ELOVL2 is the sole elongase that elongates C22–C24 PUFA in liver. PUFA composition of phospholipid pool (A) and TG pool (B) from liver, as well as total fatty acid composition of serum (C) in wild-type and Elovl2−/− animals fed standard chow diet. For the % mole composition of the remaining fatty acids, see supplementary Tables III, IV, and V, respectively. Biosynthesis of PUFAs in the liver (D) where ELOVL2 specifically elongates 22:5n-3 and 22:4n-6 fatty acids to form precursors (24:5n-3 and 24:4n-6) for DHA and DPAn-6 formation. Results shown are means ± SEM of 3–6 mice. Statistical significances are shown between wild-type and Elovl2−/− mice (* P < 0.05, ** P < 0.01, *** P < 0.001, and **** P < 0.0001).