Mice lacking the mitochondrial exonuclease MGME1 develop inflammatory kidney disease with glomerular dysfunction.

Area of Science:

• Mitochondrial biology
• Genetics
• Pathophysiology

Background:

• Mitochondrial DNA (mtDNA) maintenance disorders arise from nuclear gene mutations, causing varied syndromes.
• Loss-of-function mutations in MGME1 lead to mtDNA deletions/depletion, resulting in adult-onset multisystem mitochondrial disease.

Purpose of the Study:

• To investigate the in vivo function of MGME1.
• To characterize the pathophysiology of MGME1-associated mitochondrial disease using a knockout mouse model.

Main Methods:

• Extensive phenotyping of aging Mgme1 knockout mice.
• Analysis of de novo formation and degradation of linear deleted mtDNA fragments.
• Assessment of age-related phenotypes including weight, vision, and kidney function.

Main Results:

• Loss of MGME1 causes de novo formation and degradation of linear deleted mtDNA fragments.
• MGME1 is critical for completing mtDNA replication, not degrading linear fragments.
• Mgme1 knockout mice exhibit progressive weight loss, cataracts, retinopathy, and severe chronic progressive nephropathy with kidney inflammation.

Conclusions:

• Defective mtDNA replication due to MGME1 deficiency triggers an immune response.
• This immune response contributes to age-associated kidney pathology, linking faulty mtDNA synthesis to inflammatory disease.