Apc promotes the rapid regulation of Axin following Wingless exposure.

<p>(A-F) Axin accumulates in Wingless-responding cells. Stage 9 embryos expressing <i>Axin-V5</i> driven by the <i>mat-Gal4</i> driver, co-immunostained with V5 and Wg antibodies. By 40 minutes after the onset of Wg exposure, Axin-V5 is distributed in wide segmental stripes (brackets) that overlap the narrow Wg stripes (asterisks). Higher magnification images are shown in (D-F). (G-I) Stage 9 embryos in which <i>Apc2</i> is inactivated both maternally and zygotically and <i>Apc1</i> is reduced zygotically. The genotype of the mother of these embryos is <i>mat-Gal4</i>/UAS-Axin-V5; <i>Apc2</i>^{<i>19</i>.<i>3</i>}<i>/Apc2</i>^{<i>19</i>.<i>3</i>} and the genotype of the father is UAS-Axin-V5/UAS-Axin-V5; <i>Apc2</i>^{<i>19</i>.<i>3</i>} <i>Apc1</i>^<i>Q8</i><i>/TM6B</i>. In contrast with wild-type, Axin-V5 is uniformly increased in all ectodermal cells, indicating Apc is required for the initial accumulation of Axin in Wingless-responding cells.