Fig. 9. Myofibrillogenesis is delayed in chick skeletal myotubes after treatment with MURF-2 antisense oligonucleotides. Control or MURF-2 antisense-treated myotubes were fixed after 48 or 72 hours of treatment and stained for various sarcomeric components to analyze myofibril assembly. Within 48 hours of treatment, the majority of control myotubes were beginning to assemble -actinin, the M-line region of titin (A168-170), and myosin into regular, striated patterns (a,b,c, double arrows). In contrast, myotubes treated with MURF-2 antisense oligonucleotides were thin and exhibited no myofibril components in striated patterns (d,e,f). Within 72 hours of treatment, both control and MURF-2 antisense treated myotubes contained -actinin, the M-line region of titin, and myosin in regular, striated patterns (g-l, double arrows), although the antisense-treated myotubes still appeared thinner than controls (j-l). Bar,10 µm.