Evaluation of the MTHFR C677T allele and the MTHFR gene locus in a German spina bifida population

A number of recent studies have demonstrated that the occurrence and recurrence risk of neural tube defects (NTD) is reduced by folic acid supplementation before and during pregnancy. Epidemiological studies have shown low plasma folate and raised plasma homocysteine in women with spina bifida aperta (SB) children suggesting an abnormal folate metabolism. The 5,10-methylenetetrahydrofolate reductase (MTHFR) variant C677T, resulting in a decreased activity of the enzyme, has been associated with the development of NTD. Several studies demonstrated that homozygosity for the C677T mutation occurs at a higher frequency in patients with SB phenotype than in control individuals. The SB risk is strongest if both the mother and her child have the mutation in the homozygous state. In the present study we compared the frequency of the C- and T-alleles in healthy German individuals (n=153) with German SB patients (n=137). Our study groups reveal no significant difference in C/T-allele frequencies and genotype distributions. A family based association study, the transmission disequilibrium test, confirms the absence of an association between T-allele and SB. In 9 of 40 families we were able to exclude linkage to the MTHFR locus (1p36.3) employing different inheritance models. Conclusion Our data show no evidence for an association between the C677T mutation and the occurrence of the SB phenotype. Therefore we cannot support the hypothesis that the MTHFR variant does account for a significant genetic predisposition to the SB phenotype in the studied German patients. Received: 11 June 1997 / Accepted in revised form: 3 November 1997     

中草药来源的醛糖还原酶抑制剂的研究进展

中草药作为天然产物,无明显不良反应且来源广泛,以中草药为来源的醛糖还原酶抑制剂其不良反应远低于化学合成及微生物来源的醛糖还原酶抑制剂,在有效阻止和延缓糖尿病并发症如:糖尿病肾病、血管病变、视网膜病变、外周神经病变方面显示了良好的应用前景。作者主要综述了中草药活性成分黄酮类化合物及其衍生物,如:槲皮素、水飞蓟素、葛根素、黄芩苷、黄连素等和一些中药复方制剂,如:参丹健胰丸、筋脉通、六味地黄丸等在抑制醛糖还原酶的活性、降低山梨醇含量等方面取得的研究进展,并对其在治疗糖尿病并发症方面的现状进行了阐述。     

实时荧光定量PCR法检测MTHFR C677T基因多态性方法的建立和应用

目的:建立一种准确、快速、自动化程度较高的检测亚甲基四氢叶酸还原酶(MTHFR)C677T基因多态性的方法,并观察中国北方健康人群中MTHFR C677T基因频率。方法:应用MGB探针的原理建立MTHFR C677T基因多态的检测方法,与传统PCR-RFLP方法作对照,共检测标本88例,并计算各基因型频率。结果:荧光定量方法可以快速完成MTHFR C677T基因多态性的检测,检测结果得到传统PCR-RFLP方法的证实。88例北京汉族正常人群MTHFR基因的各种基因型频率为25％、42％和33％。结论:该方法准确、检测效率高,适用于临床实验室及流行病学调查研究。     

亚甲基四氢叶酸还原酶基因多态性与甘肃汉族2型糖尿病肾病的关系

目的 研究亚甲基四氢叶酸还原酶(MTHFR)基因多态性与汉族2型糖尿病肾病的关系。方法 应用聚合酶链反应—限制性片段长度多态性的方法，检测甘肃汉族人2型糖尿病患者91例，其中单纯糖尿病组50例，糖尿病肾病组41例，正常对照组35例，比较各组间MTHFR等位基因和基因型频率。结果 纯合基因型TT和杂合基因型CT在糖尿病肾病组的频率为34．1％和51．2％，高于糖尿病组(16％和48％)和正常对照组(14.3％和25．7％)，糖尿病肾病组的等位基因T频率(59．8％)也高于糖尿病组(40％)和正常对照组(27．1％)，差异均有统计学意义，糖尿病组和正常对照组之间的分布无统计学差异。结论 MTHFR基因C677T变异与甘肃汉族2型糖尿病患者糖尿病肾病的发病有关，等位基因T可能是糖尿病肾病的易感基因。     

