In vivo characterization of the aspartyl-tRNA synthetase DARS: Homing in on the leukodystrophy HBSL
In vivo characterization of the aspartyl-tRNA synthetase DARS: Homing in on the leukodystrophy HBSL
复制标题
DOI：
10.1016/j.nbd.2016.10.008
复制
发表时间：
2017-01-01
影响因子：
6.1
通讯作者：
Klugmann, Matthias
中科院分区：
文献类型：
--
作者：
Frohlich, Dominik;Suchowerska, Alexandra K.;Klugmann, Matthias
背景：最近诊断的脑白质营养不良伴脑干和脊髓累及及腿部痉挛（HBSL）是由细胞质天冬氨酸- trna合成酶基因DARS突变引起的。DARS在翻译中的生理作用是准确地将天冬氨酸与其同源tRNA配对。在临床上，HBSL受试者表现出明显的髓鞘化低模式，并发展为进行性腿部痉挛、变异性认知障碍和癫痫。为了阐明潜在的病理机制，我们全面评估了小鼠内源性DARS的表达。此外，为了创建第一个哺乳动物HBSL模型，我们对具有靶向Dars位点的突变小鼠进行了基因工程和表型分型。结果：DARS虽然在所有器官中表达，但在成人大脑中表现出独特的表达模式，在大胶质细胞中几乎没有免疫反应性，但在海马、小脑和皮层的神经元亚群中富集。在神经元内，DARS主要位于细胞体中，与翻译机制的其他组成部分共定位。有趣的是，DARS也存在于神经突和突触上，在那里它可能有助于局部蛋白质合成。无dars的小鼠不能存活，在胚胎第11天前死亡。只有一个功能性Dars等位基因的杂合子小鼠大脑中的Dars水平显著降低；然而，这些突变体没有表现出明显的异常，包括运动表现不变。然而，我们在Dars（+/-）小鼠中检测到脉冲前声惊吓反应抑制减少，表明注意加工功能障碍。结论：我们的研究结果首次揭示了小鼠DARS组织分布的深入特征，揭示了大脑区域或主要神经细胞类型之间令人惊讶的一致性。DARS功能的完全丧失在小鼠中是不能耐受的，这表明在人类中鉴定的HBSL突变保留了一些残留的酶活性。杂合子DARS -null携带者的轻度表型表明，即使DARS水平的部分恢复也与治疗相关，尽管它们不像临床症状的全部谱系，但DARS（+/-）小鼠的强大的脉冲前抑制表型将有助于未来的临床前治疗疗效研究。总之，我们的数据对更好地理解DARS功能和HBSL病理有重要贡献。(C) 2016年作者。Elsevier Inc.出版。这是一篇基于CC BY-NC-ND许可的开放获取文章。
Background: The recently diagnosed leukodystrophy Hypomyelination with Brain stem and Spinal cord involvement and Leg spasticity (HBSL) is caused by mutations of the cytoplasmic aspartyl-tRNA synthetase gene DARS. The physiological role of DARS in translation is to accurately pair aspartate with its cognate tRNA. Clinically, HBSL subjects show a distinct pattern of hypomyelination and develop progressive leg spasticity, variable cognitive impairment and epilepsy. To elucidate the underlying pathomechanism, we comprehensively assessed endogenous DARS expression in mice. Additionally, aiming at creating the first mammalian HBSL model, we genetically engineered and phenotyped mutant mice with a targeted Dars locus.Results: DARS, although expressed in all organs, shows a distinct expression pattern in the adult brain with little immunoreactivity in macroglia but enrichment in neuronal subpopulations of the hippocampus, cerebellum, and cortex. Within neurons, DARS is mainly located in the cell soma where it co-localizes with other components of the translation machinery. Intriguingly, DARS is also present along neurites and at synapses, where it potentially contributes to local protein synthesis. Dars-null mice are not viable and die before embryonic day 11. Heterozygous mice with only one functional Dars allele display substantially reduced DARS levels in the brain; yet these mutants show no gross abnormalities, including unchanged motor performance. However, we detected reduced pre-pulse inhibition of the acoustic startle response indicating dysfunction of attentional processing in Dars(+/-) mice.Conclusions: Our results, for the first time, show an in-depth characterization of the DARS tissue distribution in mice, revealing surprisingly little uniformity across brain regions or between the major neural cell types. The complete loss of DARS function is not tolerated in mice suggesting that the identified HBSL mutations in humans retain some residual enzyme activity. The mild phenotype of heterozygous Dars-null carriers indicates that even partial restoration of DARS levels would be therapeutically relevant Despite the fact that they do not resemble the full spectrum of clinical symptoms, the robust pre-pulse inhibition phenotype of Dars(+/-) mice will be instrumental for future preclinical therapeutic efficacy studies. In summary, our data is an important contribution to a better understanding of DARS function and HBSL pathology. (C) 2016 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license.