Fig. 7

Transcriptomic signatures shaped by cell proportion reveal differences in organ development. a A difference in mesenchyme (pink) versus epithelium (blue) proportion in the tooth germ takes part in a transcriptomic signature of organ identity. b Increasing proportion of differentiating cells over time takes part in a transcriptomic signature of developmental time and heterochrony. We evidenced this both in molars (cusp cell differentiation) and limb (chondrogenic cells, see (c) and (d)). c, d We reanalyzed a published transcriptome dataset on forelimb/hindlimb development obtained with microarrays by [27]. On the first axis of PCA, we recovered a strong time-related signal (c) and the expected heterochrony between forelimb and hindlimb (forelimb samples are systematically ahead on PCA1 (c)). Both the time signal and the heterochrony correlated well with the proportion of chondrogenic cell types estimated by deconvolution with a set of marker genes extracted from [102] ((d), compare (c) and (d))