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. 2006 Nov 23;25(24):5826–5839. doi: 10.1038/sj.emboj.7601441

Figure 4.

Figure 4

The TWEAK/Fn14 pathway regulates proliferation and differentiation of primary muscle myoblasts. TWEAK promoted the growth (A–C) and inhibited the differentiation (D, E) of primary myoblasts from wild-type mice. (A–C) After 3 days of proliferation in growth medium, cultures of primary myoblasts treated with 100 ng/ml Fc-TWEAK (B) contained ∼2 × more cells than untreated cultures (A) or cultures treated with both Fc-TWEAK and Fn14-Fc to block receptor function (C). (D, E) After 4 days in low-serum differentiation medium, untreated cultures of primary myoblasts formed multinucleate myotubes (D), whereas myotubes were rarely found in TWEAK-treated cultures (E). (F) Primary myoblasts isolated from Fn14-deficient mice produced fewer progeny than wild-type myoblasts in culture. Results from two independent experiments (exp. no. 1 and exp. no. 2) are shown. In each experiment, myoblasts were obtained from two individual wild-type (WT) and two individual Fn14−/− (KO) mice. Cells were seeded at the same initial cell densities. (G, H) Phase-contrast images of myotubes formed by myoblasts isolated from WT and Fn14-deficient mice.