Required for the correct synaptic targeting of motoneurons RP5 and V to muscle 12 (M12) (PubMed:20504957). May be involved in the negative regulation of Tl in M12 (PubMed:20504957). Involved in the correct patterning of veins in the proximal (costal) region of the wing blade (PubMed:17028348). In embryos, expressed specifically in M12 (at protein level). In embryos, M12 position is closer to the ventral nerve cord and situated ventral to muscle 13 (M13) and external to muscle 6/7 (PubMed:20504957). The longitudinal orientation of M12 is also oblique probably due to an alteration in the muscle attachment sites (PubMed:20504957). Also displays a reduced number of synaptic sites on M12. No effect on muscle fiber size (PubMed:20504957). RNAi-mediated knockdown results in the fusion of the costal vein with the L1 vein in the developing wing, producing an adult wing that has a continuous wing margin with no separation between the end of the costal and L1 veins (PubMed:17028348). The medial and distal regions of the costal vein are also fused (PubMed:17028348). Thickening of the costal vein often occurs, and sometimes spans the region between the costal and subcostal veins (PubMed:17028348).