原发性高血压肾损害及肾实质性高血压患者MTHFR基因多态性分析

目的探讨亚甲基四氢叶酸还原酶(MTHFR)基因C677T多态性与原发性高血压(EH)肾脏损害及肾实质性高血压(RH)的关系。方法用聚合酶链式反应限制性片段长度多态性(PCR-RFLP)分析法检测MTHFR基因多态性在正常人群(CN)、EH肾功能正常(EH-RN)患者、EH肾衰竭(EH-RF)患者及RH患者中的频率分布情况。结果EH-RF组和RH组的收缩压和舒张压水平均显著高于EH-RN组(P<0.05),各组间年龄、性别、血脂水平比较差异均无统计学意义(P>0.05)。EH-RF组MTHFR T等位基因频率为42.1%,明显高于正常对照(NC)组的18.3%和EH-RN组的19.2%(均P<0.05),其余各组间比较差异均无统计学意义(P>0.05)。各组之间MTHFR C/C、C/T和T/T基因型频率比较差异均无统计学意义(P>0.05)。结论MTHFR T等位基因可能是中国北方汉族EH患者发生肾衰竭的一个易感基因。     

原因不明复发性流产遗传性血凝因素研究

目的研究凝血因子V基因G1691A、凝血酶原基因G20210A以及5,10-亚甲基四氢叶酸还原酶(MTHFR)基因C677T和A1298C位点突变,与原因不明复发性流产易感相关性。方法采用聚合酶链式反应-限制性片断长度多态性分析方法,检测148例原因不明复发性流产者和82例正常对照的凝血因子V基因G1691A、凝血酶原G20210A以及MTHFR基因C677T和A1298C位点突变情况。结果复发性流产组和对照组,均未发现凝血因子V基因G1691A和凝血酶原基因G20210A突变;MTHFR基因C667T三种基因型在两组的总体分布存在显著性差异(P=0.012),其中复发性流产组CC基因型表达频率显著降低(P=0.005),T等位基因表达频率显著增大(P=0.004);MTHFR基因A1298C三种基因型在复发性流产和对照组总体分布无显著差异,AA/AC/CC基因型和A/C等位基因频率表达无统计学差异;MTHFR基因C677T/A1298C连锁分析发现8种连锁基因型,复发性流产组中677CC/1298AA表达频率显著降低(P<0.05),而677(CT TT)/1298CC仅在复发性流产组中表达(P<0.05)。结论中国人群复发性流产与凝血因子V基因G1691A和凝血酶原G20210A基因突变无关,而与MTHFR基因C677T和A1298C位点突变有关。     

蛋氨酸合成酶还原酶基因A66G多态性与Down综合征发生的相关研究

目的:研究蛋氨酸合成酶还原酶(MTRR)基因A66G多态性与Down综合征的关系。方法:采用聚合酶链反应-限制性片段长度多态性(PCR-RFLP)法对32例DS患儿母亲及70例未生育DS患儿女性MTRR的A66G进行基因分析。比较上述各组基因型和等位基因频率分布有无差异。结果:MTRR基因A66G突变型等位基因G频率在实验组和对照组中有显著性差异,GG基因型频率分布差异有显著性(P<0·05)。AG基因型比AA基因型生育DS患儿风险高1·98倍,GG基因型比AA基因型生育DS患儿风险高5·2倍。结论:MTRR A66G基因多态性与Down综合征发生相关,AG、GG基因型增加了Down综合征的发生风险。     

