原发性红斑性肢痛症致病基因的定位及突变研究

Gene Mapping and Mutation Identification in Patients with Primary Erythromelalgia

目的对原发性红斑性肢痛症的致病基因进行定位及突变研究。方法收集一个原发性红斑性肢痛症家系成员和一个散发病例的血样抽提基因组DNA,选用2号染色体长臂上已知致病区域的6个微卫星标记对该家系成员进行基因扫描,并对基因分型结果进行连锁分析及单倍型分析。PCR扩增SCN9A基因的全部外显子,并进行测序。针对所发现的突变以HphⅠ、BsrSⅠ内切酶行限制性片段长度多态性(RFLP)分析。结果连锁分析结果发现本家系在微卫星标记D2S2370和D2S2330的两点最大LOD值为2.11(重组率=0.00),单倍型分析发现本家系在微卫星标记D2S1353和D2S2345存在重组。家系患者和散发病例均存在SCN9A基因第15外显子的错义杂合点突变家系全部患者均存在T2573A杂合突变,散发病例存在T2543C杂合突变,分别导致Nav1.7第858位的亮氨酸被替换为组氨酸(L858H)及第848位的异亮氨酸被苏氨酸替换(I848T)。RFLP证实了正常对照无此突变。结论在世界上首次证明SCN9A基因是原发性红斑性肢痛症的候选致病基因。

Objective To map the specific gene responsible for primary erythromelalgia and identify gene mutations in a Chinese family and one sporadic patient with primary erythromelalgia. Methods Geno-mic DNA was extracted from peripheral lymphocytes of the family members of the pedigree and the sporadic patient. Scanning the genes on chromosome 2q that had been identified was performed by using 6 microsatellite markers for the family members with primary erythromelalgia. Then linkage analysis and haplotype analysis were conducted. All exons of SCN9A gene were analyzed by PCR-DNA sequencing. The mutation identification was also confirmed by restriction fragment length polymorphism(RFLP). Results A maximum 2-point LOD score of 2.11 was found at a recombination fraction (θ = 0.00) with markers D2S2370 and D2S2330. Recombination events were detected by markers D2S1353 and D2S2345 in this family by the haplotype analysis. There were two missense heterozygous point mutations in the 15th exon of SCN9A gene both in the family(T2573A) and the sporadic patient(T2543C), leading to the substitution of the amino acid leucine to histidine(L858H) and isoleucine to threonine(I848T), respectively. The above mutations were not found in 400 normal alleles. Conclusion It is proved that primary erythromelalgia is caused by mutations in SCN9A gene.