CYP27A1 and amyotrophic lateral sclerosis: High plasma levels of cholesterol have been suggested to be neuroprotective for ALS and to be associated with an increased survival time (9–11), but other data suggest that accumulation of cholesterol esters and ceramides mediate oxidative stress in motor neurons in ALS (12), while the gene cytochrome P450 27A1 (CYP27A1), encoding cholesterol (25R)26-hydroxylase (also known as sterol 27-hydroxylase), the first enzyme in the extrahepatic part of the bile acid biosynthesis pathway, was recently identified as a susceptibility gene for sporadic ALS (13).