ABCG8 and sitosterolemia: They rather result in disease due to classical point mutations (e.g., mutations in CYP1B1 result in glaucoma [26], mutations in ABCG8 are associated with sitosterolemia [30]), or knockout animals have been shown to develop a phenotype (i.e., Otx1 knockout mice show epileptic behavior [31], Vax2 knockout results in abnormal retinal and optic nerve development [32], and Zfp36l2 knockout is embryonically lethal [33]).