Histone demethylase required for nervous system development (PubMed:20346720). Specifically demethylates dimethylated 'Lys-9', 'Lys-23' and 'Lys-27' (H3K9me2, H3K23me2 and H3K27me2, respectively) of histone H3, thereby playing a central role in histone code (PubMed:20346720, PubMed:21251613, PubMed:20567262, PubMed:26476455). Promotes mitochondrial stress-induced longevity (PubMed:27133168). Binds 1 Fe(2+) ion per subunit. Competitively inhibited by 2-hydroxyglutarate. Mainly expressed in neurons. Also weakly expressed in some muscle, intestinal and hypodermal cells. The PHD-type zinc finger mediates binding to H3K4me3. Impaired locomotion (PubMed:20346720). While wild-type animals move by alternating dorsal and ventral flexions along the body length, producing a regular sinusoidal track on bacteria, the track pattern left by mutants is irregular, with increased wavelength (distance between successive peaks of a wave) but unchanged amplitude of the wave (PubMed:20346720). An increase of H3K9me2 and H3K27me2 levels is observed (PubMed:20346720). RNAi-mediated knockdown suppresses mitochondrial stress-mediated longevity (PubMed:27133168). Belongs to the JHDM1 histone demethylase family. JHDM1D subfamily.