Similar to the loss of a4 function, mutations in the ATP6V0A2 locus, which encodes the a2 subunit, do not seem to cause visual impairment, whereas the loss of the a2 subunit results in an abnormal assembly of the extracellular matrix and skin (cutis laxa), probably because of defective posttranslational glycosylation [35]. This evidence concerns the gene ATP6V0A2 and cutis laxa.