Interplay of Light, Melatonin, and Circadian Genes in Skin Pigmentation Regulation
Bibliographic record
Abstract
Abstract Highlights Circadian pigmentation of tadpoles in vivo is mainly driven by melatonin Light and melatonin differentially regulate proliferation Melatonin mimics the expression of circadian core genes in the dark phase Deregulation of the circadian rhythm inhibits melanin synthesis Circadian regulation of skin pigmentation is essential for thermoregulation, UV protection, and synchronization of skin cell renewal. This regulation involves both cell-autonomous photic responses and non-cell-autonomous hormonal control, particularly through melatonin produced in a light-sensitive manner. Photosensitive opsins, cryptochromes, and melatonin regulate circadian rhythms in skin pigment cells. We studied light/dark cycles and melatonin coordination in melanin synthesis and cell proliferation of Xenopus laevis melanophores. In vivo , tadpole pigmentation shows robust circadian regulation mainly hormone-driven, in that isolated melanophores respond strongly to melatonin but only slightly to light. Melanophore proliferation is faster in the dark and slower with melatonin compared to a 12/12 light/dark cycle. Expression of circadian core genes (clock, bmal1, per1, per2, per3, cry1, cry2, and cry4) in melatonin-treated cells during the light phase mimics dark phase expression. Individual Cry overexpression did not affect melanisation or cell proliferation, likely due to functional redundancy. Melanin synthesis was inhibited by circadian cycle deregulation through: a) pharmacological inhibition of Cry1 and Cry2 degradation with KL001, b) continuous light or dark conditions, and c) melatonin treatment. Our findings suggest that circadian cycle regulation, rather than proliferative capacity, alters melanisation of melanophores. Significance Circadian rhythms are a highly conserved phenomenon in nature. In vertebrates, the modification of skin pigmentation and epidermal cell renewal in response to the environmental light-dark cycle are crucial physiological adaptations that serve various purposes, including thermoregulation, reducing ultraviolet damage, and regulating skin stem cell proliferation. Our observations indicate that, in vivo , the circadian regulation of skin pigmentation is more influenced by cycling-melatonin levels than light/dark. The deregulation of the circadian cell cycle through various mechanisms all inhibited melanisation while cell proliferation was increased or reduced, suggesting that proliferation and melanisation are mechanistically dissociated responses. Graphical Abstract
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".