Open AccessQuantitative live imaging of Venus::BMAL1 in a mouse model reveals complex dynamics of the master circadian clock regulator
Author(s) -
Nan Yang,
Nicola J. Smyllie,
Honor Morris,
Cátia F. Gonçalves,
Michal Dudek,
Dharshika Pathiranage,
Johanna E. Chesham,
Antony Adamson,
David G. Spiller,
Egor Zindy,
James Bagnall,
Neil Humphreys,
Judith A. Hoyland,
Andrew Loudon,
Michael H. Hastings,
QingJun Meng
Publication year - 2020
Publication title -
plos genetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.587
H-Index - 233
eISSN - 1553-7404
pISSN - 1553-7390
DOI - 10.1371/journal.pgen.1008729
Subject(s) - circadian rhythm , biology , circadian clock , suprachiasmatic nucleus , bacterial circadian rhythms , cryptochrome , microbiology and biotechnology , regulator , oscillating gene , light effects on circadian rhythm , neuroscience , master clock , genetics , gene , electrical engineering , clock signal , electronic circuit , engineering
Evolutionarily conserved circadian clocks generate 24-hour rhythms in physiology and behaviour that adapt organisms to their daily and seasonal environments. In mammals, the suprachiasmatic nucleus (SCN) of the hypothalamus is the principal co-ordinator of the cell-autonomous clocks distributed across all major tissues. The importance of robust daily rhythms is highlighted by experimental and epidemiological associations between circadian disruption and human diseases. BMAL1 (a bHLH-PAS domain-containing transcription factor) is the master positive regulator within the transcriptional-translational feedback loops (TTFLs) that cell-autonomously define circadian time. It drives transcription of the negative regulators Period and Cryptochrome alongside numerous clock output genes, and thereby powers circadian time-keeping. Because deletion of Bmal1 alone is sufficient to eliminate circadian rhythms in cells and the whole animal it has been widely used as a model for molecular disruption of circadian rhythms, revealing essential, tissue-specific roles of BMAL1 in, for example, the brain, liver and the musculoskeletal system. Moreover, BMAL1 has clock-independent functions that influence ageing and protein translation. Despite the essential role of BMAL1 in circadian time-keeping, direct measures of its intra-cellular behaviour are still lacking. To fill this knowledge-gap, we used CRISPR Cas9 to generate a mouse expressing a knock-in fluorescent fusion of endogenous BMAL1 protein (Venus::BMAL1) for quantitative live imaging in physiological settings. The Bmal1 Venus mouse model enabled us to visualise and quantify the daily behaviour of this core clock factor in central (SCN) and peripheral clocks, with single-cell resolution that revealed its circadian expression, anti-phasic to negative regulators, nuclear-cytoplasmic mobility and molecular abundance.