MicroRNA-208a is a regulator of cardiac hypertrophy and conduction in mice
Thomas E. Callis, Kumar Pandya, Hee Young Seok, Ru-Hang Tang, Mariko Tatsuguchi, Zhan-Peng Huang, Jian-Fu Chen, Zhongliang Deng, Bronwyn Gunn, Janelle Shumate, Monte S. Willis, Craig H. Selzman, Da-Zhi Wang
Thomas E. Callis, Kumar Pandya, Hee Young Seok, Ru-Hang Tang, Mariko Tatsuguchi, Zhan-Peng Huang, Jian-Fu Chen, Zhongliang Deng, Bronwyn Gunn, Janelle Shumate, Monte S. Willis, Craig H. Selzman, Da-Zhi Wang
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Research Article Cardiology

MicroRNA-208a is a regulator of cardiac hypertrophy and conduction in mice

Abstract

MicroRNAs (miRNAs) are a class of small noncoding RNAs that have gained status as important regulators of gene expression. Here, we investigated the function and molecular mechanisms of the miR-208 family of miRNAs in adult mouse heart physiology. We found that miR-208a, which is encoded within an intron of α-cardiac muscle myosin heavy chain gene (Myh6), was actually a member of a miRNA family that also included miR-208b, which was determined to be encoded within an intron of β-cardiac muscle myosin heavy chain gene (Myh7). These miRNAs were differentially expressed in the mouse heart, paralleling the expression of their host genes. Transgenic overexpression of miR-208a in the heart was sufficient to induce hypertrophic growth in mice, which resulted in pronounced repression of the miR-208 regulatory targets thyroid hormone–associated protein 1 and myostatin, 2 negative regulators of muscle growth and hypertrophy. Studies of the miR-208a Tg mice indicated that miR-208a expression was sufficient to induce arrhythmias. Furthermore, analysis of mice lacking miR-208a indicated that miR-208a was required for proper cardiac conduction and expression of the cardiac transcription factors homeodomain-only protein and GATA4 and the gap junction protein connexin 40. Together, our studies uncover what we believe are novel miRNA-dependent mechanisms that modulate cardiac hypertrophy and electrical conduction.

Authors

Thomas E. Callis, Kumar Pandya, Hee Young Seok, Ru-Hang Tang, Mariko Tatsuguchi, Zhan-Peng Huang, Jian-Fu Chen, Zhongliang Deng, Bronwyn Gunn, Janelle Shumate, Monte S. Willis, Craig H. Selzman, Da-Zhi Wang

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Figure 8

miR-208a is required for proper expression of gap junction protein connexin 40 and cardiac transcription factors GATA4 and Hop.

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miR-208a is required for proper expression of gap junction protein conne...
(A and B) Transcripts for Cx43 were detected by real-time PCR in hearts from (A) miR-208a Tg and control mice (n = 5/genotype) and (B) wild-type and Mir208a–/– mice (n = 5/genotype). (C and D) Transcripts for Cx40 were detected in hearts from (C) miR-208a Tg and control mice (n = 5 each genotype) and (D) wild-type and Mir208a–/– mice (n = 5/genotype). Values in A–D are presented as the fold change in expression ± SEM. *P < 0.01. (E) Western blotting for Cx40 proteins using hearts from 4-month-old wild-type and Mir208a–/– mice. β-Tubulin served as a loading control. (F) Transcripts for Hop were detected by real-time PCR in hearts from wild-type and Mir208a–/– mice (n = 5/genotype). (G) Western blotting for Hop proteins using hearts from 4-month-old wild-type and Mir208a–/– mice. (H) 293T cells were transfected with a luciferase reporter designed to detect miR-208a expression and with miRNA expression plasmids, and luciferase activity was determined. A luciferase reporter with 4 repeats of the putative miR-208a binding site was also cotransfected with miRNA expression plasmids and luciferase activity determined. Values are mean luciferase activity ± SD relative to the luciferase activity of reporters cotransfected with empty expression plasmid. (I) Western blotting for GATA4 proteins using hearts from 4-month-old wild-type and Mir208a–/– mice. **P < 0.05.