Gene expression analysis of human epidermal keratinocytes cultured in the presence or absence of Y-27632. Adult human keratinocytes were cultured for several passes in the presence or absence of 10 μM Y-27632. RNA was isolated at passage 3 and passage 4 and was analysed for gene expression by microarray analysis. A. The major gene ontology (GO) categories up-regulated (blue arrow) and down-regulated (red arrow) are shown. Additional file 2: Table S2 shows the complete list of statistically significantly changed GO categories. B. A comparison of significantly (P <0.05) down-regulated genes from this study with genes encoded by the epidermal differentiation complex . The genes common to both categories are listed to the right. C. A comparison of genes from this study down-regulated at least two-fold by Y-27632 with genes up-regulated by ROCK 2 and associated with keratinocyte differentiation as described by McMullan et al. . The genes common to both categories are listed to the right. D. The microarray data were further analysed for differential gene expression using the R software package Limma  and are presented as a heatmap with hierarchical clustering. Down-regulated genes are shown in orange and up-regulated in blue. The list of differentially expressed genes is listed in Additional file 1: Table S1.