title: Label-free imaging of the native, living cellular nanoarchitecture using partial-wave spectroscopic microscopy.
abstract: The organization of chromatin is a regulator of molecular processes including transcription, replication, and DNA repair. The structures within chromatin that regulate these processes span from the nucleosomal (10-nm) to the chromosomal (>200-nm) levels, with little known about the dynamics of chromatin structure between these scales due to a lack of quantitative imaging technique in live cells. Previous work using partial-wave spectroscopic (PWS) microscopy, a quantitative imaging technique with sensitivity to macromolecular organization between 20 and 200 nm, has shown that transformation of chromatin at these length scales is a fundamental event during carcinogenesis. As the dynamics of chromatin likely play a critical regulatory role in cellular function, it is critical to develop live-cell imaging techniques that can probe the real-time temporal behavior of the chromatin nanoarchitecture. Therefore, we developed a live-cell PWS technique that allows high-throughput, label-free study of the causal relationship between nanoscale organization and molecular function in real time. In this work, we use live-cell PWS to study the change in chromatin structure due to DNA damage and expand on the link between metabolic function and the structure of higher-order chromatin. In particular, we studied the temporal changes to chromatin during UV light exposure, show that live-cell DNA-binding dyes induce damage to chromatin within seconds, and demonstrate a direct link between higher-order chromatin structure and mitochondrial membrane potential. Because biological function is tightly paired with structure, live-cell PWS is a powerful tool to study the nanoscale structure-function relationship in live cells.
authors.affiliation: Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208.
authors.forename: Luay M
authors.initials: LM
authors.lastname: Almassalha
authors.affiliation: Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208.
authors.forename: Greta M
authors.initials: GM
authors.lastname: Bauer
authors.affiliation: Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208.
authors.forename: John E
authors.initials: JE
authors.lastname: Chandler
authors.affiliation: Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208.
authors.forename: Scott
authors.initials: S
authors.lastname: Gladstein
authors.affiliation: Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208.
authors.forename: Lusik
authors.initials: L
authors.lastname: Cherkezyan
authors.affiliation: Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208.
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Stypula-Cyrus
authors.affiliation: Department of Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL 60611.
authors.forename: Samuel
authors.initials: S
authors.lastname: Weinberg
authors.affiliation: Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208.
authors.forename: Di
authors.initials: D
authors.lastname: Zhang
authors.affiliation: Institute of Technology and Innovation, University of Southern Denmark, DK-5230 Odense M, Denmark.
authors.forename: Peder
authors.initials: P
authors.lastname: Thusgaard Ruhoff
authors.affiliation: Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208; Section of Gastroenterology, Boston Medical Center, Boston University School of Medicine, Boston, MA 02118.
authors.forename: Hemant K
authors.initials: HK
authors.lastname: Roy
authors.affiliation: Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208.
authors.forename: Hariharan
authors.initials: H
authors.lastname: Subramanian
authors.affiliation: Department of Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL 60611.
authors.forename: Navdeep S
authors.initials: NS
authors.lastname: Chandel
authors.affiliation: Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208; Department of Chemistry, Northwestern University, Evanston, IL 60208; Chemistry of Life Processes Institute, Northwestern University, Evanston, IL 60208.
authors.forename: Igal
authors.initials: I
authors.lastname: Szleifer
authors.affiliation: Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208; Chemistry of Life Processes Institute, Northwestern University, Evanston, IL 60208 v-backman@northwestern.edu.
authors.forename: Vadim
authors.initials: V
authors.lastname: Backman
mesh_terms: D000818:Animals; D016466:CHO Cells; D002843:Chromatin / Q000737:chemistry; D003412:Cricetulus; D006367:HeLa Cells; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D046911:Macromolecular Substances / Q000737:chemistry; D008853:Microscopy / Q000379:methods*; D057054:Molecular Imaging / Q000379:methods*; D015388:Organelles / Q000737:chemistry
chemical_list: D002843:Chromatin; D046911:Macromolecular Substances
keywords: DNA damage; cell dynamics; chromatin; microscopy; mitochondrial metabolism