Heteroplasmy level of the mitochondrial tRNaLeu(UUR) A3243G mutation in a Chinese family is positively associated with earlier age-of-onset and increasing severity of diabetes.
OBJECTIVE
To investigate the mutations of mitochondrial genome in a pedigree with suspected maternally inherited diabetes and deafness and to explore the correlations between the mutations and clinical features.


METHODS
Genomic DNA was isolated from blood leucocytes of each member of the pedigree. The mitochondrial genome was amplified with 24-pair primers that could cover the entire mitochondrial DNA. Direct sequencing of PCR products was used to identify any mitochondrial DNA mutations.


RESULTS
Family members on the maternal side all harbored the tRNALeu(UUR) A3243G mutation. The paternal side family members did not have the mutation. The age-of-onset of diabetes of the 4 maternal side family members was 15, 41, 44, and 65 years old, and their corresponding heteroplasmy level of the mutation was 34.5%, 14.9%, 14.6%, and 5.9%, respectively. The age-of-onset of diabetes and heteroplasmy level of A3243G mutation were negatively correlated with a correlation coefficient of -0.980 (P = 0.02). Meanwhile, patient with high heteroplasmy level of A3243G mutation had relatively low severity of disease. Moreover, 6 reported polymorphisms and 2 new variants were found.


CONCLUSIONS
The main cause of diabetes in this pedigree is the tRNALeu(UUR) A3243G mutation. However, other gene variants may contribute to its pathogenicity. The heteroplasmy level of the tRNALeu(UUR) A3243G mutation is positively associated with earlier age-of-onset and increasing severity of diabetes.
Zhang
Shi
S
Department of Endocrinology, Key Laboratory of Endocrinology of Ministry of Health, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China.
Tong
An-li
AL
Zhang
Yun
Y
Nie
Min
M
Li
Yu-xiu
YX
Wang
Heng
H
D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D000368:Aged; D044466:Asian People / Q000235:genetics*; D002681:China; D003922:Diabetes Mellitus, Type 1 / Q000175:diagnosis* / Q000235:genetics*; D005260:Female; D034381:Hearing Loss / Q000235:genetics; D006801:Humans; D008875:Middle Aged; D008928:Mitochondria / Q000235:genetics*; D010375:Pedigree; D017354:Point Mutation / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D012343:RNA, Transfer / Q000235:genetics; D012356:RNA, Transfer, Leu / Q000235:genetics*; D055815:Young Adult
D012356:RNA, Transfer, Leu; D012343:RNA, Transfer