FMR1 and fragile X syndrome: A study on fibroblasts derived from unaffected control males, FXS patients, individuals with premutation (PM), and unmethylated full mutation (FM) revealed that decreased FMRP expression might be responsible for altered mitochondrial morphology (“donut-shaped mitochondrial morphology”), upregulation of mitochondrial oxidative phosphorylation complexes and other proteins, and increased cellular sensitivity to apoptotic stimuli [84].