Histone demethylase that specifically demethylates both mono- and dimethylated 'Lys-9' of histone H3. May act as a transcription regulator controlling hair biology (via targeting of collagens), neural activity, and cell cycle. 2 2-oxoglutarate + N(6),N(6)-dimethyl-L-lysyl(9)-[histone H3] + 2 O2 = 2 CO2 + 2 formaldehyde + L-lysyl(9)-[histone H3] + 2 succinate Binds 1 Fe(2+) ion per subunit. Expressed predominantly in brain, hair follicles and interfollicular epidermis. No expression in dermis. Contains two Leu-Xaa-Xaa-Leu-Leu (LXXLL) motifs. The LXXLL motifs are essential for the association with nuclear receptors (By similarity). The JmjC domain and the C6-type zinc-finger are required for the demethylation activity. Defects in Hr are the cause of a number of pleiotropic effects including structural abnormalities of epithelial cells in the hair follicles, hair loss towards the end of the first hair growth cycle, and the failure of subsequent hair growth cycles. Older mice carrying a hr mutation have been reported to possess altered ratios of T-cell-dependent B-cell responses. Mice homozygous for hr mutation are uniquely sensitive to UV and chemically induced skin tumors.