Altered mitochondrial function in fibroblast cell lines derived from disease carriers of spinal muscular atrophy.

ABSTRACT

BACKGROUND: Spinal muscular atrophy (SMA) is an autosomal recessive childhood-onset neuromuscular disease with a carrier frequency of ~150. Mitochondrial abnormalities are widespread in patients with SMA. Disease carriers for SMA (i.e., the parents of patients with SMA) are viewed as asymptomatic for SMA disease. As far as we are aware, mitochondria have not been previously examined in SMA carriers, yet as they are maternally inherited, mitochondrial function in SMA carriers has putative implications for disease pathogenesis. METHODS: Fibroblast cell lines derived from SMA carriers and controls were obtained from two different sources and cultured under standard conditions. The mitochondrial membrane potential, reactive oxygen species (ROS) production, citrate synthase activity, and bioenergetic analysis were examined as measures of mitochondrial function. The mitochondrial genome was also sequenced in a subset of the fibroblast cell lines to identify any mitochondrial DNA variants. RESULTS: Here, we show a depolarized mitochondrial membrane potential, increased levels of reactive oxygen species, and reduced citrate synthase activity in SMA carriers compared with controls. A likely pathogenic variant in the MT-CO3 gene (which encodes subunit III of cytochrome c oxidase) was also identified in a paternal carrier. CONCLUSIONS: This study was conducted as a preliminary investigation of mitochondrial function in SMA carriers. Our findings suggest that disease carriers of SMA show differences in mitochondrial function, indicative of a subclinical mitochondrial phenotype. Further investigation in a larger sample set is warranted.

Spinal muscular atrophy (SMA) is a disease that mostly affects children in which the muscles become weaker over time, and often leads to death in untreated individuals. It is caused by a defective gene that children often inherit from their parents. The parents of children with SMA are known as disease carriers if they do not show any symptoms of SMA themselves. We studied skin cells from the parents of people with SMA and found changes in a component of the cells called the mitochondria. These changes are not normally present in healthy individuals. Further work is needed to fully understand the implications of our findings for those with SMA and their parents.