Differential expression of splice variants of chemokine CCL27 mRNA in lens, cornea, and retina of the normal mouse eye.

Purpose: Constitutive expression of RNA sequences complementary to the chemokine CCL27 mRNA has been found in the normal mouse eye. This study examines the nature and location of these endogenous RNAs in ocular tissues.

Methods: Conventional RT-PCR, 5' RACE, and dideoxy DNA sequencing were used to examine the sequences of CCL27 related RNAs in the eye. Expression levels of specific RNAs were measured by real time PCR. Tissue distribution of RNA transcripts was determined by RT-PCR using RNA from microdissected tissues and by in situ hybridization with radiolabeled riboprobes.

Results: We detect 5 distinct splice variants derived from transcription of the CCL27 gene locus. The most abundant form codes for a non-secreted protein, PESKY, and is expressed in lens, cornea, and retina. Another variant corresponds to the mRNA of the secreted chemokine and is synthesized in the cornea, but not in retina or lens. The remaining splice variants are novel and may be eye specific, but have only short open reading frames (<50 amino acids). CCL27 transcripts are most abundantly expressed in the retina, as judged by in situ hybridization.

Conclusions: PESKY and other CCL27 splice variants of unknown function are widely expressed in ocular tissues. Analysis of CCL27 transcripts from lens, retina, and cornea indicates that mRNA for the secreted chemokine, CCL27, is endogenously expressed only in the cornea and may play a role in ocular immune responses involving CD4 lymphocytes in this tissue.