Fig. 4. Muscle and intestinal defects in tbx-8/tbx-9(RNAi) animals. (A-D) Transgenic embryos carrying an hlh-1::GFP body wall muscle reporter. Body wall muscle nuclei are green. (A-B) Embryos around the 400-cell stage. (A) Wild type, dorsal view. Two rows of muscle cells (one on the right and one on the left side of the embryo) are visible at this stage. (B) tbx-8/tbx-9(RNAi) embryo. Some muscle cells are not in regular rows (arrow). (C-D) Embryos at the 1.5-fold stage. (C) Wild type, left lateral view. Muscles have split into dorsal and ventral rows on each side of the embryo. One dorsal and one ventral row can be seen in this focal plane. (D) tbx-8/tbx-9(RNAi) embryo. There is no clear separation of dorsal and ventral rows, especially at the posterior (arrows). (E-F) transgenic animals carrying a myo-3::GFP body wall muscle reporter. (E) Dorsal view of wild-type L1, showing two of the four rows of muscle nuclei; two ventral rows are not visible in this focal plane. (F) Muscle nuclei in tbx-8/tbx-9(RNAi) animals. Instead of lying in straight rows, nuclei are often bunched (arrows), and there are gaps in the row (arrowheads). (G-J) Intestinal defects in tbx-8/tbx-9(RNAi) animals. (G-H) tbx-8/tbx-9(RNAi) animals that have survived to hatching. The intestine has severe morphological defects with the gut lumen being highly distended (arrows). In comparison, a wild-type gut lumen is visible in (E) (arrow). (I-J) Transgenic worms carrying an elt-2::GFP intestinal cell reporter. Intestinal nuclei are green. (I) Wild-type L1 showing the positions of 16 of the 20 intestinal nuclei (the other four are out of focus). (J) tbx-8/tbx-9(RNAi) L1 worm. The intestinal nuclei are out of position, often being bunched together at either end of the intestine (arrows) and missing from the middle (arrowheads). Counting reveals that all nuclei are usually present, however. Posterior is to the right in all panels. Scale bars, 10 µm.