340 R.W. Beuerman, L.K. Goh and V.A. Barathi

Figure 5. Expression of TGM-2 in muscarinic receptor mutant mice sclera.

Significant genes that were shown to have significant differential expression between different time points were selected for gene expression validation. Real time PCR primers were designed using ProbeFinder 2.45 (Roche Applied Science, IN). Mouse 18srRNA gene was used as control due to its constant expression level across the age group.

Summary

These are early stage results and with human studies will require validation in other laboratories. Microarray studies of mouse myopic sclera showed the significant up-regulation of TGM (transglutaminase) 1, 2, 5, MMP-14 (matrix metalloproteinase), 19, Collagen 5a3, a2, MAPK 8, and down-regulation of TGM 3, FBN1 (fibrillin 1) as compared to control sclera after six weeks induction of spectacle lens induced myopia (Ref. 27; Fig. 4). These are all genes with homologies to human gene expression. Previous studies have shown the expression that TGF-beta 1 is downregulated in the tree shrew sclera, which suggested a contribution to greater extensibility.28

Mice with M1 and M5 receptor knock-out expressed more TGM2 in scleral fibroblasts (SF) than knock-outs for M2, M3 in KO and WT mice SFs mRNA levels (Fig. 5). TGM2, also known as tissue transglutaminase, is expressed ubiquitously. The primary function of TGM2 is transamidation and requires calcium as a cofactor. Interestingly,

341 Gene Analysis in Experimental Myopia

transcription is increased by retinoic acid. Amongst its many supposed functions, it appears to play a role in wound healing, apoptosis and extracellular matrix development. However, for its role in the myopic sclera, TG2 also has GTPase activity and in the presence of GTP it is suggested to function as a G protein participating in signaling processes. These results suggest that M1, M5 KO axial growth was higher than the M2, M3 KO and WT mice. Based on these results, TGM2 and muscarinic receptors interaction could be involved in scleral remodeling.

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Section 5

Interventions for Myopia

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