In contrast to our SOXD mouse model, SQORD and EE mice (41, 54) showed milder disease progression with average lifespan of weeks to months at comparable levels of H2S. Sqor–/– mice were indistinguishable from WT littermates before weaning, but later developed ataxia resulting in premature death at the age of 10 weeks. This evidence concerns the gene SQOR and sulfide quinone oxidoreductase deficiency.