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，手或脚显示挛缩; 通常表现为马蹄内翻足，大约每4000个活产婴儿中就有一个。关节弯曲导致 运动，可能需要一生中多次手术才能纠正。该疾病的特征在于 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不仅对正常的肌动蛋白运动至关重要，而且对肌纤维的完整性和 人类MYLPF的变异导致远端关节弯曲1型（DA 1）。Mylpf蛋白与肌球蛋白结合 靠近头部区域的重链，在肌肉收缩时移动肌动蛋白。我们发现斑马鱼 mylpfa突变体幼虫表现出与DA 1一致的表型，包括肌球蛋白活性受损， 全身肌肉力量和完全的鳍麻痹令人惊讶的是，我们发现Mylpf函数不仅需要用于 正常收缩，但也用于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突变体的肌节形成较差，缺少两个中的一个。 Mylpf基因，并且在缺乏所有Mylpf功能的mylpfa;mylpfb双突变体中完全不存在。我们 假设Mylpf功能通过促进肌节联合来预防远端关节弯曲 在胚胎发育的关键窗口期间，当肢体关节形成时，为了验证这一 假设，我们将（目的1）研究Mylpf在肌节组装中的作用，（目的2a）研究Mylpf在肌节组装中的作用， 人类MYLPF基因变异导致这种肌肉骨骼疾病，（目的2b）当骨骼缺陷可以 被纠正。

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 In unpublished work we find that sarcomeres form poorly in mylpfa mutants, lacking one of two Mylpf genes, and are completely absent in mylpfa;mylpfb double mutants, which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.