Abundant FUS-immunoreactive pathology in the skin of sporadic amyotrophic lateral sclerosis

The fused in sarcoma (FUS) protein is a 526 amino acid and its expression is ubiquitous. Recently, mutations in a gene coding FUS have been identified in familial amyotrophic lateral sclerosis (ALS). Also, FUS has been found in neuronal cytoplasmic inclusions in sporadic forms of ALS, suggesting that FUS has an important role in the neurodegeneration occurring in sporadic disease. However, there has been no study of FUS in ALS skin.We made a quantitative immunohistochemical study of the expression of FUS in the skin from patients with sporadic ALS and controls.The proportion of FUS-immunoreactive (ir) cells in the epidermis in ALS patients was significantly higher (P < 0.001) than in controls. There was a significant positive relationship (r = 0.78, P < 0.001) between the proportion and duration of illness in ALS patients. The optical density of FUS-ir cells in the epidermis in ALS patients is markedly stronger (P < 0.001) than in controls. There was a significant positive relation (r = 0.49, P < 0.05) between the immunoreactivity and duration of illness in ALS patients.These data suggest that changes of FUS in ALS skin are related to the disease process, and that metabolic alterations of FUS may take place in the skin of patients with ALS.