Lxrα mRNA expression determined at ZT0 and ZT 12 in WT males and females using qRT-PCR (A). Diurnal mRNA expression of liver Cyp7α1 was compared in males (B) and females (C) using qRT-PCR in WT (plain line) and Lxrα-/- mice (dashed line). For each time point, 3–4 mice were used. For the Cyp7α1 analysis, cosinor-based non-linear regression was used for curve fitting. The ZT0 time point is double plotted for visualization purposes. Expression data were normalized to the constitutively expressed 36B4 mRNA. The white and black bars represent the light and dark phases, respectively. Statistically significant differences in cosine fitting parameters (p<0.05) between wild type and Lxrα-/- mice or between male and female of the same genotype is indicated in the grey box at the top of the corresponding graph or between graphs (WT: plain arrow, Lxrα-/-: dashed arrow). µ, α and φ indicate a difference in mean level, amplitude and acrophase, respectively.