Department of Molecular Microbiology and Immunology, School of Medicine, The University of Missouri, Columbia, MO, 65212, USA.
Department of Neurology, School of Medicine, The University of Missouri, Columbia, MO, 65212, USA.
BMC Musculoskelet Disord. 2024 Oct 14;25(1):811. doi: 10.1186/s12891-024-07927-8.
Cytosolic calcium overload contributes to muscle degradation in Duchenne muscular dystrophy (DMD). The sarcoplasmic reticulum (SR) is the primary calcium storage organelle in muscle. The sarco-endoplasmic reticulum ATPase (SERCA) pumps cytosolic calcium to the SR during muscle relaxation. Calcium is kept in the SR by calcium-binding proteins.
Given the importance of the canine DMD model in translational studies, we examined transcriptional changes of SERCA (SERCA1 and SERCA2a), SERCA regulators (phospholamban, sarcolipin, myoregulin, and dwarf open reading frame), and SR calcium-binding proteins (calreticulin, calsequestrin 1, calsequestrin 2, and sarcalumenin) in skeletal muscle (diaphragm and extensor carpi ulnaris) and heart (left ventricle) in normal and affected male dogs by droplet digital PCR before the onset (≤ 2-m-old), at the active stage (8 to 16-m-old), and at the terminal stage (30 to 50-m-old) of the disease. Since many of these proteins are expressed in a fiber type-specific manner, we also evaluated fiber type composition in skeletal muscle.
In affected dog skeletal muscle, SERCA and its regulators were down-regulated at the active stage, but calcium-binding proteins (except for calsequestrin 1) were upregulated at the terminal stage. Surprisingly, nominal differences were detected in the heart. We also examined whether there exists sex-biased expression in 8 to 16-m-old dogs. Multiple transcripts were significantly downregulated in the heart and extensor carpi ulnaris muscle of female dogs. In fiber type analysis, we found significantly more type I fiber in the diaphragm of 8 to 16-m-old affected dogs, and significantly more type II fibers in the extensor carpi ulnaris of 30 to 50-m-old affected dogs. However, no difference was detected between male and female dogs.
Our study adds new knowledge to the understanding of muscle calcium regulation in normal and dystrophic canines.
细胞质钙超载是杜氏肌营养不良症（DMD）肌肉退化的原因之一。肌浆网（SR）是肌肉中主要的钙储存细胞器。在肌肉松弛时，肌浆网 Ca2+-ATP 酶（SERCA）将细胞质中的 Ca2+泵入肌浆网。钙结合蛋白将 Ca2+保持在肌浆网中。
鉴于犬 DMD 模型在转化研究中的重要性，我们通过液滴数字 PCR 检测了正常和患病雄性犬的骨骼肌（膈肌和尺侧腕伸肌）和心脏（左心室）中 SERCA（SERCA1 和 SERCA2a）、SERCA 调节剂（肌球蛋白结合蛋白、肌浆球蛋白、肌调节蛋白和矮小开放阅读框）以及 SR 钙结合蛋白（钙网蛋白、钙调蛋白 1、钙调蛋白 2 和肌浆网钙蛋白）的转录变化，在疾病的起始前（≤2 月龄）、活跃期（8 至 16 月龄）和终末期（30 至 50 月龄）。由于许多这些蛋白以纤维类型特异性的方式表达，我们还评估了骨骼肌中的纤维类型组成。
在患病犬的骨骼肌中，SERCA 及其调节剂在活跃期下调，但钙结合蛋白（除钙调蛋白 1 外）在终末期上调。令人惊讶的是，在心脏中检测到名义上的差异。我们还检查了 8 至 16 月龄的犬是否存在性别偏向表达。在雌性犬的心脏和尺侧腕伸肌中，多个转录本显著下调。在纤维类型分析中，我们发现 8 至 16 月龄患病犬的膈肌中明显有更多的 I 型纤维，而 30 至 50 月龄患病犬的尺侧腕伸肌中明显有更多的 II 型纤维。然而，在雄性和雌性犬之间没有发现差异。
本研究为理解正常和营养不良犬的肌肉钙调节增加了新知识。
