Fig. 8. Expression of thin filament muscle protein and mRNA are reduced in the absence of TnI. (A) RT-PCR amplification shows decreased thin filament mRNA levels but no reduction in the myosin heavy chain control. (B) Immuno-western blots of IFM proteins from different genotypes show significant reductions in the amount of all the thin filament proteins. Note that arthrin, the IFM-specific, mono-ubiquitinated actin isoform, is missing and that the muscle samples used for the TnI immunoblotting are of whole thoracic proteins to show that the smaller, non-IFM isoform (TnI-E^*) is expressed at normal levels in hdp³ flies, while the IFM-specific isoform (TnI-A^*), present in the Canton-S and Mhc¹² samples, is missing. (C) Immunoblotting of dissected `skinned' IFM samples from wild-type and hdp³; Mhc¹² flies at 40-48, 60-75 hours APF and from adult flies. Ponceau-staining of the glutathione suphuryl transferase 2 (GST-2) band (Clayton et al., 1998) was used to indicate relative protein loadings.