(A) Map of the meru (CG32150) locus, showing the predicted cut sites of the two gRNA pairs (1 and 2) used to generate two different deletions, and the three predicted meru transcripts (RA, RC and RD). meru coding sequences are highlighted in orange, untranslated regions in black, the neighboring gene, CG15715 and the micro RNA mir-263b within the first intron of meru in grey. meru1, derived from gRNA pair 1 (marked in red), has exons 2, 3 and part of exon 4 excised. meru2, derived from gRNA pair 2 (marked in blue), lacks exon 1. (B) Genomic PCRs with primers flanking the meru locus performed on DNA from meru mutants or control flies confirming the length of the deletions. (C) RT-PCR on mRNA from meru mutants or control flies showing that truncated transcripts are still expressed for both deletions. meru1 was positive for transcript expression of the 5’ UTR and exon 1, and meru2 for expression of exons 2 to 4. (D) Wing of an adult fly outlining the stout bristle region on the anterior wing margin (highlighted in teal). The black box outlines the region of the close-up images from Figure 1 and Figure 3. (E) Schematic of the affected macrochaetes (highlighted in purple) in meru1 mutants. The Wingless expression pattern is highlighted in green, adapted from (Simpson, 2007). (F–G’’) Third instar wing imaginal discs stained for Meru (purple) and Hindsight (green). Meru is found exclusively in SOP cells (F–F’’) and not detectable in wing discs of meru1 mutants (G–G’’). Scale bar = 50 µm. (H–H’) hsFLP-induced mitotic clones of meru1 stained for Meru (purple). Wild type tissue is GFP positive and meru1 mutant tissue GFP negative (outlined with a green dashed line in H’). Scale bar = 10 µm.