title: Super-resolution fluorescence imaging to study cardiac biophysics: α-actinin distribution and Z-disk topologies in optically thick cardiac tissue slices.
abstract: A major motivation for the use of super-resolution imaging methods in the investigation of cardiac biophysics has been the insight from biophysical considerations and detailed mathematical modeling that the spatial structure and protein organisation at the scale of nanometres can have enormous implications for calcium signalling in cardiac muscle. We illustrate the use of dSTORM based super-resolution in optically thick (∼10 μm) tissue slices of rat ventricular tissue to visualize proteins at the cardiac Z-disk and compare those images with confocal (diffraction-limited) as well as electron microscopy (EM) data which still provides a benchmark in terms of resolution. α-actinin is an abundant protein target that effectively defines the Z-disk in striated muscle and provides a reference structure for other proteins at the Z-line and the transverse tubules. Using super-resolution imaging α-actinin labelling provides very detailed outlines of the contractile machinery which we have used to study the properties of Z-disks and the distribution of α-actinin itself. We determined the local diameters of the myo-fibrillar and non-myofibrillar space using α-actinin labelling. Comparison between confocal and super-resolution based myofibrillar masks suggested that super-resolution data was able to segment myofibrils accurately while confocal approaches were not always able to distinguish neighbouring myofibrillar bundles which resulted in overestimated diameters. The increased resolution of super-resolution methods provides qualitatively new information to improve our understanding of cardiac biophysics. Nevertheless, conventional diffraction-limited imaging still has an important role to play which we illustrate with correlative confocal and super-resolution data.
authors.affiliation: Department of Physiology, University of Auckland, Auckland, New Zealand.
authors.forename: Yufeng
authors.initials: Y
authors.lastname: Hou
authors.affiliation: Department of Physiology, University of Auckland, Auckland, New Zealand.
authors.forename: David J
authors.initials: DJ
authors.lastname: Crossman
authors.affiliation: Dept. of Electrical and Electronic Engineering, University of Melbourne, Australia.
authors.forename: Vijay
authors.initials: V
authors.lastname: Rajagopal
authors.affiliation: Department of Physiology, University of Auckland, Auckland, New Zealand; Department of Cell Biology, Yale University, New Haven, USA.
authors.forename: David
authors.initials: D
authors.lastname: Baddeley
authors.affiliation: Biomedical Physics, University of Exeter, UK.
authors.forename: Isuru
authors.initials: I
authors.lastname: Jayasinghe
authors.affiliation: Department of Physiology, University of Auckland, Auckland, New Zealand; Biomedical Physics, University of Exeter, UK. Electronic address: c.soeller@exeter.ac.uk.
authors.forename: Christian
authors.initials: C
authors.lastname: Soeller
mesh_terms: D000185:Actinin / Q000648:ultrastructure*; D000818:Animals; D006352:Heart Ventricles / Q000648:ultrastructure*; D007089:Image Enhancement / Q000379:methods*; D008856:Microscopy, Fluorescence / Q000379:methods*; D057054:Molecular Imaging / Q000379:methods; D020409:Molecular Motor Proteins / Q000648:ultrastructure*; D011487:Protein Conformation; D051381:Rats; D017208:Rats, Wistar; D015203:Reproducibility of Results; D012518:Sarcomeres / Q000648:ultrastructure*; D012680:Sensitivity and Specificity
chemical_list: D020409:Molecular Motor Proteins; D000185:Actinin
keywords: EC coupling; Heart; Microscopy; Myofibril; Super-resolution imaging