Fig. 2

Prediction of chronological age from a mouse epigenetic clock. a Flow chart to illustrate the steps taken in defining the model and testing it. Datasets are displayed as segments of a circle. They are coloured to correspond with later figures, namely: Reizel in brown (R), Cannon in green (C), Babraham in purple (B), Zhang in pink (Z) and Schillebeeckx in light green (S). The two independent datasets are displayed as segments in a separate circle to those datasets utilised for the training phase. The flow of methylation data is shown as colour-coded lines. Training occurs at the node (screen) with the caption: ‘glmnet’. The chosen CG sites and their corresponding weighting are passed on to the prediction tool itself (node with the caption: ‘epigenetic age predictor’. Test data enter this prediction tool and age predictions are outputted, as displayed by the pocket watches exiting this node. b Scatter plot depicting weight of chosen clock sites against their age-associated correlation, blue are negatively correlated sites and orange are positively correlated sites. c Training set ages as predicted by the model, x-axis shows the actual age and y-axis shows the predicted age, coloured by tissue. Jitter is used to represent the experimental error in age estimates. d Test set ages as predicted by the model, x-axis shows the actual age and y-axis shows the predicted age, coloured by tissue. e Box plot of the absolute error in the training (left) and test (right) samples. The median absolute error is indicated. f Principal component representation of the sites used in the clock, coloured by age in weeks