应用突变直接检测联合SNPs家系连锁分析进行眼皮肤白化病Ⅱ型的产前基因诊断

Prenatal genetic diagnosis of ocuiocutaneous albinism type H through mutation detection combined with SNPs linkage analysis

目的为仅检出1个致病等位基因的两个眼皮肤白化病（0culocutaneous albinism，OCA）的核心家系进行分型并提供产前基因诊断。方法应用DNA测序法检测先证者的TYR、P、TYRP1和SLC45A24个OCA基因，结合临床表型特点判定其OCA类型，在此基础上运用突变位点检测结合致病基因内单核苷酸多态位点家系连锁分析法进行产前基因诊断。结果家系1先证者仅在P基因检出c．1255c〉T杂合性致病突变，该突变来自母亲，结合临床表型特征综合分析判定先证者为OCA2患者。羊水筛查未见致病突变，家系连锁分析结果提示胎儿为0CA2携带者，出生时表型正常；家系2先证者仅在P基因检出c.1920_1949de130bp和ins AACA杂合性致病突变，该突变来自父亲，结合临床表型特征综合分析判定先证者为OCA2患者。羊水筛查检出c．1920_1949 de130bp和insAACA杂合突变，家系连锁分析结果提示胎儿为OCA2携带者，出生时表型正常。结论首次成功应用突变直接检测联合单核苷酸多态位点家系连锁分析法完成只检出1个致病突变的家系的OCA产前诊断。

Objective To provide prenatal diagnosis for two families affected with oculocutaneous albinism （OCA）, in both of which only 1 pathogenic allele has been identified. Methods To determine the clinical classification of OCA through DNA sequencing for TYR, P, TYRP1 and SLC45A2 genes in combination with phenotype analysis. Prenatal diagnosis was carried out by direct sequencing and intragenic SNPs family-based linkage analysis. Results In the first family, only 1 heterozygous mutation c. 1255C〉T was found in the proband, which was inherited from her mother. Together with its clinical phenotype, the proband was suspected to have OCA2. Screening of amniotic fluid, however, has found no mutation. With family-based linkage analysis, the fetus was deemed to be an OCA2 carrier. In the second family, again only one heterozygous mutation c. 1920_1949 del30bp and ins AACA was found in the proband, which was inherited from her father. Together with its clinical phenotype, the proband was suspected to have OCA2. Screening of amniotic fluid has revealed a heterozygous mutation c. 1920_1949 del30bp and ins AACA. By family-based linkage analysis, the fetus was deemed to be an OCA2 carrier. Both fetuses had a normal phenotype at birth. Conclusion Prenatal genetic diagnosis has been provided for the first time for two families affected with OCA, in which only 1 pathogenic mutant allele was detected. The combined mutation detection and SNPs linkage analysis has turned out to be successful.