Fig. 8. Notch signalling and founder cell numbers. (A) Wild-type preparation of 24-hour APF duf-lacZ pupa (grown at 29°C). The box outlines duf-lacZ-expressing founders of DVM I fibres. (B) The duflacZ founders of DVM I (present within the outlined region in A) shown at a higher magnification. (C,D) duf-lacZ-expressing DVM I founders in animals expressing dnNotch (C) and MamN (D). The number of founders is unchanged. The relative orientation of the three duf-lacZ-expressing cells with respect to each other varies slightly in B, C and D. Such variation is also observed in wild-type preparations. (E,F) 22C10 staining in the dorsal A4 hemisegment of a N^ts1pupa grown entirely at permissive temperatures (E) and of a heat-pulsed N^ts1 pupa (F), grown for 24 hours at 22°C and then pulsed for 4 hours and 36 minutes at non-permissive temperature (see Materials and methods for details). The small arrows indicate the 22C10-stained cells, whose number (20 in this case) remains unchanged despite reduced Notch function in N^ts1 pupae. (G) A 12-hour APF preparation from a duf-lacZ-expressing pupa (grown at 29°C), showing the wild-type pattern of founders in DVMs and DLMs. The three black asterisks indicate the three DVM I founders, while the red asterisks show the two founders corresponding to DVM II. The arrow indicates duf-lacZ nuclei belonging to the larval template adjacent to the DVMs. (H) duf-lacZ expression in a pupa (similar age to that in G) in which Nintra has been expressed in all myoblasts. DVM founders are missing in these pupae. Bold asterisks mark the region where the founders are expected. (I) duf-lacZ expression in a 1151Gal4/UAS-Twi pupa. Constitutive expression of Twist in the myoblasts results in an absence of DVM founders. (J-L) Complementary expression pattern of duf-lacZ and Twist in the myoblasts. (J) Confocal section of Twist-expressing myoblasts in the presumptive region of formation of DVM II. (K) Same image as that in J showing duf-lacZ-expressing founders of DVM II. (L) Merged image showing the absence of Twist immunoreactivity in the duflacZ-expressing nuclei. Anterior is to the top, dorsal midline to the right. Scale bars: in A, 9 µm; in B, 9 µm for B-D: in E, 25 µm for E,F; in I, 20 µm for G-I; in J, 15 µm for J-L.