Purpose: To evaluate the expression of betaB(2)-crystallin mRNA and protein in rat, bovine, and human nonlens and nonocular tissues.
Methods: betaB(2)-crystallin mRNA levels were detected by RT-PCR. betaB(2)-crystallin protein was purified from rat and bovine tissues by FPLC chromatography. FPLC fractions were analyzed by immunoblotting. The identity of betaB(2)-crystallin protein, isolated from the retina, was confirmed by protein microsequencing.
Results: betaB(2)-crystallin transcript was detected in rat brain, rat testis, and human retina by RT-PCR. betaB(2)-crystallin transcript was not found in rat lung, heart, ovary, spleen, thymus, kidney, and liver or in human brain and testis. betaB(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 betaB(2)-crystallin by protein microsequencing.
Conclusions: These results establish that betaB(2)-crystallin mRNA and protein are expressed in tissues outside of the lens and outside of the eye including retina, brain, and testis. Extralenticular and extraocular expression of betaB(2)-crystallin, coupled with its participation in phosphorylation pathways, suggests that it has nonrefractive functions in these tissues.