Mignani Luca, Zizioli Daniela, Borsani Giuseppe, Monti Eugenio, Finazzi Dario
Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy.
Laboratory of Clinical Chemistry, Azienda Socio Sanitaria Territoriale (ASST) Spedali Civili di Brescia, Brescia, Italy.
Front Cell Dev Biol. 2020 Dec 23;8:596069. doi: 10.3389/fcell.2020.596069. eCollection 2020.
Mitochondrial membrane Protein Associated Neurodegeneration (MPAN) is a rare genetic disorder due to mutations in gene. In most cases, the disorder is transmitted as an autosomal recessive trait and the main clinical features are progressive spastic para/tetraparesis, dystonia, motor axonal neuropathy, parkinsonisms, psychiatric symptoms, and optic atrophy. Besides iron accumulation in the globus pallidus and substantia nigra, the neuropathology shows features also observed in Parkinson's Disease brains, such as α-synuclein-positive Lewy bodies and hyperphosphorylated tau. Mutations in the gene have been found in other neurodegenerative disorders, including PD, hereditary spastic paraplegia, pallido-pyramidal syndrome, and amyotrophic lateral sclerosis. The biological function of gene is poorly defined. In humans, it codes for two protein isoforms: the longer one is present in mitochondria, endoplasmic reticulum, and contact regions between mitochondria and ER. Mutations in the gene appear to be linked to defects in mitochondrial activity, lipid metabolism and autophagy/mitophagy. To increase the available tools for the investigation of MPAN pathogenesis, we generated a new animal model in zebrafish embryos. The zebrafish genome contains four co-orthologs of human . One of them, located on chromosome 18, is expressed at higher levels at early stages of development. We downregulated its expression by microinjecting embryos with a specific ATG-blocking morpholino, and we analyzed embryonal development. Most embryos showed morphological defects such as unsettled brain morphology, with smaller head and eyes, reduced yolk extension, tilted and thinner tail. The severity of the defects progressively increased and all injected embryos died within 7 days post fertilization. Appropriate controls confirmed the specificity of the observed phenotype. Changes in the expression and distribution of neural markers documented a defective neuronal development, particularly evident in the eyes, the optic tectum, the midbrain-hindbrain boundary; Rohon Beard and dorsal root ganglia neurons were also affected. Phalloidin staining evidenced a significant perturbation of musculature formation that was associated with defective locomotor behavior. These data are consistent with the clinical features of MPAN and support the validity of the model to investigate the pathogenesis of the disease and evaluate molecules with potential therapeutic effect.
线粒体膜蛋白相关神经变性（MPAN）是一种由基因突变引起的罕见遗传疾病。在大多数情况下，该疾病以常染色体隐性遗传特征传递，主要临床特征为进行性痉挛性截瘫/四肢瘫、肌张力障碍、运动轴索性神经病、帕金森综合征、精神症状和视神经萎缩。除了苍白球和黑质中铁的蓄积外，神经病理学表现还见于帕金森病大脑，如α-突触核蛋白阳性路易小体和过度磷酸化的tau蛋白。该基因的突变也见于其他神经退行性疾病，包括帕金森病、遗传性痉挛性截瘫、苍白球-锥体综合征和肌萎缩侧索硬化症。该基因的生物学功能尚不清楚。在人类中，它编码两种蛋白质异构体：较长的一种存在于线粒体、内质网以及线粒体与内质网的接触区域。该基因的突变似乎与线粒体活性、脂质代谢和自噬/线粒体自噬缺陷有关。为了增加研究MPAN发病机制的可用工具，我们在斑马鱼胚胎中建立了一种新的动物模型。斑马鱼基因组包含人类该基因的四个共直系同源基因。其中一个位于18号染色体上，在发育早期表达水平较高。我们通过向胚胎显微注射特异性的ATG阻断吗啉代寡核苷酸来下调其表达，并分析胚胎发育情况。大多数胚胎表现出形态学缺陷，如脑形态不稳定、头和眼睛较小、卵黄延伸减少、尾巴倾斜且变细。缺陷的严重程度逐渐增加，所有注射的胚胎在受精后7天内死亡。适当的对照证实了所观察到的表型的特异性。神经标志物表达和分布的变化记录了神经元发育缺陷，在眼睛、视顶盖、中脑-后脑边界尤为明显；罗霍恩·比尔神经元和背根神经节神经元也受到影响。鬼笔环肽染色证明肌肉组织形成受到显著干扰，这与运动行为缺陷有关。这些数据与MPAN的临床特征一致，并支持该模型在研究疾病发病机制和评估具有潜在治疗作用的分子方面的有效性。
