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S. Chakravarti, F. Wu, N. Vij, L. Roberts; Microarray Gene Expression Profile of the Mouse Cornea Compared to Other Tissues: Clues for Unique Structure and Functions of the Cornea . Invest. Ophthalmol. Vis. Sci. 2003;44(13):866.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The cornea is a unique connective tissue that provides physical support, protection against external pathogens, clarity and almost 70% of the refractive power for optimal vision. To identify genes in the cornea that specifically contribute to this diversity of functions we sought to establish a cornea specific gene expression pattern. Methods: Total RNA from the cornea, tendon and colon of 2-month-old mice (CD-1 out-bred strain, Charles River) were probed with MG_U74Av2 microarrays (Affymetrix) to identify genes expressed differentially in the cornea and tendon compared to the colon (Lawrance, 2001 Hum. Mol. Gen. 10:445). The Microarray analysis software (Affymetrix) was used to analyze gene expression patterns. The DNA-chip cluster algorithm was used for hierarchical clustering of differentially expressed genes (Li, 2001 PNAS. 98:31). Expression of select genes was confirmed by real time RT-PCR. Results: As connective tissues, the tendon and the cornea have many similarities, apparent when contrasted to the colon gene expression. At the >= 5-fold change, using colonic gene expression as baseline, 417 genes were differentially expressed in the cornea and tendon; 116 of these were common to both. Notably, collagen types I, V, VI, lumican, and to a lesser extent keratocan, was up regulated in the cornea and tendon. A comparison of the cornea and the tendon showed major differences in the following functional groups (number of genes per cluster in parenthesis): cell growth (38); maintenance (103), cell communication (46), enzymes (51), immune response (13), ECM and cell adhesion (21). The crystallins that contribute to lens and corneal refractive properties were up regulated specifically in the cornea. Other up regulations in the cornea were keratin 12, transcription factor Pax 6, p53 apoptosis effectors, structural proteins Collagen type VII, laminin a3, down regulation included genes for procollagen XI, TIMP2, procollagen XV and elastin. Additionally, in the cornea, 22 unknown genes/ESTs were differentially expressed. Conclusion: Gene expression profiling of the cornea and tendon has identified genes and biological pathways that are common to these two collagen-rich connective tissues and additional known and novel genes uniquely expressed in the cornea. Comparing gene expression patterns of the cornea with other non-cornea tissues have elucidated global changes that are likely to contribute to transparency, avascularity, cell growth regulation, extracellular matrix organization and neurosensory properties of the cornea.
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