Dihydrofolate Reductase Deficiency Due to a Homozygous DHFR Mutation Causes Megaloblastic Anemia and Cerebral Folate Deficiency Leading to Severe Neurologic Disease
Dihydrofolate Reductase Deficiency Due to a Homozygous DHFR Mutation Causes Megaloblastic Anemia and Cerebral Folate Deficiency Leading to Severe Neurologic Disease
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DOI：
10.1016/j.ajhg.2011.01.007
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发表时间：
2011-02-11
影响因子：
9.8
通讯作者：
Schwarz, Klaus
中科院分区：
文献类型：
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作者：
Cario, Holger;Smith, Desiree E. C.;Schwarz, Klaus
叶酸代谢先天障碍或叶酸缺乏引起的症状和并发症的严重程度说明了细胞内叶酸代谢的重要性。我们检查了三个健康的远亲父母的孩子，他们患有巨幼细胞性贫血和脑叶酸缺乏症，导致神经疾病，并伴有非典型的儿童失神癫痫。全基因组纯合图谱显示在5号染色体上有一个候选区域，包括二氢叶酸还原酶(DHFR)基因。DHFR测序显示，在所有兄弟姐妹中，都存在纯合子DHFR突变，c.458A>；T(p.Asp153Val)。用液相色谱-串联质谱仪分析患者红细胞、血浆和脑脊液中的叶酸分布，符合DHFR缺乏症。在EBV永生化的淋巴母细胞中，所有患者的DHFR活性和荧光素标记的甲氨蝶呤(FMTX)结合严重降低。杂合子细胞表现出中等的DHFR活性和FMTX结合。RT-PCR显示野生型和携带DHFR突变的细胞之间没有差异，而在DHFR突变的细胞中蛋白质表达减少。用叶酸治疗后，血液异常得到缓解，脑脊液叶酸水平恢复正常，神经症状得到改善。总而言之，DHFR纯合子突变p.Asp153Val导致DHFR缺乏，并导致一种可以用叶酸成功治疗的复杂的血液和神经疾病。DHFR对于维持足够的脑脊液和红细胞叶酸水平是必要的，即使在营养叶酸供应充足和血浆叶酸正常的情况下也是如此。
The importance of intracellular folate metabolism is illustrated by the severity of symptoms and complications caused by inborn disorders of folate metabolism or by folate deficiency. We examined three children of healthy, distantly related parents presenting with megaloblastic anemia and cerebral folate deficiency causing neurologic disease with atypical childhood absence epilepsy. Genome-wide homozygosity mapping revealed a candidate region on chromosome 5 including the dihydrofolate reductase (DHFR) locus. DHFR sequencing revealed a homozygous DHFR mutation, c.458A>T (p.Asp153Val), in all siblings. The patients' folate profile in red blood cells (RBC), plasma, and cerebrospinal fluid (CSF), analyzed by liquid chromatography tandem mass spectrometry, was compatible with DHFR deficiency. DHFR activity and fluorescein-labeled methotrexate (FMTX) binding were severely reduced in EBV-immortalized lymphoblastoid cells of all patients. Heterozygous cells displayed intermediate DHFR activity and FMTX binding. RT-PCR of DHFR mRNA revealed no differences between wild-type and DHFR mutation-carrying cells, whereas protein expression was reduced in cells with the DHFR mutation. Treatment with folinic acid resulted in the resolution of hematological abnormalities, normalization of CSF folate levels, and improvement of neurological symptoms. In conclusion, the homozygous DHFR mutation p.Asp153Val causes DHFR deficiency and leads to a complex hematological and neurological disease that can be successfully treated with folinic acid. DHFR is necessary for maintaining sufficient CSF and RBC folate levels, even in the presence of adequate nutritional folate supply and normal plasma folate.