The enzyme responsible, CYP46A1, is predominantly expressed in the brain [312] – most highly in areas affected by AD [359] – and polymorphisms in the gene cytochrome P450, family 46, subfamily A, polypeptide 1, CYP46A1 (14q32.1), have been associated with risk of AD development (e.g. [360]). Here, CYP46A1 is linked to Alzheimer disease.