Changes in mRNA levels of the Myoc/Tigr gene in the rat eye after experimental elevation of intraocular pressure or optic nerve transection

PURPOSE. To isolate the rat Myoc/Tigr gene and investigate changes in its e xpression pattern in normal eyes and in eyes with either pressure-induced o ptic nerve damage or optic nerve transection. METHODS. Expression pattern of the rat Myoc/Tigr gene was investigated by N orthern blot hybridization. Optic nerve damage and death of ganglion cells in the retina were induced unilaterally, by injection of hyper-tonic saline solution, episcleral vein cauterization, or optic nerve transection. The l evels of mRNA for Myoc/Tigr were compared between several tissues of the co ntrol and surgically altered eyes, by using semiquantitative RT-PCR. real-t ime PCR, and Northern blot analysis. RESULTS. The rat Myoc/Tigr gene is 10 kb long and contains three exons. Amo ng the eye tissues analyzed, Myoc/Tigr mRNA was detected in the combined ti ssues of the eye angle, sclera, cornea, retina, and optic nerve head. With pressure-induced optic nerve degeneration, the level of Myoc/Tigr mRNA decr eased in the retina and the combined tissues of the eye angle, but increase d in the optic nerve head. After optic nerve transection, the level of Myoc /Tigr mRNA increased in the retina, but did not change in the combined tiss ues of the eve angle. CONCLUSIONS. The decreased level of Myoc/Tigr mRNA in the retina after indu ction of elevated intraocular pressure compared with that in the control re tina cannot be explained by ganglion cell death alone. Differences in Myoc/ Tigr mRNA levels in eye tissues after elevation of intraocular pressure or optic nerve transection may reflect the activation of different signaling p athways involved in regulation of this gene.