Department of Cell Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, United States of America.
PLoS One. 2011 Apr 26;6(4):e19274. doi: 10.1371/journal.pone.0019274.
CUG-BP and ETR-3-like factor (CELF) proteins regulate tissue- and developmental stage-specific alternative splicing in striated muscle. We previously demonstrated that heart muscle-specific expression of a nuclear dominant negative CELF protein in transgenic mice (MHC-CELFΔ) effectively disrupts endogenous CELF activity in the heart in vivo, resulting in impaired cardiac function. In this study, transgenic mice that express the dominant negative protein under a skeletal muscle-specific promoter (Myo-CELFΔ) were generated to investigate the role of CELF-mediated alternative splicing programs in normal skeletal muscle.
METHODOLOGY/PRINCIPAL FINDINGS: Myo-CELFΔ mice exhibit modest changes in CELF-mediated alternative splicing in skeletal muscle, accompanied by a reduction of endomysial and perimysial spaces, an increase in fiber size variability, and an increase in slow twitch muscle fibers. Weight gain and mean body weight, total number of muscle fibers, and overall muscle strength were not affected.
CONCLUSIONS/SIGNIFICANCE: Although these findings demonstrate that CELF activity contributes to the normal alternative splicing of a subset of muscle transcripts in vivo, the mildness of the effects in Myo-CELFΔ muscles compared to those in MHC-CELFΔ hearts suggests CELF activity may be less determinative for alternative splicing in skeletal muscle than in heart muscle. Nonetheless, even these small changes in CELF-mediated splicing regulation were sufficient to alter muscle organization and muscle fiber properties affected in myotonic dystrophy. This lends further evidence to the hypothesis that dysregulation of CELF-mediated alternative splicing programs may be responsible for the disruption of these properties during muscle pathogenesis.
CUG-BP 和 ETR-3 样因子（CELF）蛋白调节横纹肌组织和发育阶段特异性的可变剪接。我们之前证明，在转基因小鼠中，心脏特异性表达核显性负性 CELF 蛋白（MHC-CELFΔ）可有效地在体内破坏内源性 CELF 活性，导致心脏功能受损。在这项研究中，生成了在骨骼肌特异性启动子下表达显性负性蛋白的转基因小鼠（Myo-CELFΔ），以研究 CELF 介导的可变剪接程序在正常骨骼肌中的作用。
方法/主要发现：Myo-CELFΔ 小鼠的骨骼肌中 CELF 介导的可变剪接发生了轻微变化，伴随肌内膜和肌周膜空间减少，纤维大小变异性增加，慢肌纤维增加。体重增加和平均体重、肌纤维总数和整体肌肉力量不受影响。
结论/意义：尽管这些发现表明 CELF 活性有助于体内正常的骨骼肌亚群转录物的可变剪接，但与 MHC-CELFΔ 心脏相比，Myo-CELFΔ 肌肉中的作用较温和，表明 CELF 活性对骨骼肌的可变剪接的决定性可能不如对心肌。尽管如此，即使是 CELF 介导的剪接调节的这些微小变化也足以改变肌肉组织和肌肉纤维特性，这些特性在肌强直性营养不良中受到影响。这进一步证明了假说，即 CELF 介导的可变剪接程序的失调可能是导致肌肉发病过程中这些特性破坏的原因。
