Co-expression of lbe^dsRNA.cMa and lbl^dsRNA.cMa under the control of Scer\GAL4^how-24B results in 3 types of mutant phenotype in the segment border muscles (SBMs) of embryos. Approximately 37% of the embryos show a founder cell migration phenotype, such that the SBM founder is no longer located dorsally, leading to altered SBM shape and ventral accumulation of myoblast nuclei. 50% of the embryos show a myoblast fusion defect characterised by rounded cells close to the SBM. Approximately 13% of the embryos show abnormal attachment of the SBM to adjacent muscles and an abnormal SBM shape.

Expression of lbe^{dsRNA.Scer\UAS} and lbl^{dsRNA.Scer\UAS} in adult myoblasts under the control of Scer\GAL4¹¹⁵¹ results in defects in leg muscle fibres. Mild and severe muscle phenotypes are seen. In the mild phenotype, the muscle mass and the number of muscle fibres is only slightly reduced. In the severe phenotype, leg muscles are significantly smaller and composed of fewer fibres. In both classes of phenotype the deficient muscle fibres are misshaped and adopt irregular rounded or spiracle-like forms surrounding internal tendons. The loss of leg muscle mass is the cause of morphological leg deformations most frequently seen within the femur segment. No changes in the number of twi-expressing cells is seen in these mutants, indicating that lbe and lbl are not involved in myoblast proliferation. All muscle tendons are present in these mutants, although some internal tendons appear reduced, suggesting that their morphogenesis is affected.

Expression of lbe^{dsRNA.Scer\UAS} and lbl^{dsRNA.Scer\UAS} in adult myoblasts under the control of Scer\GAL4¹¹⁵¹ reduces the number of mitochondria associated with the sarcomeric Z line. Myofilaments appear interrupted or irregularly arranged. Also, a reduced intensity of electron-dense desmosomes is visible at the junction between muscle fibers and the internal tendons.

Expression of lbe^{dsRNA.Scer\UAS} and lbl^{dsRNA.Scer\UAS} in adult myoblasts under the control of Scer\GAL4¹¹⁵¹ results in locomotor defects. For example, these mutants cannot perform in a ball rotation assay as well as wild-type flies. Some individuals fail to catch the ball and several of them are unable to maintain it. These flies also exhibit a "shuffling-gait" with a reduced stride-length compared to wild-type.

Expression of lbe^{dsRNA.Scer\UAS} and lbl^{dsRNA.Scer\UAS} in muscle tendons under the control of Scer\GAL4^sr-md710 does not affect muscle development.