A cellular basis for the mammalian nocturnal-diurnal switch
File(s)
Author(s)
Type
Journal Article
Abstract
Early mammals were nocturnal while dinosaurs dominated the daytime. Mammalian transition to daytime activity accelerated after the Cretaceous-Paleogene extinction, but the underlying mechanisms remain unclear. We identified a conserved cell-intrinsic, thermodynamic mechanism that likely facilitated this shift. In cells from diurnal mammals, protein synthesis, phosphorylation, and circadian timing were less sensitive to temperature changes than were cells from nocturnal mammals. Comparative genomics revealed accelerated evolution within essential signaling pathways, including mechanistic target of rapamycin (mTOR), that increase the robustness of diurnal cellular clocks to thermal and osmotic perturbation. In nocturnal mice, mTOR inhibition shifted cells, tissues, and behavior toward diurnal activity. These findings uncover a genetic and biochemical basis for nocturnal-diurnal switching, emphasizing how cellular signaling networks can encode complex phenotypes such as temporal niche selection.
Date Issued
2026-02-26
Date Acceptance
2025-11-13
Citation
Science, 2026, 391 (6788)
ISSN
0036-8075
Publisher
American Association for the Advancement of Science (AAAS)
Start Page
eady2822
Journal / Book Title
Science
Volume
391
Issue
6788
Copyright Statement
Copyright © 2026 The Authors. This is the author’s accepted manuscript made available under a CC-BY licence in accordance with Imperial’s Research Publications Open Access policy (www.imperial.ac.uk/oa-policy)
License URL
Identifier
https://www.ncbi.nlm.nih.gov/pubmed/41747039
Subjects
Animals
Female
Humans
Male
Mice
Biological Evolution
Circadian Clocks
Circadian Rhythm
Mice, Inbred C57BL
Phosphorylation
Protein Biosynthesis
Proteomics
Signal Transduction
Suprachiasmatic Nucleus Neurons
Temperature
TOR Serine-Threonine Kinases
Fibroblasts
Publication Status
Published
Coverage Spatial
United States
Article Number
eady2822
Date Publish Online
2026-02-26