ACSL1 is an isozyme of the long-chain fatty-acid-coenzyme A ligase family. Although differing in substrate specificity, subcellular localization, and tissue distribution, all isozymes of this family convert free long-chain fatty acids into fatty acyl-CoA esters, and thereby play a key role in lipid biosynthesis and fatty acid degradation. ACSL1 is known to be involved in fatty-acid metabolism critical for heart function [10] and nonspecific mental retardation. Since the ACSL4 gene is highly expressed in brain, where it encodes a brain specific isoform, an ASCL1 mutation may be an efficient diagnostic tool in mentally retarded males.