Fig. 5: BMP signalling is active in cells displaying a CT/M transcriptional identity and in cells at the muscle/tendon interface in chicken limbs.
From: Unexpected contribution of fibroblasts to muscle lineage as a mechanism for limb muscle patterning
a Violin plots showing Log-normalised expression levels of ID1, ID2 and ID3 genes in cells grouped by their CT (red), CT/M (green) or M (blue) identity at E4, E6 and E10. The statistical test used is a two-sided Wilcoxon rank sum-test; Sample size: n = 4758 cells from two E4 embryos, 3268 cells from three E6 embryos and 21256 cells from three E10 embryos. The exact p-values are indicated on the violin plots. b Bar plot showing the percentage of cells expressing ID genes in CT (red), CT/M (green) or M (blue) cells at E4, E6 and E10. The statistical test used is the two-sided Fisher’s exact test. Sample size: n = 4758 cells from two E4 embryos, 3268 cells from three E6 embryos and 21256 cells from three E10 embryos. The exact p-values are indicated on the graphs. c, d Focus on ventral limb muscle masses from adjacent and transverse limb sections of E6 chicken embryos hybridised with SCX (c) and ID2 (d) probes. e, f Transverse adjacent limb sections of E6 chicken embryos were hybridised with BMP4 probe (e) and immunostained with pSMAD1/5/9 antibody (red) (f). e, f Arrows point to BMP4 and pSMAD1/5/9 expression spots. g, h High magnification of dorsal (g) and ventral (h) limb muscle masses immunostained with pSMAD1/5/9 (red) and MF20 (myosins, green) antibodies and counterstained with DAPI, arrows point to pSMAD1/5/9 expression spots at muscle periphery. i Longitudinal view of a muscle labelled with pSMAD1/5/9 (red) and MF20 (myosins, green) antibodies, arrows point to pSMAD1/5/9 enriched expression at muscle tips. j, k Adjacent and longitudinal limb sections of E7 chicken embryos hybridised with BMP4 (j) or ID2 (k) probes (blue staining), arrow points to ID2 expression at muscle tips close to tendons (labelled with BMP4 and ID2 transcripts). l Longitudinal muscle sections of E9 chicken hybridised with ID2 probe (blue) and immunostained with MF20 antibody (myosins, brown). The arrow points to ID2 expression at muscle tips. High magnification of one muscle tip. m Transverse limb sections of E9 chicken embryos were hybridised with ID2 probe (blue) and immunostained with MF20 (myosins, brown) antibody. Focus on dorsal limb muscles. n Transverse limb sections of E9 chicken embryos immunostained with pSMAD1/5/9 (green) and MF20 (myosins, grey) antibodies. Focus on dorsal limb muscles.
