βB2-crystallin in the mammalian retina

β-crystallins are abundant lens proteins in most, if not all vertebrate species. We have previously reported the presence of low levels of β-crystallins in chick non-lens tissues, both ocular and extra-ocular, including the expression of βB2-crystallin in the retina. Here we report that extralenticular β-crystallin expression is also found in mammals. βB2-crystallin is expressed in mouse and cat neural and pigmented retinas and in cat iris. Although present at levels lower than those found in the lens, the appearance and accumulation of βB2-crystallin in the neural retina coincides with the functional maturation of this tissue.