Figure 2. Effects of RNAi-based attenuation of Lb gene function.

A–F Anterior views of tibia A–C and femur D–F musculature revealed in wild type A, D and lbRNAi B, C, E, F flies carrying MHC-tauGFP transgene. B, E show mild phenotypes whereas C, F show severe lbRNAi phenotypes. 3D reconstructions from confocal scans were used to generate the presented views see corresponding 3D videos in Video S3-S8. Muscle fibres from lbRNAi legs are smaller in both ventral arrows in A–C and dorsal arrowheads in A–C tibia. General muscle mass appears reduced in tibia C and femur asterisks in E and F. Loss of muscle mass and the abnormal attachment of muscle fibres to the leg epithelium lead to morphological defects most frequently manifested by bending of the femur segment arrows in E and F. Note also the altered shape of muscle fibers in tadm muscles B, C and tilm muscle E. G RNAi induced reduction in Lbe and Lbl protein levels revealed by Western blot using two different anti-Lb antibodies. Note that a low level of Lbe is still detected in embryos ubiquitously expressing lbRNAi constructs see Materials and Methods for details. H, J Wild type electron microscopy micrographs and I, K micrographs from lbRNAi femur muscles showing H, I sarcomeric ultrastructure and J, K muscle-tendon junction area. The Z line associated pairs of mitochondria dyads, arrows in H are absent in lbRNAi muscle asterisks in I and the few mitochondria still present arrow in I appear to have altered internal structures. Also, myofilaments from lbRNAi sarcomeres are highly disorganised and some of them are disrupted arrowheads in I. A lower intensity electron dense desmosomes are detected in muscle-tendon junctions from lbRNAi legs arrow in K when compared to the wild type arrow in J.