Circadian Oscillation of Gene Expression in Murine Calvarial Bone

Authors

  • Sanjin Zvonic,

    1. Stem Cell Biology Laboratory, Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, Louisiana, USA
    Search for more papers by this author
  • Andrey A Ptitsyn,

    1. Experimental Obesity Laboratory, Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, Louisiana, USA
    Current affiliation:
    1. Center for Bioinformatics, Colorado State University, Ft. Collins, Colorado, USA
    Search for more papers by this author
  • Gail Kilroy,

    1. Stem Cell Biology Laboratory, Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, Louisiana, USA
    2. Tissue Biology Core Facility of the Clinical Nutrition Research Unit, Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, Louisiana, USA
    Search for more papers by this author
  • Xiying Wu,

    1. Stem Cell Biology Laboratory, Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, Louisiana, USA
    Search for more papers by this author
  • Steven A Conrad,

    1. Departments of Bioinformatics and Computational Biology, Medicine, and Emergency Medicine, Louisiana State University Health Sciences Center, Shreveport, Louisiana, USA
    Search for more papers by this author
  • L Keith Scott,

    1. Departments of Bioinformatics and Computational Biology, Medicine, and Emergency Medicine, Louisiana State University Health Sciences Center, Shreveport, Louisiana, USA
    Search for more papers by this author
  • Farshid Guilak,

    1. Division of Orthopaedic Research, Department of Surgery, Duke University Medical Center, Durham, North Carolina, USA
    Search for more papers by this author
  • Gadi Pelled,

    1. Skeletal Biotechnology Laboratory, Hebrew University–Hadassah Medical Center, Jerusalem, Israel
    Search for more papers by this author
  • Dan Gazit,

    1. Skeletal Biotechnology Laboratory, Hebrew University–Hadassah Medical Center, Jerusalem, Israel
    Search for more papers by this author
  • Jeffrey M Gimble MD, PhD

    Corresponding author
    1. Stem Cell Biology Laboratory, Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, Louisiana, USA
    2. Tissue Biology Core Facility of the Clinical Nutrition Research Unit, Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, Louisiana, USA
    • 6400 Perkins Road, Baton Rouge, LA 70808, USA
    Search for more papers by this author

  • Dr Gimble serves as a consultant or collaborator with Artecel, Inc., Vesta Therapeutics, Vet-Stem, Inc., and Zen-BioA, Inc. All other authors state that they have no conflicts of interest.

Abstract

The genes encoding the core circadian transcription factors display an oscillating expression profile in murine calvarial bone. More than 26% of the calvarial bone transcriptome exhibits a circadian rhythm, comparable with that observed in brown and white adipose tissues and liver. Thus, circadian mechanisms may directly modulate oxidative phosphorylation and multiple metabolic pathways in bone homeostasis.

Introduction: Although circadian rhythms have been associated historically with central regulatory mechanisms, there is emerging evidence that the circadian transcriptional apparatus exists in peripheral tissues. The aim of this study was to determine the presence and extent of circadian oscillation in the transcriptome of murine calvarial bone.

Materials and Methods: Cohorts of 8-week-old male AKR/J mice were maintained in a controlled 12-h light:12-h dark cycle on an ad libitum diet for 2 weeks. Groups of three mice were killed every 4 h over a 48-h period. The level of gene expression at successive times-points was determined by quantitative RT-PCR and Affymetrix microarray. Data were analyzed using multiple statistical time series algorithms, including Cosinor, Fisher g-test, and the permutation time test.

Results: Both the positive (Bmal1, Npas2) and negative (Cry1, Cry2, Per1, Per2, Per3) elements of the circadian transcriptional apparatus and their immediate downstream targets and mediators (Dbp, Rev-erbα, Rev-erbβ) exhibited oscillatory expression profiles. Consistent with findings in other tissues, the positive and negative elements were in antiphase relative to each other. More than 26% of the genes present on the microarray displayed an oscillatory profile in calvarial bone, comparable with the levels observed in brown and white adipose tissues and liver; however, only a subset of 174 oscillating genes were shared among all four tissues.

Conclusions: Our findings show that the components of the circadian transcriptional apparatus are represented in calvarial bone and display coordinated oscillatory behavior. However, these are not the only genes to display an oscillatory expression profile, which is seen in multiple pathways involving oxidative phosphorylation and lipid, protein, and carbohydrate metabolism.

Ancillary