Fig. 3. An FGF pathway regulates muscle membrane extension. (A-D) Disruption of egl-15, let-756 and let-60 results in numerous EMEs. (E-H) The EMEs of sem-5(RNAi) worms (see Fig. 1H) are suppressed by clr-1(e1745) loss of function and let-60(n1046) gain of function, neither of which displays significant EMEs on their own. (A-H) Red arrows indicate individual EMEs, green arrows indicate intact lateral BWM membranes. (I-M) A dorsal right-hand side view of adult worms, showing BWMs numbers 9, 11, 13 (green arrowhead) and 15 [right to left, according to our numbering scheme (Dixon and Roy, 2005)], extending muscle arms (red arrowheads) to the dorsal nerve cord (blue arrowheads). (J) clr-1(e1745); trIs30 worms extend significantly fewer muscle arms to the nerve cord than do controls. (K) sem-5(RNAi); trIs30 worms extend muscle arms normally and display EMEs (yellow arrowheads). (L,M) The MAD phenotype of clr-1(e1745) worms is partially rescued in the background of sem-5(RNAi) (L) and fully rescued in the background of egl-15(n1783) (M). Scale bar: in A, 50 µm for A-H; in I-M, 50 µm.