中文摘要：

目的：探讨配对盒基因（pair box 3，PAX3）突变对小眼球畸形相关转录因子（microphthalmia－asso‐ciated transcription factor ，MITF）基因转录活性的影响及其在I型Waardenburg综合征（Waardenburg syndrome ， WS）发病中的作用。方法野生型PAX3及其致病突变H80D和H186fsX5表达质粒瞬时转染293T细胞，应用荧光素酶活性检测系统对M IT F报告基因活性检测，观察野生／突变 PAX3蛋白对其靶基因M IT F转录活性的调控作用及二个突变蛋白对野生PAX3蛋白功能的影响；应用生物素标记的含序列attaat的DNA寡核苷酸链探针分别沉淀PAX3、H80D和H186fsX5蛋白，检测野生／突变PAX3蛋白与靶基因MITF启动子的结合力。结果尽管H80D蛋白仍残余部分功能可增加M IT F启动子转录活性，但与野生PAX3蛋白相比，二者差异有显著统计学意义（P＜0．01），而 H186fsX5蛋白则完全失去调控MITF启动子转录活性作用（P＜0．01）；二者均未对野生PAX3蛋白功能产生显性负效应作用（P＞0．05）。突变 H80D蛋白与野生 PAX3蛋白均可与MITF启动子特异DNA序列attaat结合，而突变H186fsX5蛋白则不能与之结合。结论 H80D和H186fsX5影响靶基因M IT F转录活性，使其表达下调、黑色素合成减少，以单倍体剂量不足效应致I型WS。

英文摘要：

Objective To investigate the impact of pair box 3 （PAX3） gene mutations on transcriptional ac‐tivity of target gene microphthalmia -associated transcription factor （MITF） and the role it plays in the pathogene‐sis of Waardenburg syndrome type I .Methods The 293T cells were transient transfected with wild type （WT ） PAX3 and mutant type （M T ） H80D ,H186fsX5 plasmids .We observed and analysed the regulation effects of WT/MT PAX3 on the transcriptional activities of MITF and the influence of the two mutants on WT PAX3 function u‐sing luciferase activity assays ,detect DNA binding capacity of WT/MT PAX3 to MITF gene promoter using a bioti‐nylated double - stranded oligonucleotide probe containing PAX3 binding motif ATTAAT to precipitate PAX3 , H80D and H186fsX5 respectively .Results H80D mutant was partially functional and was able to transactivate the MITF promoter in part ,but it was dramatically reduced as compared with WT PAX 3（P〈0 .01） .H186fsX5 mu‐tant was loss -of -function and failed to transactivate the MITF promoter as compared with WT PAX 3 （P〈0 .01） . None of them showed dominant -negative effect on WT PAX3（P〉0 .05） .WT PAX3 and H80D mutant were able to bind specifically to the ATTAAT motif on the MITF promoter ,whereas H186fsX5 PAX3 lost the DNA -binding ability .Conclusion The mutations H80D and H186fsX5 made down-regulation of MITF transcription and decrease syn‐thesis of melanin ,which resulted in haploinsufficiency of PAX3 protein and caused mild phenotypes of WS1 .