Expression of beta B-2-crystallin mRNA and protein in retina, brain, and testis

PURPOSE. To evaluate the expression of beta B-2-crystallin mRNA and protein in rat, bovine, and human nonlens and nonocular tissues. METHODS. beta B-2-crystallin mRNA levels were detected by RT-PCR. beta B-2- crystallin protein was purified from rat and bovine tissues by FPLC chromat ography. FPLC fractions were analyzed by immunoblotting. The identity of be ta B-2-crystallin protein, isolated from the retina, was confirmed by prote in microsequencing. RESULTS. beta B-2-crystallin transcript: was detected in rat brain, rat tes tis, and human retina by RT-PCR. beta B-2-crystallin transcript was not fou nd in rat lung, heart, ovary, spleen, thymus, kidney, and liver or in human brain and testis. beta B-2-crystallin protein was partially purified from and its identity confirmed in rat brain. rat testis, and bovine retina. The bovine retinal protein was further confirmed to be authentic beta B-2-crys tallin by protein microsequencing. CONCLUSIONS. These results establish that beta B-2-crystallin mRNA and prot ein are expressed in tissues outside of the lens and outside of the eye inc luding retina, brain, and testis. Extralenticular and extraocular expressio n of beta B-2-crystallin, coupled with its participation in phosphorylation pathways, suggests that it has nonrefractive functions in these tissues.