背景:MRPS36基因编码最近鉴定的2-氧戊二酸脱氢酶复合物(OGDHC)的成分,Krebs循环的关键酶,催化2-氧戊二酸氧化脱羧为琥珀酰辅酶A。OGDHC活性缺陷会导致临床上可变的代谢紊乱,其特征是整体发育迟缓,严重的神经损伤,肝功能衰竭,和早发性乳酸性酸中毒。
方法:我们通过外显子组测序研究了两个兄弟姐妹的Leigh综合征伴双侧纹状体坏死的分子原因。功能研究包括测量成纤维细胞中的OGDHC酶活性和MRPS36mRNA水平,转染细胞中蛋白质稳定性的评估,和结构分析。进行文献综述以确定OGDHC缺乏症的病因和表型谱。
结果:在两个受影响的兄弟中,外显子组测序鉴定出一个纯合无义变体(c.283G>T,MRPS36的p.Glu95*)。该变体不影响转录本加工和稳定性,也没有蛋白质水平,但导致缺乏9个残基的较短蛋白质,这些残基有助于OGDHC复合物的结构和功能组织。OGDHC酶活性显著降低。对先前报道的OGDHC缺乏症病例的回顾支持了这种酶促缺陷与Leigh表型谱和早发性运动障碍的关联。在我们和文献中患有OGDHC缺陷的患者中观察到血浆谷氨酸和谷氨酰胺水平略有升高。
结论:我们的发现指出MRPS36是一种新的致病基因,与Leigh综合征有关。在OGDHC缺乏症患者中观察到的血浆谷氨酸和谷氨酰胺水平的轻微升高代表了这种神经代谢紊乱的候选代谢特征。©2024国际帕金森和运动障碍协会。
BACKGROUND: The MRPS36 gene encodes a recently identified component of the 2-oxoglutarate dehydrogenase complex (OGDHC), a key enzyme of the Krebs cycle catalyzing the oxidative decarboxylation of 2-oxoglutarate to succinyl-CoA. Defective OGDHC activity causes a clinically variable metabolic disorder characterized by global developmental delay, severe neurological impairment, liver failure, and early-onset lactic acidosis.
METHODS: We investigated the molecular cause underlying Leigh syndrome with bilateral striatal necrosis in two siblings through exome sequencing. Functional studies included measurement of the OGDHC enzymatic activity and MRPS36 mRNA levels in fibroblasts, assessment of protein stability in transfected cells, and structural analysis. A literature review was performed to define the etiological and phenotypic spectrum of OGDHC deficiency.
RESULTS: In the two affected brothers, exome sequencing identified a homozygous nonsense variant (c.283G>T, p.Glu95*) of MRPS36. The variant did not affect transcript processing and stability, nor protein levels, but resulted in a shorter protein lacking nine residues that contribute to the structural and functional organization of the OGDHC complex. OGDHC enzymatic activity was significantly reduced. The review of previously reported cases of OGDHC deficiency supports the association of this enzymatic defect with Leigh phenotypic spectrum and early-onset movement disorder. Slightly elevated plasma levels of glutamate and glutamine were observed in our and literature patients with OGDHC defect.
CONCLUSIONS: Our findings point to MRPS36 as a new disease gene implicated in Leigh syndrome. The slight elevation of plasma levels of glutamate and glutamine observed in patients with OGDHC deficiency represents a candidate metabolic signature of this neurometabolic disorder. © 2024 International Parkinson and Movement Disorder Society.