TY - JOUR
T1 - Myonuclear transcription is responsive to mechanical load and DNA content but uncoupled from cell size during hypertrophy
AU - Kirby, Tyler J
AU - Patel, Rooshil M
AU - McClintock, Timothy S
AU - Dupont-Versteegden, Esther E
AU - Peterson, Charlotte A
AU - McCarthy, John J
N1 - © 2016 Kirby et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).
PY - 2016/3/1
Y1 - 2016/3/1
N2 - Myofibers increase size and DNA content in response to a hypertrophic stimulus, thus providing a physiological model with which to study how these factors affect global transcription. Using 5-ethynyl uridine (EU) to metabolically label nascent RNA, we measured a sevenfold increase in myofiber transcription during early hypertrophy before a change in cell size and DNA content. The typical increase in myofiber DNA content observed at the later stage of hypertrophy was associated with a significant decrease in the percentage of EU-positive myonuclei; however, when DNA content was held constant by preventing myonuclear accretion via satellite cell depletion, both the number of transcriptionally active myonuclei and the amount of RNA generated by each myonucleus increased. During late hypertrophy, transcription did not scale with cell size, as smaller myofibers (<1000 μm(2)) demonstrated the highest transcriptional activity. Finally, transcription was primarily responsible for changes in the expression of genes known to regulate myofiber size. These findings show that resident myonuclei possess a significant reserve capacity to up-regulate transcription during hypertrophy and that myofiber transcription is responsive to DNA content but uncoupled from cell size during hypertrophy.
AB - Myofibers increase size and DNA content in response to a hypertrophic stimulus, thus providing a physiological model with which to study how these factors affect global transcription. Using 5-ethynyl uridine (EU) to metabolically label nascent RNA, we measured a sevenfold increase in myofiber transcription during early hypertrophy before a change in cell size and DNA content. The typical increase in myofiber DNA content observed at the later stage of hypertrophy was associated with a significant decrease in the percentage of EU-positive myonuclei; however, when DNA content was held constant by preventing myonuclear accretion via satellite cell depletion, both the number of transcriptionally active myonuclei and the amount of RNA generated by each myonucleus increased. During late hypertrophy, transcription did not scale with cell size, as smaller myofibers (<1000 μm(2)) demonstrated the highest transcriptional activity. Finally, transcription was primarily responsible for changes in the expression of genes known to regulate myofiber size. These findings show that resident myonuclei possess a significant reserve capacity to up-regulate transcription during hypertrophy and that myofiber transcription is responsive to DNA content but uncoupled from cell size during hypertrophy.
KW - Animals
KW - Biomechanical Phenomena
KW - Cell Nucleus/genetics
KW - Cell Size
KW - DNA/metabolism
KW - Female
KW - Gene Expression Regulation
KW - Hypertrophy/pathology
KW - Male
KW - Mice, Inbred C57BL
KW - Muscle Fibers, Skeletal/pathology
KW - Muscle, Skeletal/pathology
KW - RNA Processing, Post-Transcriptional
KW - Transcription, Genetic
U2 - https://doi.org/10.1091/mbc.E15-08-0585
DO - https://doi.org/10.1091/mbc.E15-08-0585
M3 - Article
C2 - 26764089
SN - 1059-1524
VL - 27
SP - 788
EP - 798
JO - Molecular biology of the cell
JF - Molecular biology of the cell
IS - 5
ER -