Scer\GAL4^Mef2.PU sing^GD3396 pharate adults show a considerable reduction in muscle mass compared to wild type: no skeletal muscles are consistently observed in the mutants, except for small, partially developed dorsal longitudinal muscles. The nuclei in the mutant muscles are often clustered together and always fewer in number compared to the homogenously dispersed nuclei of wild type. These phenotypes are attributed to a myoblast fusion defect at the stage following the formation of F-actin foci.

Expression of sing^GD3396 in just the muscle founder cells using Scer\GAL4^kirre-rP298, or in just the fusion competent myoblasts using Scer\GAL4^sns.PK, results in 100% viable adults with normal muscle formation. However, expression of sing^GD3396 simultaneously in muscle founder cells and fusion competent myoblasts using both Scer\GAL4^kirre-rP298 and Scer\GAL4^sns.PK is lethal, with pharate muscle showing a clear reduction in the number of nuclei per muscle, indicating reduced myoblast fusion.

Adults expressing sing^GD3396 under the control of Scer\GAL4^elav.PLu (in the presence of Dcr-2^Scer\UAS.cDa to increase the efficiency of RNAi) do not show a significant defect in avoidance of noxious temperature (46[o]C) compared to control flies.

Expression under the control of Scer\GAL4^Mef2.PR results in late pupal lethality.

Expression under the control of Scer\GAL4^pnr-MD237 results in bristle morphology defects on the notum in 20-30% of the Scer\GAL4^pnr-MD237 expression domain.