Clinical & Experimental Cardiology
Open Access

NET gene silencing by let-7i in postural tachycardia syndrome

22^nd World Cardiology Conference

December 11-12, 2017 | Rome, Italy

Abdul Waheed Khan, Mark Ziemann, Susan Corcoran, Harikrishnan K N, Jun Okabe, Haloom Rafehi, Scott S Maxwell, Murray D Esler and Assam El-Osta

The Alfred Medical Research and Education Precinct, Australia
The University of Melbourne, Australia
Monash University, Australia
The Chinese University of Hong Kong, Hong Kong

Posters & Accepted Abstracts: J Clin Exp Cardiolog

Abstract :

Introduction: While strongly implicated in postural tachycardia syndrome (POTS) and essential hypertension, considerable controversy exists regarding norepinephrine transporter (NET) loss-of-function. Increased heart rate in POTS is a malfunction of autonomic nervous system characterized by clinical symptoms of orthostatic intolerance, light-headedness, fatigue and near syncope on upright posture. NET is encoded by SLC6A2 (NET) gene. Current evidence suggests that NET is regulated by methyl CpG binding protein 2 (MeCP2). Here let-7i directed binding of MeCP2 at NET promoter was investigated. Furthermore, it was tested whether pharmacological histone deacetylase inhibition (HDACi) could restore NET expression. Methods: We developed a novel technique to identify RNAs bound to chromatin at NET prompter. Identification of chromatin associated RNAs at a specific locus can shed light on role of specific RNA in gene regulation affecting chromatin structure. Patients with POTS with the common clinical characteristics were recruited. Peripheral blood mononuclear cells (PBMCs) from POTS individuals were subjected to RNA immunoprecipitation sequencing (RIP-Seq), a novel RNA of isolated chromatin sequencing (RICh-Seq) and ex-vivo stimulation by pharmacological HDAC inhibitor suberoylanilide hydroxamic acid (SAHA (2�¼M)). Results: We show that let-7i is associated with NET suppression in POTS using unbiased RICh-Seq. Let-7i expression was higher in POTS as compared to healthy individuals. Increased let-7i binding at NET promoter and with MeCP2 in POTS subjects suggest that MeCP2 recruitment to chromatin is directed by let-7i. Ex vivo HDACi in PBMCs restored normal NET expression. Furthermore, let-7i inhibition in combination with HDACi alleviated transcriptional inhibition of NET. Conclusion: MeCP2 recruitment to SLC6A2 promoter is directed by let-7i. NET gene expression is restored by pharmacological HDAC inhibition suggesting this class of drugs may be useful therapeutics for POTS patients.