线粒体tRNA^(Leu(UUR))基因A3243G突变糖尿病家系的基因诊断

Gene diagnosis of a pedigree with the mitochondrial tRNA^(Leu)(UUR)A3243G mutation diabetes mellitus

目的确认一个由线粒体 tRNA^(Leu(UUR))基因 A3243G 点突变引起的母系遗传糖尿病家系,并分析其临床特征。方法采用 PCR 产物直接测序法对53例无血缘关系的有家族史的2型糖尿病(T2DM)患者线粒体 DNA(mitochondria DNA,mtDNA)片段(nt3153～nt3551)进行点突变筛选,然后对筛选到的 A3243G 异质性突变样本作 DHPLC 分析确认。详细调查此突变糖尿病家系发病特征,并做线粒体基因组全序列分析。结果在53例样本中检测到1例 A3243G 突变,对其家系调查发现7例母系成员中5例患病(1男4女),患者多数伴听力损害,体重指数减低,口服降糖药效果不佳最终需用胰岛素治疗,呈母系遗传,发病年龄不等,平均32.75岁。线粒体全基因组测序表明患者存在包括 A3243G 突变的共33个变异位点,但除 A3243G 突变外其余都不是进化上高度保守的位点,因此 A3243G 突变是与这个糖尿病家系发病有关的惟一的 mtDNA 突变。结论线粒体 tRNA^(Leu(UUR))基因 A3243G 突变是这个三代母系遗传糖尿病家系发病的原因,其临床特点是发病年龄轻、不胖、母系遗传、耳聋发生率和使用胰岛素比率高等。

Objective To identify maternally transmitted diabetes mellitus associated with the mitochondria DNA （mtDNA） tRNA^Leu （UUR） A3243G mutation and to investigate clinical characteristics in a three-generation Han Chinese family. Methods Direct sequencing of PCR product was applied to study the variations of mtDNA fragments （nt3153 -nt3551 ）in 53 unrelated T2DM patients with family history. The A3243G heterogeneous mutation was confirmed with DHPLC. Members of this pedigree were interviewed at length to identify clinical characteristics. The entire mitochondrial genome was analyzed. Results One subject with A3243G mutation was detected. Five （one males/four females） of seven matrilineal relatives in this family exhibited diabetes. The diabetes of these patients in frequently accompanied by hearing impairment, less Body Mass Index （BMI）, insulin therapy due to failure to oral hypoglycemic agents. The age of onset varies, with an average of 32. 75 years. Sequence analysis of the complete mitochondrial genome in this pedigree revealed the presence of the A3243G mutation and 32 other variants. However, none of other mtDNA variants are evolutionarily conserved and implicated to have significantly functional consequence. Thus, the A3243G mutation is the sole pathogenic mtDNA mutation associated with diabetes in this Chinese family. Conclusions The mutation at nucleotide 3243 in the mtDNA tRNA^Leu（UUR） gene is the cause of diabetes in the studied pedigree. The clinical characteristics associated with this mutation are young at onset, non obese, maternally inherited, and high prevalence of deafness and use of insulin.