When mutant somatic clones are made in border cells, a strong effect is seen on border cell migration. At stage 10 only about 10% of mutant border cell clusters reach the oocyte.

Fusion of myoblasts to form myotubes is virtually absent (development of syncytial muscles is blocked), but muscle founder cells form and later elongate, make epidermal contacts and develop into mononucleate muscles that express differentiated muscle markers. Limited number of neuromuscular synapses form and their ultrastructure is identical to the wild type, EJCs demonstrate the junctions are functional.

Embryos lie motionless in the vitelline membrane and fail to hatch. Examination with polarised light reveals a lack of differentiated muscle. Myoblasts fail to fuse. At 13 to 14 hours of development the myoblasts lie in a segmental array. At 16 to 17 hours of development the myoblasts fall into two populations, stretched and rounded. Stretched myoblasts first appear at around 11 hours after egg laying, and eventually can span distances two or three times the length of normal muscles. They often occur at positions and in orientations reminiscent of wild type muscle precursors. Only very few fusions occur. Segregation and movement of slou-expressing founder cells and vg-expressing cells is normal.