Fig. 4.—

Elaboration of the metabolic and signaling oxysterols cascades in chordate evolution. Top—Binding specificities of LXRs to oxysterols in cephalochordates, tunicates, cyclostomes and chondrichthyans: red and blue boxes represent no activation and activation of LXR-dependent transcription, respectively, and light blue boxes represent residual LXR activation. Bottom—Schematic representation of cholesterol synthesis and oxidation pathways: green ✓ and red X stand for presence or absence of the corresponding cytochrome P450s oxygenase (CYP) gene, respectively (Nelson et al. 2013).