Investigating how Mylpf-regulated sarcomere formation influences limb skeletal development

研究 Mylpf 调节的肌节形成如何影响肢体骨骼发育 在关节挛缩症中，婴儿出生时至少有两个肢体，手或脚出现挛缩；最 通常表现为马蹄内翻足，大约每 4000 名活产儿中就有 1 人患有此病。关节弯曲导致受损 运动，可能需要终生进行多次手术才能纠正。该病的特点是 骨骼关节缺陷，但它是由子宫内肌肉运动受损引起的。我们最近发现 肌肉表达基因 Mylpf 不仅对于正常的肌动蛋白运动至关重要，而且对于肌纤维的完整性和 人类 MYLPF 的变异导致 1 型远端关节弯曲 (DA1)。 Mylpf 蛋白与肌球蛋白结合 头部区域附近的重链在肌肉收缩期间移动肌动蛋白。我们发现斑马鱼 mylpfa 突变幼虫表现出与 DA1 一致的表型，包括肌球蛋白活性受损、肌球蛋白活性降低、 肌肉力量全面，鳍完全麻痹。令人惊讶的是，我们发现 Mylpf 函数不仅需要 正常收缩，还用于将肌动蛋白和肌球蛋白组装成肌肉的基本单位，称为 肌节。在未发表的工作中，我们发现 mylpfa 突变体中的肌节形成很差，缺乏以下两种之一 Mylpf 基因在 mylpfa;mylpfb 双突变体中完全缺失，缺乏所有 Mylpf 功能。我们 假设 Mylpf 功能通过促进肌节的结合来预防远端关节弯曲 肢体关节形成时胚胎发育关键窗口期间的成分。为了测试这个 假设，我们将（目标 1）研究 Mylpf 在肌节组装中的作用，（目标 2a）研究 Mylpf 如何 人类 MYLPF 基因变异会导致这种肌肉骨骼疾病，并且（目标 2b）当骨骼缺陷可以 予以纠正。

Investigating how Mylpf-regulated sarcomere formation influences limb skeletal development In arthrogryposis, babies are born with at least two limbs with hand or foot showing contractures; it most commonly manifests as clubfoot, and it is found in roughly 1 in 4000 live births. Arthrogryposis causes impaired movement and can require many surgeries through a lifetime to correct. The disease is characterized by skeletal joint defects, but it is caused by impaired muscle movement in utero. We recently found that the muscle-expressed gene Mylpf is vital not only to normal actin movement, but also for muscle fiber integrity and that variants in human MYLPF cause Distal Arthrogryposis Type 1 (DA1). Mylpf protein binds to the myosin heavy chain near head region which moves actin during muscle contraction. We discovered that zebrafish mylpfa mutant larvae display a phenotype consistent with DA1, including impaired myosin activity, reduced muscle force overall, and complete fin paralysis. Surprisingly, we find that Mylpf function is needed not only for normal contraction, but also for the assembly of actin and myosin into the fundamental unit of muscle, called sarcomeres. In unpublished work we find that sarcomeres form poorly in mylpfa mutants, lacking one of two Mylpf genes, and are completely absent in mylpfa;mylpfb double mutants, which lack all Mylpf function. We hypothesize that Mylpf function prevents distal arthrogryposis by promoting association of sarcomeric components during the critical window of embryonic development when limb joints are forming. To test this hypothesis, we will (Aim 1) investigate the role of Mylpf in sarcomere assembly, (Aim 2a) investigate how the human MYLPF gene variants cause this musculo-skeletal disease, and (Aim 2b) when the skeletal defects can be corrected.