LSD1 or KDM1A (lysine (K)-specific demethylase 1A) gene encodes a nuclear protein which contains a SWIRM domain, a FAD-binding motif, and an amine oxidase domain. This protein is a component of several histone deacetylase complexes. LSD1 or KDM1A is a demethylase that acts on both Lys 4 and 9 of histone H3. Consequently depending upon the use it may act as a co-activator or a co-repressor. It may have a role in the repression of neuronal genes. Two isoforms of LSD1 have been reported which are produced by alternative splicing. LSD1 has more or less ubiquitous expression.