Signaling in pterygium. Schematic representation of potential signaling pathways involved in primary pterygium. These pathways could be affected in conjunctival epithelial cells, fibroblasts or vascular endothelial cells. Pathways were identified by incorporating the microarray results (genes which were differentially expressed between normal conjunctival and pterygium tissue) into Pathway Studio. Green symbols represent down-regulation, whereas red symbols represent up-regulation of genes. Solid lines represent positive regulation, thin arrow with a cross line represent inhibition. Purple symbols represent intermediate molecules in the potential pathways that may have altered function, for example, CDKN1A or p21 (Cip) may have reduced function due to down-regulated egr1 transcription factor. GP75: Tyrosinase-related protein 1, CSTA: cystatin A, TAGLN: transgelin, GJA1: Gap junction protein α-1 or Connexin-43, ABCA1: ATP binding cassette subfamily A1 protein, CEL: carboxyl ester lipase, DUSP1: dual specificity phosphatase I, PMAIP1: phorbol-12-myristate-13-acetate-induced protein 1, BTG2: B cell translocation gene 2, CYP26A1: cytochrome P450 family 26 A1 isoform, NR4A1 and 4A2: nuclear receptors 4A1 and 2, SPARC: secreted protein acidic rich in cysteine, TGM-2: transglutaminase 2, TFPI-2: Tissue factor pathway inhibitor 2 and IGFBP3: insulin-like growth factor binding protein 3. Green symbols within the nucleus represent transcription factors genes that were depressed, probably due to the upstream stress signaling such as those related to ultraviolet light (not shown). Due to quenching effect, there may be an increased in the transcriptional promoter activity of other transcription factors such as SP1, CEBP and SP3 (open symbols).