MicroRNA-486–dependent modulation of DOCK3/PTEN/AKT signaling pathways improves muscular dystrophy–associated symptoms
Matthew S. Alexander, … , Jeffrey J. Widrick, Louis M. Kunkel
Matthew S. Alexander, … , Jeffrey J. Widrick, Louis M. Kunkel
Published May 1, 2014
Citation Information: J Clin Invest. 2014;124(6):2651-2667. https://doi.org/10.1172/JCI73579.
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Research Article Muscle biology

MicroRNA-486–dependent modulation of DOCK3/PTEN/AKT signaling pathways improves muscular dystrophy–associated symptoms

Abstract

Duchenne muscular dystrophy (DMD) is caused by mutations in the gene encoding dystrophin, which results in dysfunctional signaling pathways within muscle. Previously, we identified microRNA-486 (miR-486) as a muscle-enriched microRNA that is markedly reduced in the muscles of dystrophin-deficient mice (Dmdmdx-5Cv mice) and in DMD patient muscles. Here, we determined that muscle-specific transgenic overexpression of miR-486 in muscle of Dmdmdx-5Cv mice results in reduced serum creatine kinase levels, improved sarcolemmal integrity, fewer centralized myonuclei, increased myofiber size, and improved muscle physiology and performance. Additionally, we identified dedicator of cytokinesis 3 (DOCK3) as a miR-486 target in skeletal muscle and determined that DOCK3 expression is induced in dystrophic muscles. DOCK3 overexpression in human myotubes modulated PTEN/AKT signaling, which regulates muscle hypertrophy and growth, and induced apoptosis. Furthermore, several components of the PTEN/AKT pathway were markedly modulated by miR-486 in dystrophin-deficient muscle. Skeletal muscle–specific miR-486 overexpression in Dmdmdx-5Cv animals decreased levels of DOCK3, reduced PTEN expression, and subsequently increased levels of phosphorylated AKT, which resulted in an overall beneficial effect. Together, these studies demonstrate that stable overexpression of miR-486 ameliorates the disease progression of dystrophin-deficient skeletal muscle.

Authors

Matthew S. Alexander, Juan Carlos Casar, Norio Motohashi, Natássia M. Vieira, Iris Eisenberg, Jamie L. Marshall, Molly J. Gasperini, Angela Lek, Jennifer A. Myers, Elicia A. Estrella, Peter B. Kang, Frederic Shapiro, Fedik Rahimov, Genri Kawahara, Jeffrey J. Widrick, Louis M. Kunkel

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Figure 8

DOCK3 overexpression induces apoptosis and affects PTEN/AKT and RAC1/RHOA signaling in primary human myotubes.

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DOCK3 overexpression induces apoptosis and affects PTEN/AKT and RAC1/RHO...
(A) Phase microscopy images of primary human myotubes expressing either a control vector (pCI-Neo) or HA-DOCK3. Stable-transfected (vector or HA-DOCK3) primary myoblasts were differentiated into myotubes by adding differentiation medium for 72 hours prior to imaging. Note the large phase-bright cell aggregates in the DOCK3-overexpressing primary myotubes as compared with vector controls. Scale bars: 100 μm. (B) Activated caspase-3 is induced in primary human myotubes that overexpress DOCK3. Three replicates in separate wells were used for both DOCK3 and vector controls. (C) Western blot images showing DOCK3 overexpression affects PTEN/AKT signaling levels. Western blot images of HA (DOCK3), PTEN, pAKT (S473 and T308), AKT (pan/recognizes all 3 AKT isoforms), PROCASPASE3 (top arrowhead), cleaved CASPASE-3 (bottom arrowhead), and a GAPDH loading control taken from 30 μg of protein whole-cell lysates overexpressing either the control empty vector or HA-DOCK3 in primary human myotubes. (D) TUNEL assay on DOCK3-overexpressing and control vector–overexpressing primary human myotubes. The TUNEL-positive nuclei (red) are costained with DAPI (blue) in the vector (pCI-HA) control– and HA-DOCK3–overexpressing samples. (E) The percentage of TUNEL-positive myonuclei in the vector control– or HA-DOCK3–overexpressing normal primary myotubes is shown on the graph. Two-hundred myonuclei were counted from at least 10 different fields for each condition. Three separate 2-well chamber slides were used in this experiment (n = 6 wells per condition). *P < 0.005. (F) DOCK3 overexpression fails to induce active RAC1 (RAC1-GTP) in normal and DMD primary myotubes overexpressing either HA-DOCK3 or a control vector. Western blot images of other RAC1 downstream signaling factors (CDC42 and RHOA), DOCK3, and a β-actin–loading control are also shown.