醛糖还原酶基因多态性同2型糖尿病肾病的相关性

目的：研究醛糖还原酶(AR)基因启动子区C(-12)G多态性同2型糖尿病肾病(DN)发生及发展的相关性。方法：采用PCR-RFLP技术在209例2型糖尿病和84例对照组人群中筛查该位点等位基因及基因型的频率，比较在无肾病组及肾病各组中频率的差异，以推断AR基因是否参与了肾病的发生和进展。结果：G等位基因在肾病组的分布频率是87．2％，高于无肾病组的78．1％和正常对照组的77．4％；GG基因型在肾病组的分布频率是74．4％，高于无肾病组的63．8％和正常对照组的57．1％。结论：AR基因-12位点G等位基因及GG基因型是2型DN发生的独立危险因素。     

一种人神经母细胞瘤辅酶II-依赖性视黄醇脱氢酶cDNA的克隆及特征分析

背景与目的:检测神经母细胞瘤中新的辅酶II_依赖性视黄醇脱氢/还原酶[NADP(H)_dependen tretinold ehydrogenase/reductase,NRDR]选择性剪接亚型。材料与方法:我们用NRDR特异引物,从人神经母细胞瘤细胞系SK_N_SH和SK_SY_5YcDNA中分别经PCR扩增出635bp和429bpDNA片段,测序证实635bp片段是NRDR,而429bp片段是选择性剪接新亚型。再用快速cDNA末端扩增(Rapidamplification of cDN Aends,RACE)方法得到429bp片段cDNA全长序列。用绿色荧光蛋白与新亚型的融合蛋白做亚细胞定位。结果:得到新亚型全长并命名为humanNRDRA2(hum NRDRA2)(AY616182)。已知NRDR有8个外显子,而新亚型hum NRDRA2由选择性剪接造成了第4和第6外显子丢失,从第5外显子开始读码框架前移1bp,导致随后的编码区框码漂移(frameshift),同时蛋白翻译终止信号提前出现,产生仅有188个氨基酸的蛋白,其中第137氨基酸以后的序列相对于NRDR完全发生改变,同时C_末端的过氧化物酶体定位信号_SRL丢失,却在160～176氨基酸处出现了一个细胞核定位信号。我们在ESTs库中未找到与其相同的剪接形式,提示它可能是神经母细胞瘤特有的一种NRDR剪接亚型。用GFP_NRDRA2融合蛋白做该蛋白的亚细胞定位,发现发绿色荧光的细胞均已悬浮,但悬浮状态不佳,而作为对照的NRDR另一亚型则能定位成功,提示NRDRA2蛋白可能具有一定的细胞毒性。结论:人神经母细胞瘤NRDRA2选择性剪接亚型羧基端框移突变并有核定位序列;该蛋白可能是一种细胞毒性蛋白。     

No evidence of association of methylenetetrahydrofolate reductase polymorphism with occurrence of second neoplasms after treatment of childhood leukemia

Methylenetetrahydrofolate reductase (MTHFR) polymorphisms have been associated not only with the risk for acute lymphoblastic leukemia (ALL) in adults and children, but also with increased methotrexate toxicity. The present study aimed to investigate whether MTHFR polymorphisms modify the risk for development of secondary malignancies in children treated for ALL with protocols that included high-dose methotrexate. MTHFR genotypes were determined in DNA samples isolated from archived bone marrow smears of 15 patients with a second malignancy and a matched control group of 30 patients who did not developed a second malignancy after the treatment for ALL. The frequencies of MTHFR C677T and A1298C genotypes in all patients were: C677T: CC 40%, CT 46.7% and TT 13.3% and A1298C: AA 46.7%, AC 44.4% and CC 8.9%. The relative risk for second malignancy was not significantly increased in ALL patients having at least one polymorphic C667T [odds ratio (OR) 1.51; 95% confidence interval (CI) 0.43 - 5.31] or one polymorphic A1298C allele (OR 1; 95% CI 0.29 - 3.46). Our study suggests that MTHFR polymorphisms are not associated with increased risk of second cancer in children treated with high-dose methotrexate.