A X-linked nonsense APOO/MIC26 variant causes a lethal mitochondrial disease with progeria-like phenotypes

Area of Science:

• Mitochondrial biology
• Genetics
• Human disease

Background:

• The MICOS complex, including APOO/MIC26, is crucial for mitochondrial structure and function.
• Mitochondrial dysfunction is implicated in various severe human diseases.

Purpose of the Study:

• To investigate the genetic basis and phenotypic consequences of a novel APOO/MIC26 variant.
• To elucidate the impact of this mutation on mitochondrial morphology and function.

Main Methods:

• Whole exome sequencing to identify gene mutations.
• Cellular studies to assess protein stability, localization, and mitochondrial morphology in patient-derived cells or models.

Main Results:

• Identified a nonsense mutation (c.532G>T) in APOO/MIC26 causing loss of 20 C-terminal amino acids.
• The mutation leads to an unstable MIC26 protein, but remaining protein localizes to mitochondria and interacts with MICOS subunits.
• Mutant MIC26 expression in knockout cells results in perturbed mitochondrial cristae architecture and fragmentation.

Conclusions:

• The identified APOO/MIC26 mutation is a loss-of-function variant.
• This mutation impairs mitochondrial morphology and cristae morphogenesis, causing a severe mitochondrial disease with progeria-like phenotypes.
• The findings highlight the critical role of MIC26 in maintaining mitochondrial integrity.