miR-206 Represses Hypertrophy of Myogenic Cells but Not Muscle Fibers via Inhibition of HDAC4

Abstract

microRNAs regulate the development of myogenic progenitors, and the formation of skeletal muscle fibers. However, the role miRNAs play in controlling the growth and adaptation of post-mitotic musculature is less clear. Here, we show that inhibition of the established pro-myogenic regulator miR-206 can promote hypertrophy and increased protein synthesis in post-mitotic cells of the myogenic lineage. We have previously demonstrated that histone deacetylase 4 (HDAC4) is a target of miR-206 in the regulation of myogenic differentiation. We confirmed that inhibition of miR-206 de-repressed HDAC4 accumulation in cultured myotubes. Importantly, inhibition of HDAC4 activity by valproic acid or sodium butyrate prevented hypertrophy of myogenic cells otherwise induced by inhibition of miR-206. To test the significance of miRNA-206 as a regulator of skeletal muscle mass in vivo, we designed recombinant adeno-associated viral vectors (rAAV6 vectors) expressing miR-206, or a miR-206 “sponge,” featuring repeats of a validated miR-206 target sequence. We observed that over-expression or inhibition of miR-206 in the muscles of mice decreased or increased endogenous HDAC4 levels respectively, but did not alter muscle mass or myofiber size. We subsequently manipulated miR-206 levels in muscles undergoing follistatin-induced hypertrophy or denervation-induced atrophy (models of muscle adaptation where endogenous miR-206 expression is altered). Vector-mediated manipulation of miR-206 activity in these models of cell growth and wasting did not alter gain or loss of muscle mass respectively. Our data demonstrate that although the miR-206/HDAC4 axis operates in skeletal muscle, the post-natal expression of miR-206 is not a key regulator of basal skeletal muscle mass or specific modes of muscle growth and wasting. These studies support a context-dependent role of miR-206 in regulating hypertrophy that may be dispensable for maintaining or modifying the adult skeletal muscle phenotype – an important consideration in relation to the development of therapeutics designed to manipulate microRNA activity in musculature.

Discovery of Potential Therapeutic miRNA Targets in Cardiac Ischemia–Reperfusion Injury

“…It is believed to be a muscle enriched miRNA and might play a role in cardiac hypertrophy. 40 Overexpression may reduce the effects of inflammatory cytokines. 41 These results point to plausible cardioprotective mechanisms for these miRNAs.…”

miR-378a-3p promotes differentiation and inhibits proliferation of myoblasts by targeting HDAC4 in skeletal muscle development

“…These miRNAs also play roles in muscle development in mammals. Previous studies reported that several miRNAs, such as miR-1, 47 miR-133, 31,45,49 and miR-206, 3,19,42 are musclespecific miRNAs because they are key regulators in muscle development in human, pigs, and rats. Others miRNAs may also contribute to muscle development.…”

Heme Oxygenase-1 Controls an HDAC4-miR-206 Pathway of Oxidative Stress in Rhabdomyosarcoma

“…In the reduced state, HDAC domain associates with the nuclear export signal (NES) and blocks its exposure to CRM1 exportin. After oxidation of Cys-667 and Cys-669, the HDAC domain dissociates from the NES, which is exposed to CRM1, inducing the nuclear export (46). Such mechanism has been described in lung carcinoma, where upon oxidation, HDAC4 was expulsed from the nucleus, leading to derepression of miR-206 (28).…”

“…HDAC4 is also a bona fide target of miR-206 (43) with miR-206 inhibiting expression of HDAC4 and augmenting histone acetylation (46). Moreover, miR-206 is not only a repressor of HDAC4 but also its downstream target.…”