Tmod4 but not Tmod3 substitutes for Tmod1 by capping thin filament pointed ends in embryonic muscle. (A–P) Skeletal muscle from Tmod1^+/+ (A–D and I–L) and Tmod1^−/−Tg+ (E–H and M–P) E15.5 mouse embryos stained for F-actin, α-actinin, and either Tmod3 or -4. Tmod3 is diffusely localized, whereas Tmod4 localizes to the pointed ends in the presence or absence of Tmod1. Arrowheads denote H-zones. Bars, 5 µm.