While scientists have long known that many tissues follow these cycles, called circadian rhythms, this is the most comprehensive study connecting timing to gene transcription (the process of copying DNA into RNA to guide protein assembly).
"This is the first time a reference map of daily gene expression has been established," says Satchidananda Panda, a professor in Salk's Regulatory Biology Laboratory and senior author on the paper. "It's a framework to understand how circadian disruption causes diseases of the brain and body, such as depression, Crohn's disease, IBD, heart disease or cancer. This will have huge impact on understanding the mechanisms or optimizing cures for at least 150 diseases."
RNA - Sequencing - Research - Team - Gene
Using RNA sequencing, the research team tracked gene expression in dozens of different non-human primate tissues every 2 hours for 24 hours. The team found that each tissue contained genes that were expressed at different levels based on the time of day. However, the number of these "rhythmic" genes varied by tissue type, from around 200 in pineal, mesenteric lymph nodes, bone marrow and other tissues to more than 3,000 in prefrontal cortex, thyroid, gluteal muscle and others. In addition, genes that were expressed most often tended to show more rhythmicity, or variability by time.
Of the 25,000 genes in the primate genome, nearly 11,000 were expressed in all tissues. Of those (which mostly govern routine cellular functions, such as DNA repair and energy metabolism), 96.6 percent were particularly rhythmic in at least one tissue, varying drastically by when they were sampled.
Tissues - Gene - Transcription - Morning - Afternoon
In most of the tissues, gene transcription peaked in the early morning and late afternoon and quieted in the evening after dinner, around bedtime. With 81.7 percent of protein-coding genes experiencing a rhythmic effect, this timing mechanism is far more widespread than previously suspected.
"These findings provide new insights that could influence how scientific...
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