Cholesterol and fatty acids are essential, abundant components of neuronal tissue. Acetoacetyl-CoA synthetase (AACS) is a ketone body-utilizing enzyme for the synthesis of cholesterol and fatty acids and is highly expressed in the brain. In this study, we investigated the regulation of AACS during neurite outgrowth to clarify the physiological role of AACS in neurogenesis. Messenger RNA levels and the expression of AACS were increased during neurite outgrowth in Neuro-2a cells. The expression of HMG-CoA reductase, a key enzyme of cholesterol biosynthesis, was also increased. ChIP assays showed that the amount of SREBP-2, a key transcription factor of cholesterol synthesis, interacted with the AACS promoter was increased during neurite outgrowth, and knockdown of SREBP-2 down-regulated the mRNA levels of AACS in Neuro-2a cells. The expression of AACS in the brains of mouse embryos was dramatically increased between E16.5 and E18.5. Moreover, knockdown of AACS in primary neurons caused decreases in the expression of MAP-2 and NeuN, which are markers of neuronal differentiation, as well as synaptopodin, a marker of spine apparatus. These results suggest that AACS is regulated by SREBP-2 and involves in the normal development of neurons. (C) 2012 Elsevier Inc. All rights reserved.