Corrigendum: Long-term survival in a child with severe encephalopathy, multiple respiratory chain deficiency and GFM1 mutations

Clinical and molecular findings in a family expressing a novel heterozygous variant of the G elongation factor mitochondrial 1 gene

The identified mutations in the G elongation factor mitochondrial 1 (GFM1) gene have been associated with heterogeneous clinical features of an early-onset mitochondrial disease in only 25 families. The present study reports the case of two siblings with a novel GFM1 variant and their clinical and laboratory presentations, which included progressive hepatic encephalopathy, failure to thrive and persistent lactic acidemia. Both histological changes and diminished expression of the GFM1 protein were observed in the liver and kidney tissues of the index patient. Whole-exome and Sanger sequencing technologies were used to diagnose the index patient with defective GFM1 using amniocentesis at 32 weeks' gestation. Heterozygous mutations in the GFM1 gene were identified in both siblings: A novel mutation, C1576T in exon 13 inherited from their asymptomatic mother, resulting in a premature stop codon at amino acid position 526 and the previously reported G688A mutation on the boundary between exon 5 and intron 5-6, inherited from their asymptomatic father. In conclusion, the present study reports two siblings carrying a novel GFM1 variant with a rare fatal mitochondrial disease.

Novel GFM2 variants associated with early-onset neurological presentations of mitochondrial disease and impaired expression of OXPHOS subunits

Mitochondrial diseases are characterised by clinical, molecular and functional heterogeneity, reflecting their bi-genomic control. The nuclear gene GFM2 encodes mtEFG2, a protein with an essential role during the termination stage of mitochondrial translation. We present here two unrelated patients harbouring different and previously unreported compound heterozygous (c.569G>A, p.(Arg190Gln); c.636delA, p.(Glu213Argfs*3)) and homozygous (c.275A>C, p.(Tyr92Ser)) recessive variants in GFM2 identified by whole exome sequencing (WES) together with histochemical and biochemical findings to support the diagnoses of pathological GFM2 variants in each case. Both patients presented similarly in early childhood with global developmental delay, raised CSF lactate and abnormalities on cranial MRI. Sanger sequencing of familial samples confirmed the segregation of bi-allelic GFM2 variants with disease, while investigations into steady-state mitochondrial protein levels revealed respiratory chain subunit defects and loss of mtEFG2 protein in muscle. These data demonstrate the effects of defective mtEFG2 function, caused by previously unreported variants, confirming pathogenicity and expanding the clinical phenotypes associated with GFM2 variants.