Gene expression from Prep1-ablated mice

The homeodomain transcription factor Prep1 was previously shown to regulate insulin sensitivity. Our aim was to study the specific role of Prep1 for the regulation of energy metabolism in skeletal muscle. Muscle specific ablation of Prep1 resulted in increased expression of respiratory chain subunits. This finding was consistent with an increase in mitochondrial enzyme activity without affecting mitochondrial volume fraction as assessed by electron microscopy. Metabolic phenotyping revealed no differences in daily energy expenditure or body composition. However, during treadmill exercise challenge, Prep1 ablation resulted in a higher maximal oxidative capacity and better endurance. Elevated PGC-1alpha expression was identified as a cause for increased mitochondrial capacity in Prep1-ablated mice. Prep1 stabilizes p160 Mybbp1a, a known inhibitor of PGC-1alpha activity. Thereby, P160 protein levels were significantly lower in muscle of Prep1-ablated mice. By a ChIPseq approach, PREP1-binding sites in genes encoding mitochondrial components (e.g. Ndufs2) were identified that might be responsible for elevated OXPHOS proteins in the muscle of Prep1 null mutants. These results suggest that Prep1 exhibits additional direct effects on regulation of mitochondrial proteins. We therefore conclude that Prep1 is a regulator of oxidative phosphorylation components via direct and indirect mechanisms. Consequence of Prep1 ablation in skeletal muscle was investigated in Prep1deltaSM mice and compared to Prep1 flox mice, both on C57BL/6 background. 4 mice of each genotype were used to extract RNA from the tibialis anterior muscle.同源域转录因子Prep1（homeodomain transcription factor Prep1）此前已被证实可调控胰岛素敏感性。本研究旨在探究Prep1在骨骼肌能量代谢调控中的特异性作用。骨骼肌特异性敲除Prep1可导致呼吸链亚基的表达水平升高，该结果与线粒体酶活性增强相一致，且不会改变经电子显微镜检测得到的线粒体容积分数。代谢表型分析显示，小鼠的每日能量消耗或身体成分未观察到显著差异。然而在跑台运动负荷实验中，Prep1敲除小鼠的最大氧化能力更高、耐力更优。研究证实，过氧化物酶体增殖物激活受体γ辅激活因子1α（PGC-1alpha）表达升高是Prep1敲除小鼠线粒体功能增强的诱因。Prep1可稳定p160 Mybbp1a——一种已知的PGC-1α活性抑制剂，因此Prep1敲除小鼠的肌肉组织中p160蛋白水平显著降低。通过染色质免疫共沉淀测序（ChIP-seq）技术，研究人员鉴定出线粒体组分编码基因（如Ndufs2）上的PREP1结合位点，该位点可能是Prep1敲除突变小鼠肌肉中氧化磷酸化（OXPHOS）蛋白水平升高的原因。上述结果提示，Prep1对线粒体蛋白的调控存在额外的直接作用。因此本研究得出结论：Prep1可通过直接与间接双重机制调控氧化磷酸化相关组分。本研究在Prep1deltaSM小鼠中探究了骨骼肌Prep1敲除的生物学效应，并与同处于C57BL/6遗传背景的Prep1 flox小鼠进行对照。每个基因型均使用4只小鼠，从其胫前肌中提取总RNA。