Food-entrained rhythmic expression of PER2 and BMAL1 in murine megakaryocytes does not correlate with circadian rhythms in megakaryopoiesis.
BACKGROUND
Circadian rhythms control a vast array of biological processes in a broad spectrum of organisms. The contribution of circadian rhythms to the development of megakaryocytes and the regulation of platelet biology has not been defined.


OBJECTIVE
This study tested the hypothesis that murine megakaryocytes exhibit hallmarks of circadian control.


METHODS
Mice expressing a PER2::LUCIFERASE circadian reporter protein and C57BI/6 mice were used to establish if megakaryocytes expressed circadian genes in vitro and in vivo. Mice were also subjected to 3 weeks on a restricted feeding regime to separate food-entrained from light-entrained circadian rhythms. Quantitative real time polymerase chain reaction (PCR), flow cytometry and imunohistochemistry were employed to analyse gene expression, DNA content and cell-cycle behavior in megakaryocytes collected from mice over a 24-h period.


RESULTS
Megakaryocytes exhibited rhythmic expression of the clock genes mPer2 and mBmal1 and circadian rhythms in megakaryopoiesis. mPer2 and mBmal1 expression phase advanced 8 h to coincide with the availability of food; however, food availability had a more complex effect on megakaryopoiesis, leading to a significant overall increase in megakaryocyte ploidy levels and cell-cycle activity.


CONCLUSIONS
Normal megakaryopoiesis requires synchrony between food- and light-entrained circadian oscillators.
Hartley
P S
PS
Centre for Cardiovascular Science, Queens Medical Research Institute, The University of Edinburgh, Edinburgh, UK. p.s.hartley@ed.ac.uk
John Sheward
W
W
French
K
K
Horn
J M
JM
Holmes
M C
MC
Harmar
A J
AJ
D056930:ARNTL Transcription Factors; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics*; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000235:genetics*; D002940:Circadian Rhythm / Q000235:genetics; D004435:Eating / Q000235:genetics / Q000502:physiology*; D004920:Erythropoiesis; D005502:Food; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D008533:Megakaryocytes / Q000166:cytology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009687:Nuclear Proteins / Q000235:genetics*; D056950:Period Circadian Proteins; D010507:Periodicity; D014157:Transcription Factors / Q000235:genetics*
D056930:ARNTL Transcription Factors; D051792:Basic Helix-Loop-Helix Proteins; D018797:Cell Cycle Proteins; D009687:Nuclear Proteins; D056950:Period Circadian Proteins; D014157:Transcription Factors; C538961:Bmal1 protein, mouse; C513312:Per2 protein, mouse