Functional inhibition of the cardiac costamere induces the formation of contraction bands

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Contraction band (CB) necrosis, a key morphological hallmark of ischemia-reperfusion injury, is caused by regional contracture at individual sarcomeres of cardiomyocytes. However, mechanisms for CB formation remain undetermined. We hypothesized that regional ablation of β-dystroglycan (βDG) leads to genesis of CBs at the ablated sites. To address this possibility, we applied multiphoton (MP) excitation-evoked CALI (Tanabe et al., Nat Methods 2005) to neonatal rat hearts transfected with cDNA encoding the protein fused with EGFP (βDG-EGFP), where EGFP fluorescence was homogeneously distributed along the cell membrane. MP-excitation of DG-EGFP at a localized area of interest resulted in instantaneous bleach of EGFP, followed by progressive and localized aggregation of actin filaments at the site of irradiation, consistent with CBs In summary, regional ablation of βDG resulted in formation of CB, suggesting an essential role of this protein in formation of CBs.