Fig. 4. VVL expression and loss-of-function effects in developing adult bristles. (A-D) Nuclear expression of VVL in developing bristles in pupal nota. (A) At 16 hours APF VVL expression is observed both in the precursors that have not divided yet and in the two daughter cells. (B) At 24 hours APF, VVL is evenly expressed in the nuclei of all four cells of the developing bristles. (C) By 37-40 hours APF, the expression of VVL decreases in three of the four cells of the organ. (D) At 42 hours APF strong VVL expression is evident in only one cell per organ; this is the socket cell, as indicated by colocalization of VVL (green) and Su(H) (red) (arrow in inset). Weaker expression is occasionally seen in the adjacent shaft cell nucleus (arrowhead). (E-G) Expression in a pupal retina (30 hours APF) of VVL (E), CT (F) and a merge panel (G). Colocalization of the two proteins can be observed in all four cells of the developing interommatidial bristles. Note the lack of VVL expression from the cone cells (arrow in G). (H-N) Cuticle preparations and scanning electron micrographs of wild type (H,M) and vvl mutant clones (I-L,N). (H,I) a2 antennal segments. Note shaft duplications accompanied by two fused sockets in the mutant (arrows). (J-L) Other bristle defects include reduced or missing shafts (black arrowheads in J), distorted shafts (white arrowhead in J), supernumerary sockets (arrows in K) and splitting of shafts (L). The supernumerary sockets can be abnormally flat (arrow in J). (M,N) In the mutant eye, the shafts are dramatically reduced, but the sockets and the distribution of the bristles appear normal. (O,P) Anti-CT staining of developing bristles in wild type (O) and vvl mutant heads (P) at 42 hours APF. Enlarged clusters, containing five or more cells are observed in the mutant, as opposed to only four cells normally (arrows in O and P).

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