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Fig. 2. Tmod4 and Lmod3 localize to the M-line during
Xenopus skeletal myofibrillogenesis. The somite regions of
Xenopus embryos were sectioned and protein distribution was
examined using Texas-Red-conjugated phalloidin and antibodies
against a-actinin, Tmod4 or Lmod3. (A–L) Localization of Tmod4
protein during skeletal muscle myofibrillogenesis. (A–D) At st20,
continuous actin filament staining was visible (A), with no periodic
localization of a-actinin (B) or Tmod4 staining (C). (E–H) At st24,
diffuse striations were visible in a small number of actin filaments
(E). In these striated regions, narrow bands of a-actinin (F,
arrowheads) and Tmod4 staining (G, arrows) were visible. (I–L) At
st34, broad sharply striated (i.e. highly organized) actin filaments
(I) were observed throughout the skeletal muscle tissue. Sharp
regions of a-actinin (J, arrowheads) and Tmod4 staining (K) were
visible at the Z-disc and M-line regions, respectively. (M–X)
Localization of Lmod3 protein during skeletal muscle
myofibrillogenesis. (M–P) At st20, continuous actin filament
staining was visible, but no localization of a-actinin (N) or Lmod3
(O) was observed. (Q–T) At st24, some regions of developing
muscle showed narrow diffusely striated actin filaments (Q). In
these regions, narrow bands of a-actinin (R, arrowheads) and
Lmod3 staining (S, arrows) were visible. (U–X) At st34, broad
sharply striated actin filaments were visible throughout the
developing somites. Staining for a-actinin (V, arrowheads) and
Lmod3 (W, arrows) was detected at the Z-line and M-line regions,
respectively. We conclude that both Tmod4 and Lmod3 proteins
are present at the M-line region of the sarcomere from the earliest
stages of myofibril assembly. Scale bar: 5 mm. |
