Maria Petkova , PhD 1 , Andrew J. Atkinson , PhD 1 , Joseph Yanni , PhD 1 , Luke Stuart , MRes 1 , Abimbola J. Aminu , MRes 1 , Alexandra D. Ivanova , MSc 6 , Ksenia B. Pustovit , PhD 6 , Connor Geragthy , MBChB 1 , Amy Feather , MRes 1 , Ning Li , PhD 2 , Yu Zhang , PhD 1 , Delvac Oceandy , PhD 1 , Filip Perde , PhD 3 , Peter Molenaar , PhD 4 , 5 , Alicia D’Souza , PhD 1 , Vadim V. Fedorov , PhD 2 , Halina Dobrzynski , PhD , 1 , 7
16 October 2020
The sinus node (SN) is the primary pacemaker of the heart. SN myocytes possess distinctive action potential morphology with spontaneous diastolic depolarization because of a unique expression of ion channels and Ca 2+‐handling proteins. MicroRNAs (miRs) inhibit gene expression. The role of miRs in controlling the expression of genes responsible for human SN pacemaking and conduction has not been explored. The aim of this study was to determine miR expression profile of the human SN as compared with that of non‐pacemaker atrial muscle.
SN and atrial muscle biopsies were obtained from donor or post‐mortem hearts (n=10), histology/immunolabeling were used to characterize the tissues, TaqMan Human MicroRNA Arrays were used to measure 754 miRs, Ingenuity Pathway Analysis was used to identify miRs controlling SN pacemaker gene expression. Eighteen miRs were significantly more and 48 significantly less abundant in the SN than atrial muscle. The most interesting miR was miR‐486‐3p predicted to inhibit expression of pacemaking channels: HCN1 (hyperpolarization‐activated cyclic nucleotide‐gated 1), HCN4, voltage‐gated calcium channel (Ca v)1.3, and Ca v3.1. A luciferase reporter gene assay confirmed that miR‐486‐3p can control HCN4 expression via its 3′ untranslated region. In ex vivo SN preparations, transfection with miR‐486‐3p reduced the beating rate by ≈35±5% ( P<0.05) and HCN4 expression ( P<0.05).