Fig. 6.

Requirement of FGF8-like ligands for the differentiation of specific subgroups of somatic muscles. (A-D) Ventral somatic muscle nuclei (stained for Mef2) in late stage Drosophila embryos. (A) Wild type (wt). Nuclei of ventral oblique (VO) muscles 4-6 are indicated by arrows. VO muscle nuclei are missing in a few hemisegments of ths⁷⁵⁹ homozygotes (B) and in several hemisegments of pyr¹⁸ homozygous (C) and hemizygous (D) embryos (arrowheads) (see also Table 1). (E-K) Myosin heavy chain (Mhc) staining showing somatic muscles in stage 17 embryos. (E-G) Ventrolateral views showing ventral muscles. One or more of VO muscles 4-6 (arrows in E, wild type) are missing in several hemisegments of pyr¹⁸ homozygous (F) or hemizygous (G) embryos (arrowheads). (H-K) Lateral views. Segment border muscles (SBMs) are indicated by arrows in the wild type (H). SBM duplications are observed in both pyr¹⁸ (I) and ths⁷⁵⁹ (J) homozygous mutants (arrowheads), and hemisegments lacking an SBM are also observed in pyr¹⁸ homozygotes (arrowhead in K). (L) Wild-type stage 10 embryo showing Lb expression (green) in the ectoderm and mesoderm. Arrows indicate segmental expression of Lb in the lateral mesoderm. (M) Lb expression in a pyr¹⁸ embryo showing absence of Lb-positive mesoderm cells in one hemisegment (arrowhead).