colin G Miles,Matt J Barter,Fiona E N Lebeau,Katarzyna A Piróg,Michael D Briggs,Robert M Jackson,Dimitra Tsompani,Tamara Modebadze,Gavin J Clowry,Yao Hao,Hua Lin,Kat Cheung,Jamie Soul,David A Young,Sarah Charlton

doi:10.1038/s41598-021-89874-1

Abstract

MicroRNAs are non-coding RNAs that act to downregulate the expression of target genes by translational repression and degradation of messenger RNA molecules. Individual microRNAs have the ability to specifically target a wide array of gene transcripts, therefore allowing each microRNA to play key roles in multiple biological pathways. miR-324 is a microRNA predicted to target thousands of RNA transcripts and is expressed far more highly in the brain than in any other tissue, suggesting that it may play a role in one or multiple neurological pathways. Here we present data from the first global miR-324-null mice, in which increased excitability and interictal discharges were identified in vitro in the hippocampus. RNA sequencing was used to identify differentially expressed genes in miR-324-null mice which may contribute to this increased hippocampal excitability, and 3′UTR luciferase assays and western blotting revealed that two of these, Suox and Cd300lf, are novel direct targets of miR-324. Characterisation of microRNAs that produce an effect on neurological activity, such as miR-324, and identification of the pathways they regulate will allow a better understanding of the processes involved in normal neurological function and in turn may present novel pharmaceutical targets in treating neurological disease.

Highlights

MicroRNAs are non-coding RNAs that act to downregulate the expression of target genes by translational repression and degradation of messenger RNA molecules
Amongst the targets relevant for neurological activity, App, the gene encoding the amyloid precursor p rotein[32], is one of the most confidently p redicted[4,33], potentially linking miR-324-5p to Alzheimer’s D isease34. miR-324-5p has been investigated in relation to epilepsy; in a murine model of epilepsy, whereby wild-type (WT) mice were injected with pilocarpine in order to evoke seizure activity, the use of a miR-324-5p antagomir was found to reduce the incidence of epileptic e vents[30], purportedly by downregulating the expression of Kcnd[2], a gene encoding the potassium channel protein Kv4.229,30
In order to determine whether global miR-324-null mice exhibited any deficits in the generation of network activity, the local field potential (LFP) was recorded from the CA3 stratum radiatum in hippocampal slices obtained from 19 to 21 week old female miR-324-null and WT mice (16 slices obtained from 6 mice, for each genotype)

Summary

Introduction

MicroRNAs are non-coding RNAs that act to downregulate the expression of target genes by translational repression and degradation of messenger RNA molecules. MiR-324 is a microRNA predicted to target thousands of RNA transcripts and is expressed far more highly in the brain than in any other tissue, suggesting that it may play a role in one or multiple neurological pathways. Dicer[1] encodes an essential endoribonuclease for miRNA processing and conditional Dicer[1] knockout models (KO) in individual neuronal populations present with severe neurological abnormalities[18,19,20,21]. These are most commonly due to upregulation of apoptotic pathways or downregulation of cell proliferation, resulting in reduced brain size. A detailed investigation into the cause of the association between miR-324 and epilepsy has not yet been reported

Methods

Results

Conclusion