Fig. 3.

Thin is expressed in developing and mature muscle. (A–C) In situ hybridizations showing tn mRNA expression. tn mRNA is robustly expressed in stage 13 (A) and stage 16 (B) WT embryos. Reduction of tn levels is apparent in the l(2)tn/Df mutants (C). (D–L) Thin protein expression in developing muscle (D and E) and mature muscle (G and I). Thin protein accumulated in a muscle-specific pattern in stage 13 (D) and stage 16 (E) WT embryos, but was markedly reduced upon loss of tn function (F). (G) A WT preparation shows that Thin is present in L3 larval muscle (green) in a repeated pattern within the sarcomeres. Costaining for the Z-line protein MLP84B (H, red) reveals that Thin also is found at the Z-disk of the sarcomere (I). Knockdown of tn using RNAi results in a reduction of Thin accumulation at the Z-lines and a general decrease in muscle expression levels (J) compared with MLP84B, which is retained at the Z-lines (K and L). Black arrows (A–F) point to corresponding muscle segments in the developing embryos. White arrows (G–I) illustrate the corresponding Z-lines in the muscle of the L3 larva preparations. (Scale bars, 140 μm for A–F; 15 μm for G–L.)