Oxysterol 7alpha-hydroxylase that mediates formation of 7-alpha,25-dihydroxycholesterol (7-alpha,25-OHC) from 25-hydroxycholesterol. Plays a key role in cell positioning and movement in lymphoid tissues: 7-alpha,25-dihydroxycholesterol (7-alpha,25-OHC) acts as a ligand for the G protein-coupled receptor GPR183/EBI2, a chemotactic receptor for a number of lymphoid cells. 25-hydroxycholesterol + O2 + reduced [NADPH--hemoprotein reductase] = 7alpha,25-dihydroxycholesterol + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] (25R)-cholest-5-ene-3beta,26-diol + O2 + reduced [NADPH--hemoprotein reductase] = (25R)-cholest-5-en-3beta,7alpha,26-triol + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] Lipid metabolism; bile acid biosynthesis. Highly expressed in brain; also expressed in liver and kidney. Belongs to the cytochrome P450 family.