RBP4 and cone dystrophy: Zebrafish with a mutant RBPR2 containing a defective RBP4 binding domain (rbpr2fs−muz99); thereby disrupting the proper docking of RBP4 bound retinol to the transporter, causes rod and cone dystrophy, decreased ocular retinoid content, and a significant decrease in expression of enzymes involved in the processing and regulation of retinoids [42].