Mutations in MTHFR and POLG impaired activity of the mitochondrial respiratory chain in 46-year-old twins with spastic paraparesis

• Published in: Journal of human genetics 2020-01, Vol.65 (2), p.91-98
• Main Authors: Wiedemann, Arnaud, Chery, Céline, Coelho, David, Flayac, Justine, Gueguen, Naïg, Desquiret-Dumas, Valérie, Feillet, François, Lavigne, Christian, Neau, Jean-Philippe, Fowler, Brian, Baumgartner, Matthias R, Reynier, Pascal, Guéant, Jean-Louis, Oussalah, Abderrahim
• Format: Article
• Language: English
• Subjects: Defects; DNA Polymerase gamma - genetics; Electron transport; Female; Fibroblasts; Genes; Genetics; Genomes; Genomics; Genotype & phenotype; Hereditary spastic paraplegia; Heterozygote; High-Throughput Nucleotide Sequencing; Homocysteine; Hospitals; Humans; Hyperhomocysteinemia; Inborn errors of metabolism; Metabolism; Methylenetetrahydrofolate reductase; Methylenetetrahydrofolate Reductase (NADPH2) - genetics; Middle Aged; Mitochondria; Mitochondrial Diseases - diagnosis; Mitochondrial Diseases - genetics; Mitochondrial DNA; Mutation; Next-generation sequencing; Ontology; Paralysis; Paraparesis, Spastic - diagnosis; Paraparesis, Spastic - genetics; Phenotypes; Sequence Analysis, DNA; Spastic paraparesis; Spastic Paraplegia, Hereditary - diagnosis; Spastic Paraplegia, Hereditary - genetics; Spasticity; Twins, Monozygotic
• ISSN: 1434-5161; 1435-232X
• DOI: 10.1038/s10038-019-0689-y

Hereditary spastic paraplegias (HSPs) are characterized by lower extremity spasticity and weakness. HSP is often caused by mutations in SPG genes, but it may also be produced by inborn errors of metabolism. We performed next-generation sequencing of 4813 genes in one adult twin pair with HSP and severe muscular weakness occurring at the same age. We found two pathogenic compound heterozygous variants in MTHFR, including a variant not referenced in international databases, c.197C>T (p.Pro66Leu) and a known variant, c.470G>A (p.Arg157Gln), and two heterozygous pathogenic variants in POLG, c.1760C>T (p.Pro587Leu) and c.752C>T (p.Thr251Ile). MTHFR and POLG mutations were consistent with the severe muscle weakness and the metabolic changes, including hyperhomocysteinemia and decreased activity of both N(5,10)methylenetetrahydrofolate reductase (MTHFR) and complexes I and II of the mitochondrial respiratory chain. These data suggest the potential role of MTHFR and POLG mutations through consequences on mitochondrial dysfunction in the occurrence of spastic paraparesis phenotype with combined metabolic, muscular, and neurological components.