[Molecular scanning of mtDNA gene in two early-onset diabetic pedigrees]

To search for new potential diabetogenic mtDNA defects by scanning mtDNA genome in mitochondrial DNA diabetes (MDM) pedigrees.

Blood samples were collected from the family members in two suspected MDM pedigrees, which were both maternal transmitted and early-onset diabetes. The whole mtDNA genome except D-loop was detected by direct sequencing in probands of these two diabetic pedigrees. Novel mutations displayed by direct sequencing were then screened in 200 normal glucose tolerant controls and 100 early-onset diabetic patients.

We found a novel nt14319T --> C mutation in No. 2 pedigree, but no pathogenic mutation was found in No. 1 pedigree. The mutation of nt14319T --> C, which not being reported previously, locate in the region of ND6 subunit, causing amino acid change (asparagine --> aspartic acid). The frequencies of 14319T/C substitution in 100 early-onset diabetic patients and 200 control subjects were 6% and 5%(P > 0.05).

A novel mutation 14319T --> C was identified in No. 2 pedigree. All three diabetic family members in this pedigree haboured 14319T --> C mutation, indicating that it may be the major pathogenic mutation for this family.