PDF(Pubmed)
Abstract：
UNASSIGNED: Methylmalonic acidemia (MMA) is a rare inborn genetic disorder that is characterized by increased levels of methylmalonic acid in blood plasma and urine. Isolated methylmalonic acidemia is one of the most common types of MMA and is caused by mutations in the gene encoding methyl-malonyl coenzyme A mutase (MMUT). In this study, we investigated the possible mechanisms underlying the symptoms of isolated MMA in a patient by molecular analysis.
UNASSIGNED: PCR amplification and Sanger sequencing analysis was performed to identify variants in the MMUT gene in the proband and his family. Furthermore, minigene constructs were generated to validate the splicing defects in the MMUT gene variant identified in the proband.
UNASSIGNED: The 3-year-old patient was admitted to the hospital with symptoms of MMA, including fever, convulsions, and vomiting. He showed metabolic acidosis, high levels of methylmalonic acid in blood and urine, and normal blood homocysteine levels. Genetic analysis demonstrated that the patient was a compound heterozygous carrier of two variants in the MMUT gene: a missense c.278G > A variant that has already been reported in a patient with the severe mut⁰ phenotype; and a novel splice site variant c.2125-2A > G. RT-PCR analysis showed that, while the novel variant clearly alters splicing, a minor amount of a full-length transcript is generated, suggesting that a wild-type protein may be produced although at a lower quantitative level. The patient\'s condition improved after treatment with vitamin B12. Serious complications were not reported during follow-up at age 5.
UNASSIGNED: We identified a novel splice site variant that partially disrupts normal splicing of the MMUT pre-mRNA. Production of a reduced amount of full-length transcript is responsible for the mild clinical phenotype observed in this patient. Functional studies have proven useful in exploring the genotype-phenotype association and in providing guidance for the genetic diagnosis of MMA.
UNASSIGNED: PCR amplification and Sanger sequencing analysis was performed to identify variants in the MMUT gene in the proband and his family. Furthermore, minigene constructs were generated to validate the splicing defects in the MMUT gene variant identified in the proband.
UNASSIGNED: The 3-year-old patient was admitted to the hospital with symptoms of MMA, including fever, convulsions, and vomiting. He showed metabolic acidosis, high levels of methylmalonic acid in blood and urine, and normal blood homocysteine levels. Genetic analysis demonstrated that the patient was a compound heterozygous carrier of two variants in the MMUT gene: a missense c.278G > A variant that has already been reported in a patient with the severe mut⁰ phenotype; and a novel splice site variant c.2125-2A > G. RT-PCR analysis showed that, while the novel variant clearly alters splicing, a minor amount of a full-length transcript is generated, suggesting that a wild-type protein may be produced although at a lower quantitative level. The patient\'s condition improved after treatment with vitamin B12. Serious complications were not reported during follow-up at age 5.
UNASSIGNED: We identified a novel splice site variant that partially disrupts normal splicing of the MMUT pre-mRNA. Production of a reduced amount of full-length transcript is responsible for the mild clinical phenotype observed in this patient. Functional studies have proven useful in exploring the genotype-phenotype association and in providing guidance for the genetic diagnosis of MMA.
摘要：
■甲基丙二酸血症（MMA）是一种罕见的先天性遗传性疾病，其特征是血浆和尿液中甲基丙二酸水平升高。分离的甲基丙二酸血症是最常见的MMA类型之一，由编码甲基丙二酰辅酶A变位酶（MMUT）的基因突变引起。在这项研究中,我们通过分子分析研究了患者中孤立性MMA症状的可能机制.
■进行PCR扩增和Sanger测序分析，以鉴定先证者及其家族中MMUT基因的变体。此外，产生小基因构建体以验证在先证中鉴定的MMUT基因变体中的剪接缺陷。
这名3岁的患者因MMA症状入院，包括发烧,抽搐,和呕吐。他表现出代谢性酸中毒,血液和尿液中甲基丙二酸含量高,和正常的血同型半胱氨酸水平。遗传分析表明，该患者是MMUT基因中两个变体的复合杂合携带者：一个错义c.278G>A变体，该变体已在患有严重mut表型的患者中报道；以及一个新的剪接位点变体c.2125-2A>G。RT-PCR分析表明，虽然新的变体明显改变了剪接，产生少量的全长转录本，这表明尽管在较低的定量水平下仍可能产生野生型蛋白质。患者的病情在接受维生素B12治疗后得到改善。在5岁时随访期间未报告严重并发症。
■我们鉴定了一种新的剪接位点变体，该变体部分破坏了MMUT前mRNA的正常剪接。减少量的全长转录物的产生是在该患者中观察到的轻度临床表型的原因。功能研究已被证明可用于探索基因型-表型关联并为MMA的遗传诊断提供指导。
■进行PCR扩增和Sanger测序分析，以鉴定先证者及其家族中MMUT基因的变体。此外，产生小基因构建体以验证在先证中鉴定的MMUT基因变体中的剪接缺陷。
这名3岁的患者因MMA症状入院，包括发烧,抽搐,和呕吐。他表现出代谢性酸中毒,血液和尿液中甲基丙二酸含量高,和正常的血同型半胱氨酸水平。遗传分析表明，该患者是MMUT基因中两个变体的复合杂合携带者：一个错义c.278G>A变体，该变体已在患有严重mut表型的患者中报道；以及一个新的剪接位点变体c.2125-2A>G。RT-PCR分析表明，虽然新的变体明显改变了剪接，产生少量的全长转录本，这表明尽管在较低的定量水平下仍可能产生野生型蛋白质。患者的病情在接受维生素B12治疗后得到改善。在5岁时随访期间未报告严重并发症。
■我们鉴定了一种新的剪接位点变体，该变体部分破坏了MMUT前mRNA的正常剪接。减少量的全长转录物的产生是在该患者中观察到的轻度临床表型的原因。功能研究已被证明可用于探索基因型-表型关联并为MMA的遗传诊断提供指导。
