XOTX2 and XOTX5b differentially synergize with XNRL to activate the rhodopsin promoter and differentially interact in vitro with XNRL. (a) Results of rhodopsin promoter cell transfection assays with several Xotx/otd constructs (with or without Xnrl). Error bars indicate the standard error of the mean. (b) GST-pull down assays compare the interaction of MYC-XOTX/OTD fusion proteins to GST-XNRL or GST alone. The band indicated by an asterisk corresponds to a higher molecular weight (55 kDa) than the one expected for XOTX proteins (41 kDa) and may result from post-translational modification; this needs further investigation. (c) Results of two of these experiments, analyzed by Image J, were statistically processed; columns show the ratio of the retained MYC-tagged proteins relative to their respective input, normalized with respect to the MYC-XOTX2 retained/input ratio. Error bars indicate the standard deviation. The p-value was calculated by bilateral Student's t-test. Asterisks in histograms show statistically significant differences only for more relevant comparisons (*p < 0.05, **p <0.01). (see Additional files 12 and 13 for the full data set).