Homozygous YME1L1 mutation causes mitochondriopathy with optic atrophy and mitochondrial network fragmentation.

Mitochondriopathies often present clinically as multisystemic disorders of primarily high-energy consuming organs. Assembly， turnover， and surveillance of mitochondrial proteins are essential for mitochondrial function and a key task of AAA family members of metalloproteases. We identified a homozygous mutation in the nuclear encoded mitochondrial escape 1-like 1 gene YME1L1， member of the AAA protease family， as a cause of a novel mitochondriopathy in a consanguineous pedigree of Saudi Arabian descent. The homozygous missense mutation， located in a highly conserved region in the mitochondrial pre-sequence， inhibits cleavage of YME1L1 by the mitochondrial processing peptidase， which culminates in the rapid degradation of YME1L1 precursor protein. Impaired YME1L1 function causes a proliferation defect and mitochondrial network fragmentation due to abnormal processing of OPA1. Our results identify mutations in YME1L1 as a cause of a mitochondriopathy with optic nerve atrophy highlighting the importance of YME1L1 for mitochondrial functionality in humans.