Fig 1.
Pax7 positive cells migrate into the deep myotome before hatching.
Transverse sections (7 μm) of trout embryos were analyzed by in situ hybridization for pax7 (green) and by immunofluorescence for Collagen 1 (red) at days 14, 19, 21, 24, 26, and 28 post fertilization. Asterisks indicate the dermomyotome-like epithelium and arrowheads indicate pax7+ cells in the deep myotome. The nuclei are counterstained with DAPI and the scale bar corresponds to 100 μm.
Fig 2.
Pax7 positive cells are positioned along muscle fibers before hatching.
Pax7 expression was analyzed by chromogenic in situ hybridization for pax7 on longitudinal sections of 28-dfp trout embryos. Arrowheads indicate pax7+ cells in the deep myotome, adjacent to muscle fibers. The scale bar corresponds to 50 μm.
Fig 3.
Localization of pax7 positive cells in the muscle stem cell niche within the white muscle of trout.
Transverse sections (7 μm) of trout larvae (37, 47, 112 and 136 days post fertilization) were analyzed by in situ hybridization for pax7 (red) and the extracellular matrix was stained with Alexa 488-conjugated wheat germ agglutinin (green). Arrowheads indicate pax7+ cells in the deep myotome. The nuclei are counterstained with DAPI and the scale bar corresponds to 25 μm.
Fig 4.
Expression of pax7 genes increases during white muscle regeneration in trout.
Localization of pax7+ cells (red) in 18-day injured muscle was performed by in situ hybridization (A). The extracellular matrix was stained with wheat germ agglutinin (WGA, green) and the nucleus was stained with DAPI (blue). The asterisks indicate the injury site and the scale bar corresponds to 50 μm. Gene expression profile of pax7a1 (B) and pax7a2 (C) during muscle regeneration in rainbow trout normalized with eF1a expression. Bars represent the standard error and the letters indicate the significant differences between means within the same treatment (control or injured). The asterisk indicates significant differences between treatments at a given point. Statistical significance (p < 0.05) was determined by the Kruskal-Wallis rank test followed by the Dunn test.
Fig 5.
Pax7 positive cells decrease during in vitro differentiation of myogenic progenitors.
Myogenic progenitors were cultured in culture medium (DMEM, 10% SVF) for 7 days. Illustrative images of pax7 (red) and mmx (green) in situ hybridization results performed at day 2 and day 7 of the culture (A). The scale bar corresponds to 50 μm. The percentage of pax7 and myomixer (mmx) positive cells was determined by double in situ hybridization (B). Different capital letters indicate significant differences between means values of mmx positive cells. Different lowercase letters indicate significant differences between means of pax7 positive cells. Different symbols indicate significant differences between means of pax7/mmx positive cells. Statistical significance (p < 0.05) was determined by Kruskal–Wallis rank test followed by Dunn’s test. The scale bar corresponds to 50 μm.