Retinal expression of gamma-crystallins in the mouse

High levels of expression of a form of gamma-crystallin mRNA in mouse retina have been identified. Because the six murine gamma-crystallins have generally been regarded as specific to the lens, the expression of these crystallins at the mRNA and protein levels in the retina were evaluated in more detail.

Expression of gammaE/F-crystallin mRNA was examined by northern blot analysis and reverse transcription-polymerase chain reaction (RT-PCR) analysis applied to murine retinal and lens total RNAs. For gammaA-D-crystallin mRNAs, a multiplex RT-PCR was used on total cDNAs. The detection of total gamma-crystallin protein in the retina was performed using an antibody to bovine lens gamma-crystallins, applied to protein extracts in immunoblot analysis and to cryostat sections of ocular tissues in immunofluorescence studies.

By RT-PCR, we confirmed expression of both gammaE-and gammaF-crystallin as well as all four (gammaA-gammaD) remaining crystallins at the mRNA level in the mouse retina. Gamma-crystallin proteins were also detectable in murine retina by immunoblot analysis, although at a lower level than in the lens. By immunocytochemistry, gamma-crystallins were localized particularly to the inner retina, outer plexiform layer, and the photoreceptors during postnatal development.

Our findings of gamma-crystallin mRNA and protein expression in the retina indicate that none of the major crystallin classes is uniquely expressed in the lens. The expression of gamma-crystallins in the developing murine retina suggests a role analogous to the anti-stress properties established for the small heat-shock protein alphaB-crystallin, perhaps in response to varying exposure to light.