Functions as a ligand for integrin alpha-PS2/beta-PS. Required in larvae for proper muscle structure and function. Involved in the regulation of cell adhesion during wing development. Localizes to the basal surface of the dorsoventral cell layer interface during pupal wing development. In embryos, expressed in the apodemes (muscle attachment sites) of the major longitudinal muscles 4, 6, 7, 12 and 13 and the wide dorsal oblique muscles 9 and 10, in hemocytes, in fat body cells, in basement membranes surrounding the gut and in the commissures of the ventral nerve cord. Expressed in larval imaginal wing disk and in pupal wing. In adult flies, expressed in the jump muscle (at protein level). Expressed throughout embryogenesis; first appears at 8-10 hours. Detected in larval and pupal stages (at protein level). Transcripts are first detected at 6-8 hours of development, expression peaks at 12-14 hours and then declines by the end of embryogenesis. O-glycosylation by pgant3 is required for proper secretion and localization to the basal cell layer interface during wing development. Pupal lethal with about 1% escapers. In mutant larvae, muscles 6 and 7 appear stringy and not anchored to other muscles or the epidermis, often these muscles are missing or unrecognizable. Sites where muscles 3, 4, 5, 8 and 16 come together are rarely recognizable and large gaps between muscles 9 and 10 can be observed. Muscle contraction waves that transverse the length of the larvae and are responsible for locomotion are much slower in mutant larvae. Mutant pupae are longer than wild type pupae. Mutant adult flies present elongated abdomen and wings with altered shapes and sizes.