Fig. 6

Phenotypes of de novo sarcomere assembly in the ttn.2/1-null mutant. (A) WT or ttn^xu071 mutant embryos at the 18-somite stage were stained for α-Actinin. The images were taken at the 6th, 12th and 15th somites (ST). Scale bar: 5 μm. Z-bodies were scattered as irregular dots (open arrowheads) at the 15th somites and became periodic and aligned longitudinally (solid arrowheads) at the 12th somite. In the 6th somite, Z-bodies underwent lateral growth to form striated Z-disks (arrows) in WT embryos but not in the ttn^xu071 mutant (solid arrowheads). (B) The width of the Z-disc of WT and ttn^xu071 mutants at the 6th somite was quantified. Means±s.d. N=90 for each group from six embryos. **P<0.01. (C) The length of sarcomeres, marked by the distance between two adjacent Z-bodies or Z-disks, in 6th, 12th and 15th somites of WT and ttn^xu071 mutant embryos. The length of sarcomeres did not increase at the 6th somite in the ttn^xu071 mutant compared with WT, where sarcomere length increased to 2.2 µm. Means±s.d. ***P<0.00001. N=80 for each group in different somites from six embryos. n.s., not significant (P>0.05).