MICOS13, also known as QIL1, MIC13, or C19orf70, is a component of the MICOS complex. This complex is crucial for maintaining cristae junctions at the mitochondrial inner membrane, which are implicated in regulating oxidative phosphorylation, apoptosis, and import of lipids and proteins [1,3,4].

In a patient with hepato-encephalopathy and mitochondrial DNA depletion syndrome (MTDPS), a novel homozygous frameshift variant, c.13_29del (p.Trp6Profs*71) in MICOS13 was identified. Loss of the MICOS13 protein led to fewer cristae structures in the patient's fibroblasts. Rescuing mitochondrial respiratory chain complex deficiencies by stable expression of wild-type MICOS13 cDNA in the patient's fibroblasts suggested that this novel variant causes hepato-encephalopathy with MTDPS [1]. In another study, exome sequencing of patients suspected of having mitochondrial diseases identified pathogenic variants in MICOS13 among other genes [2].

In summary, MICOS13 is essential for maintaining mitochondrial cristae junctions and normal mitochondrial function. Genetic variants in MICOS13 are associated with severe mitochondrial diseases, such as hepato-encephalopathy with MTDPS. Understanding the role of MICOS13 through patient-based functional studies helps to elucidate the molecular mechanisms underlying these mitochondrial disorders.