SPRR1A and keratoconus: qPCR analysis revealed comparable regulation of differentiation-associated proteins (keratin 5 and 10, filaggrin and loricrin; Fig. 2a), cell junction components (tight junction protein 1, claudin 1, occludin and desmocollin 1; Fig. 2b) and factors associated with desquamation and cornification (transglutaminase 1, small proline rich proteins 1 A and 2 G and serine protease inhibitor Kazal-type 5 SPINK5; Fig. 2c) during the differentiation process of primary KC and SVTERT KC.