Fig. 1.

Articular cartilage exhibits circadian rhythm in protein abundance. A. Heat map of the 48-h time-series experiment showing 145 rhythmic proteins identified by mass spectrometry in mouse hip articular cartilage (MetaCycle integrated P value < 0.05). ZT – Zeitgeber Time (ZT0 = 6 am, lights on; ZT12 = 6 pm, lights off). B. Partial least squares discriminant analysis (PLS-DA) of the rhythmic dataset C. Rose plot showing distribution of peak abundance of rhythmic proteins within the 24-h circadian cycle. Shaded area indicates the dark phase. D. Fold change of protein abundance (by Mass Spec) and gene expression (by RNAseq) of selected molecules in mouse hip articular cartilage. Expression of these genes is affected by disruption of the circadian clock (Col2a1-Cre/ Bmal1 KO). Shaded area indicates the dark phase. E. Representative results confirming changes in protein abundance over a period of 48 h by western blotting in primary mouse chondrocyte culture synchronised by dexamethasone.