Fig. 2

Osr1 and Tcf4 identify distinct and common MCT cells. a, b Osr1 expression was assessed by immunolabelling for GFP on E11.5 and E13.5 Osr1 ^GCE/+ embryos. Boxed regions are shown in the numbered panels below and are magnifications of the area. a At E11.5 Osr1 is expressed in limb mesenchyme at the level of the humerus condensation overlapping with Tcf4. Tcf4 is expressed towards the centre and Osr1 towards the periphery of the limb. b At E13.5 Osr1 is expressed in limb mesenchyme in the periphery and encompassing the biceps femoris (bf), gastrocnemius (gc), soleus (so), plantaris (pa), semimembranosus (sm), peroneus longus (pl), extensor digitorum longus (edl) and tibialis anterior (ta) muscles. Tcf4 is expressed in central areas of the limb, where it is exclusive in the flexor digitorum longus (fdl) muscle, and within and surrounding the edl and ta muscles. c E18.5 limb muscle interstitial cells were FACS-isolated as indicated and separated into Osr1-expressing and Osr1-negative (GFP⁺ and GFP⁻) populations. Cytospun cells were labelled for Tcf4 and PDGFRα. Quantification showing the percentages of PDGFRα⁺ and Tcf4⁺ cells in GFP⁺ or GFP⁻ populations is shown below. Percentage of PDGFRα cells in all Tcf4 cells was counted in both GFP⁺ and GFP⁻populations (n = 3). Values represent mean ± s.e.m (n = 3). N-numbers indicate biological replicates, i.e. samples from different specimen