Bestrophin-1 (BEST1) is a 68 kDa transmembrane protein which belongs to the bestrophin family of anion channels. It is predominantly expressed in the basolateral membrane of the retinal pigment epithelium. Studies show that bestrophin 1 functions as a Ca(2+)-dependent Cl(-) channel and modulator of voltage-dependent L-type Ca(2+) channels. It may also contribute to the basolateral cell conductance in airway epithelial cells. This protein is encoded by the VMD2 gene. Mutations in VMD2 can lead to different types of retinal or macular degenerations, including Best vitelliform macular dystrophy (BMD), autosomal recessive bestrophinopathy (ARB), autosomal dominant vitreoretinochoroidopathy (ADVIRC) and adult-onset vitelliform macular dystrophy (AVMD).