Fig. 3. Self-renewing asymmetric division of GMC-1 in nub gain-of-function embryos. (A-D) Embryos stained for Eve; (E-J) embryos double stained for Eve and Spectrin. Arrowhead indicates a GMC-1, arrow indicates an RP2, small arrow indicates a sib. Thin, long arrows (E,G,J) denote indentations indicative of the cell undergoing cytokinesis. (A) 7.75-hour-old wild-type embryo. The GMC-1 has divided to generate a sib and an RP2. (B) 9-hour-old wild-type embryo. Note the fading Eve expression in sib. (C) 7.75-hour-old UAS-nub; ftz-GAL4 embryo. The GMC-1 has divided to generate two cells. (D) 9-hour-old UAS-nub; ftz-GAL4 embryo with a 3-cell phenotype: two sibs and an RP2. (E,F) Wild-type embryos. Both nuclear division and cytokinesis of GMC-1 is asymmetric (E; 7.5-hours old) and this gives rise to the smaller sib and the larger RP2 (F; 8-hours old). (G) 7.5-hour-old UAS-nub; ftz-GAL4 embryo. The GMC-1 is undergoing a nearly equal nuclear division and cytokinesis to self-renew and to generate an RP2. (H) 8.5-hourold UAS-nub; ftz-GAL4 embryo. The GMC-1 is in the process of dividing to generate a smaller sib; an Eve-positive RP2 has already been generated in this hemisegment (the top cell). (I,J) Two different focal planes of the same area of an 8.5-hour-old UAS-nub; ftz-GAL4 embryo, showing a sib cell generated earlier (I) and the GMC-1 dividing to generate two RP2s (J). The long arrow marks the position of the sib. Scale bars: 7.5µm for A-D; 5µm for E-J.