COL13A1 and occult macular dystrophy: To investigate the effects of OMD on the mRNA expression of the ECM in HTM cells, the mRNA expression of fibronectin (FN1), collagen type I alpha 1 chain (COL1A1), collagen type I alpha 2 chain (COL1A2), collagen type IV alpha 2 chain (COL4A2), collagen type XII alpha 1 chain (COL12A1), collagen type XIII alpha 1 chain (COL13A1), and collagen type XVIII alpha 1 chain (COL18A1) was quantified using quantitative real-time PCR (Fig 2).