Demonstration of the presence of the “deleted” miR-122 gene in HepG2 cells

Abstract

Aim: MicroRNAs (miRs) are involved in regulation of gene expression and may play a role in development of hypertension.Methods: Three months old C57BL/6J mice were treated angiotensin II (AngII, 490ng/kg/min) or control buffer using miniosmotic pumps for 2 weeks. Isolated RNA from aorta and perivascular adipose tissue (PVAT) was reverse transcribed using Megaplex primer pools and profiled with TaqMAn Rodent microRNA Array. Statistical tests were performed on normalized CT values in R (HTqPCR package) or DataAssist. Results: From 381 studied miRs 103 was differentially expressed in aortas and 134 in PVAT (Ct<32). Both principal components and hierarchical clustering analyses using all expressed miRs in aorta and PVAT separated hypertensive from control animals. In aortas, there were 29 and 24 differentially expressed miRs, at FDR adjusted p<0.05, between treatment groups, while using global mean or quantile normalization method respectively with 19 microRNAs overlapping. Out of these 7 miRs were overexpressed in aortas of hypertensive mice as compared to controls. Only mir-21 and mir-142-3p were significantly expressed after Bonferroni correction (3.5-fold induction) in hypertensive animals. Similar analysis identified 16 differently expressed miRs in PVAT between groups. Mir-214 was the only miR significantly overexpressed (8-fold induction) in hypertensive animals after Bonferroni correction. Effects of mir-21 and mir-214 on vascular function will be addressed in respective knockout models. Conclusions: AngII infusion changes miR profiles in murine aortas and PVAT. Mir-21 is the most upregulated in aortas whereas mir-214 is the most upregulated miR in PVAT, which can affect development of vascular dysfunction.

miRs*: Innocent bystanders only?

“…Like miR‐122, miR‐122* is decreased in hepatocellular carcinoma compared to nontumoral liver, suggesting that the inhibition of transcription very likely takes place at the primary miR level. Why this happens has not been investigated in this context yet, but the work of Hamad and colleagues suggests that epigenetic silencing (identified in HepG2 cells) could be a possible mechanism . In other cases, where the ratio between the two strands is changed, different mechanisms have been proposed.…”

“…Why this happens has not been investigated in this context yet, but the work of Hamad and colleagues suggests that epigenetic silencing (identified in HepG2 cells) could be a possible mechanism. (5) In other cases, where the ratio between the two strands is changed, different mechanisms have been proposed. For example, Winter and Diederichs showed that in the case of Let-7a the guide-to-passenger strand ratio can be actively regulated by Human Argonaute 3, which specifically enhances the passenger strand expression.…”