Fig. 1.

PS1 is expressed by activated and proliferating satellite cells. Myofibres and their associated satellite cells were isolated and either immediately fixed (T0) or cultured in activation medium for either 24 hours (T24), 48 hours (T48) or 72 hours (T72) before fixation. (A) Immunostaining showed that Pax7⁺ satellite cells on freshly isolated myofibres (T0) did not express PS1. (B) PS1 could be detected after activation and during proliferation, as shown by the co-expression of PS1 and Ki67. (C) PS1 was downregulated as satellite-cell-derived myoblasts committed to myogenic differentiation, as demonstrated by the presence of Myog (arrows). (D) Immunocytochemistry on plated satellite-cell-derived myoblasts confirmed that expression of PS1 was associated with proliferating Ki67⁺ cells but not differentiating Myog⁺ cells (arrows). (E) High magnification immunofluorecent image to show the localisation of PS1 in plated satellite-cell-derived cells. (F) Western blot to illustrate that PS1 expression decreases after myogenic differentiation in plated satellite-cell-derived cells. Representative data of at least three independent experiments are shown. Scale bars: 60 μm (A-C), 30 μm (D) and 5 μm (E).