Figure 3
TAGLN is expressed in PPF fibroblasts and diaphragm muscle cells. (a–d) whole mount nLacz staining of diaphragm explant from Tagln-Cre:Rosa26NGZ at embryonic and postnatal stages. Tagln-Cre labels the PPF (asterisk in a), septum transversum (dotted area in b,c) and developing diaphragm muscles, while in the postnatal diaphragm this labelling is restricted to the muscular component. (e–l) Transverse sections in the PPF region of the developing embryonic diaphragm and adult diaphragm in Tagln-Cre:Rosa26tdTom mouse model. (e,f) The PPF at E11.5 contains TAGLN + Tcf4+ myofibroblasts and does not express signal for MyoD or Pax7 yet. (g) At E12.5 the tdTomato + cells are fibroblasts expressing Tcf4 and are positioned at the advancing edge of the diaphragm. While myogenic cells are located at the centre of the developing diaphragm. (h) At E13.5 TAGLN is upregulated at the leading edge of the developing diaphragm (arrow). (i) tdTomato+ cells at the leading edge of the developing diaphragm express TGFβR2. (j) Dorsal diaphragm cells (tdTomato+) start to downregulate TAGLN from E13.5. (k,l) Myotubes are marked by tdTomato, indicating their developmental origin from TAGLN+ myoblasts. TAGLN expression is limited to the perivascular space but not in the diaphragm muscle cells of the adult diaphragm. The dotted area in b,c represents the edges of the septum transversum and in e,f the PPF. Tagln-Cre signal in (e) was removed to enhance visualization of TAGLN antibody signal. CT: central tendon, ST: septum transversum. Scale bars: 500 µm in (a–d) 100 µm & insets 50 µm in (e–l).
