Family Investigation And Genetic Mutation Study Of A Patient With Mitochondrial Diabetes

Object:To make a gene diagnosis for a patient with clinical manifestation of "diabetes mellitus, hearing impairment, optic atrophy, diabetes insipidus, and hyperlactacidemia" by investigating the WFS1mutation and mitochondrial mutation of the patient as well as the heteroplasmy level of the mitochondrial mutation of the patient and his pedigree.Method:(1) Collect related clinical data.(2) Draw the anticoagulant blood of the proband and some of his families, then extract DNA from the peripheral leucocytes of the blood.(3) PCR and direct sequencing were performed to screen for mutations mitochondrial DNA.(4) Construct the wild type plasmid and mutant plasmid, detect the heteroplasmy level of mitochondrial mutations of all of the mutation carriers by realtime PCR.Results:A base deletion was present in the exon3of the proband, causing a heterozygous frameshift mutation, which caused the premature stop of the translation of the WFS1and the abnormality of the sequences of amino acids of Wolframin. The father and younger sister were both mutation carriers, but genotype of the mother was normal. The mitochondrial3243A-G mutation was as detected in the proband and all of his maternal relatives but his younger sister and younger female cousin. There was a CCCCCTCTA deletion from8271-8280of the sequences of mitochondrial genome of the proband and his maternal relatives. Realtime PCR was used to detect the mutation of the proband and all his maternal relatives, the heteroplasmy level of the detected mutations were calculated then. The mitochondrial3243A-G mutation was detected in the proband’s younger sister and younger cousin this time, indicating that the mutation was transmitted maternally.Conclusion:(1)The gene diagnosis of the patient was mitochondrial diabetes. The pathogenic mutation was mitochondrial DNA3243A-G (2)The deletion of CCCCCTCTA in the mitochondrial genome may contribute to the pathogenesis of the patient.(3) The base deletion of the exon3of WFS1was not pathogenic.