Animal Genomics Laboratory, UCD School of Agriculture, Food Science and Veterinary Medicine, UCD College of Life Sciences, University College Dublin, Belfield, Dublin 4, Ireland.
BMC Genomics. 2009 Dec 30;10:638. doi: 10.1186/1471-2164-10-638.
Selection for exercise-adapted phenotypes in the Thoroughbred racehorse has provided a valuable model system to understand molecular responses to exercise in skeletal muscle. Exercise stimulates immediate early molecular responses as well as delayed responses during recovery, resulting in a return to homeostasis and enabling long term adaptation. Global mRNA expression during the immediate-response period has not previously been reported in skeletal muscle following exercise in any species. Also, global gene expression changes in equine skeletal muscle following exercise have not been reported. Therefore, to identify novel genes and key regulatory pathways responsible for exercise adaptation we have used equine-specific cDNA microarrays to examine global mRNA expression in skeletal muscle from a cohort of Thoroughbred horses (n = 8) at three time points (before exercise, immediately post-exercise, and four hours post-exercise) following a single bout of treadmill exercise.
Skeletal muscle biopsies were taken from the gluteus medius before (T(0)), immediately after (T(1)) and four hours after (T(2)) exercise. Statistically significant differences in mRNA abundance between time points (T(0) vs T(1) and T(0) vs T(2)) were determined using the empirical Bayes moderated t-test in the Bioconductor package Linear Models for Microarray Data (LIMMA) and the expression of a select panel of genes was validated using real time quantitative reverse transcription PCR (qRT-PCR). While only two genes had increased expression at T(1) (P < 0.05), by T(2) 932 genes had increased (P < 0.05) and 562 genes had decreased expression (P < 0.05). Functional analysis of genes differentially expressed during the recovery phase (T(2)) revealed an over-representation of genes localized to the actin cytoskeleton and with functions in the MAPK signalling, focal adhesion, insulin signalling, mTOR signaling, p53 signaling and Type II diabetes mellitus pathways. At T(1), using a less stringent statistical approach, we observed an over-representation of genes involved in the stress response, metabolism and intracellular signaling. These findings suggest that protein synthesis, mechanosensation and muscle remodeling contribute to skeletal muscle adaptation towards improved integrity and hypertrophy.
This is the first study to characterize global mRNA expression profiles in equine skeletal muscle using an equine-specific microarray platform. Here we reveal novel genes and mechanisms that are temporally expressed following exercise providing new knowledge about the early and late molecular responses to exercise in the equine skeletal muscle transcriptome.
在纯血马的运动适应表型选择中，提供了一个有价值的模型系统来了解骨骼肌对运动的分子反应。运动刺激即时早期的分子反应以及恢复期间的延迟反应，导致恢复到体内平衡并实现长期适应。以前在任何物种的运动后，骨骼肌中都没有报道过即时反应期间的整体 mRNA 表达。此外，也没有报道过运动后马骨骼肌的整体基因表达变化。因此，为了确定负责运动适应的新基因和关键调节途径，我们使用马特异性 cDNA 微阵列检查了来自一群纯血马（n = 8）在跑步机运动后三个时间点（运动前（T（0））、运动后即刻（T（1））和运动后 4 小时（T（2）））的骨骼肌中的整体 mRNA 表达。
在运动前（T（0））、运动后即刻（T（1））和运动后 4 小时（T（2））时，从臀中肌采集骨骼肌活检。使用经验贝叶斯调节 t 检验（Bioconductor 包 Linear Models for Microarray Data（LIMMA）中的）确定时间点之间（T（0）与 T（1）和 T（0）与 T（2））mRNA 丰度的统计学差异，使用实时定量逆转录 PCR（qRT-PCR）验证了一组选定基因的表达。虽然只有两个基因在 T（1）时表达增加（P < 0.05），但到 T（2）时，有 932 个基因表达增加（P < 0.05），562 个基因表达减少（P < 0.05）。恢复阶段（T（2））差异表达基因的功能分析显示，肌动蛋白细胞骨架定位和 MAPK 信号、焦点粘附、胰岛素信号、mTOR 信号、p53 信号和 II 型糖尿病途径中功能的基因过度表达。在 T（1）时，使用较不严格的统计方法，我们观察到应激反应、代谢和细胞内信号转导中涉及的基因的过度表达。这些发现表明，蛋白质合成、机械感觉和肌肉重塑有助于骨骼肌适应，改善完整性和肥大。
这是首次使用马特异性微阵列平台描述马骨骼肌中整体 mRNA 表达谱的研究。在这里，我们揭示了新的基因和机制，这些基因和机制在运动后按时间表达，为马骨骼肌转录组中运动的早期和晚期分子反应提供了新的知识。
