The protein encoded by this gene is a histone lysine demethylase that preferentially acts on histones in the monomethyl or dimethyl states. The encoded protein requires Fe(2+) ion, 2-oxoglutarate, and oxygen for its catalytic activity. Defects in this gene are a cause of mental retardation syndromic X-linked Siderius type (MRXSSD). Four transcript variants encoding different isoforms have been found for this gene. [provided by RefSeq, May 2010].