PDF(Pubmed)
Abstract：
Kinesin family member 5A (KIF5A) is an essential, neuron-specific microtubule-associated motor protein responsible for the anterograde axonal transport of various cellular cargos. Loss of function variants in the N-terminal, microtubule-binding domain are associated with hereditary spastic paraplegia and hereditary motor neuropathy. These variants result in a loss of the ability of the mutant protein to process along microtubules. Contrastingly, gain of function splice-site variants in the C-terminal, cargo-binding domain of KIF5A are associated with amyotrophic lateral sclerosis (ALS), a neurodegenerative disease involving death of upper and lower motor neurons, ultimately leading to degradation of the motor unit (MU; an alpha motor neuron and all the myofibers it innervates) and death. These ALS-associated variants result in loss of autoinhibition, increased procession of the mutant protein along microtubules, and altered cargo binding. To study the molecular and cellular consequences of ALS-associated variants in vivo, we introduced the murine homolog of an ALS-associated KIF5A variant into C57BL/6 mice using CRISPR-Cas9 gene editing which produced mutant Kif5a mRNA and protein in neuronal tissues of heterozygous (Kif5a+/c.3005+1G>A; HET) and homozygous (Kif5ac.3005+1G>A/c.3005+1G>A; HOM) mice. HET and HOM mice appeared normal in behavioral and electrophysiological (compound muscle action potential [CMAP] and MU number estimation [MUNE]) outcome measures at one year of age. When subjected to sciatic nerve injury, HET and HOM mice have delayed and incomplete recovery of the MUNE compared to wildtype (WT) mice suggesting an impairment in MU repair. Moreover, aged mutant Kif5a mice (aged two years) had reduced MUNE independent of injury, and exacerbation of the delayed and incomplete recovery after injury compared to aged WT mice. These data suggest that ALS-associated variants may result in an impairment of the MU to respond to biological challenges such as injury and aging, leading to a failure of MU repair and maintenance. In this report, we present the behavioral, electrophysiological and pathological characterization of mice harboring an ALS-associated Kif5a variant to understand the functional consequences of KIF5A C-terminal variants in vivo.
摘要：
Kinesin家族成员5A(KIF5A)是必不可少的，神经元特异性微管相关运动蛋白，负责各种细胞货物的顺行轴突运输。N端功能变体的丢失，微管结合域与遗传性痉挛性截瘫和遗传性运动神经病有关。这些变体导致突变蛋白沿微管加工的能力丧失。相反，在C末端获得功能剪接位点变体，KIF5A的货物结合域与肌萎缩侧索硬化症（ALS）相关，一种涉及上下运动神经元死亡的神经退行性疾病，最终导致运动单位（MU；α运动神经元及其支配的所有肌纤维）退化和死亡。这些ALS相关变体导致自身抑制的丧失，沿着微管的突变蛋白的增加，和改变货物绑定。为了研究体内ALS相关变体的分子和细胞后果，我们使用CRISPR-Cas9基因编辑将ALS相关KIF5A变体的鼠同源物引入C57BL/6小鼠中,该基因编辑在杂合(Kif5a+/c.3005+1G>A;HET)和纯合(Kif5ac.3005+1G>A/c.3005+1G>A;HOM)小鼠的神经元组织中产生突变Kif5amRNA和蛋白。HET和HOM小鼠在1岁时的行为和电生理（复合肌肉动作电位[CMAP]和MU数量估计[MUNE]）结果测量中表现正常。当受到坐骨神经损伤时，与野生型（WT）小鼠相比，HET和HOM小鼠的MUNE恢复延迟且不完全恢复，表明MU修复受损。此外，年龄突变的Kif5a小鼠（两岁）的MUNE降低，而与损伤无关，与老年WT小鼠相比，损伤后延迟和不完全恢复的恶化。这些数据表明，ALS相关变体可能导致MU受损，以应对诸如损伤和衰老等生物学挑战。导致MU维修和保养失败。在这份报告中,我们呈现行为，具有ALS相关Kif5a变体的小鼠的电生理和病理学表征，以了解KIF5AC末端变体在体内的功能后果。
