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Reposted by Fidel Serrano

Luísa Tupinambá Jabbur @jabbur.bsky.social · 09/09/2024

Incredibly proud to share this work, almost 6 years in the making, out this month in Science!!! 🎇 We've known for over a century that eukaryotes of all kinds anticipate the seasons (think: hibernation, flowering, reproduction!), but what about bacteria?🦠 www.science.org/doi/10.1126/...

science.org

Bacteria can anticipate the seasons: Photoperiodism in cyanobacteria

Photoperiodic time measurement is the ability of plants and animals to measure differences in day versus night length (photoperiod) and use that information to anticipate critical seasonal transformat...

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Reposted by Fidel Serrano

Joanna Chiu @joanna-chiu.bsky.social · 19/06/2026

Join us!! Ask experts on how to promote health and get better sleep by strengthening your circadian rhythms. We are celebrating the inaugural World Circadian Day on June 24 by holding an "Ask Me Anything" on Reddit 🌍 🌎 🌏 👏 #SRBR #CSC #ACS #InSC #EBRS #CSBR #JSC #CCBM #biologicalrhythms #sleep

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Reposted by Fidel Serrano

Waggoner Lab @labwaggoner.bsky.social · 19/06/2026

Independent of sequence, disordered regions promote the stable chromatin occupancy required for pioneer-factor activity www.science.org/doi/10.1126/...

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Reposted by Fidel Serrano

Mike Dorrity @mwdorr.bsky.social · 19/06/2026

First pre-print from the lab, a collaborative effort led by Jess Bourn @bournsupremacy.bsky.social, a fantastic PhD in my group. We resolve a key problem in development + evolution: how do we quantify heterochrony and link temporal variation to phenotype? www.biorxiv.org/content/10.6...

biorxiv.org

Quantitative mapping of heterochrony to species-specific phenotypes

The genetic program of animal development is conserved, but its rate of execution varies across species. Heterochrony, shifts in the relative timing of developmental events, generates phenotypic varia...

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Fidel Serrano @fidelserrano.bsky.social · 15/06/2026

P.S. We are fully aware of the limitations of our overexpression approach and have always tried to design our experiments in a way that they are tightly-controlled. Nevertheless, we think these mechanisms can enrich our understanding of how the circadian repressive phase is organized. ⏰

elifesciences.org

Nuclear CK1δ as a critical determinant of PER:CRY complex dynamics and circadian period

Repressive PER2:CRY1:CK1δ complexes assembling in the cytosol enter the nucleus, where PER2 hyperphosphorylation eventually disrupts the complex, causing PER2 to relocalize to the cytoplasm, allowing ...

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Fidel Serrano @fidelserrano.bsky.social · 15/06/2026

9/9 Finally, we saw that only the nuclear pool of CK1d could affect circadian period (with the cytoplasmic pool having no effect) further suggesting that this phosphorylation-mediated disruption of PER2-CRY1 interaction may serve as a transition mechanism from the early to the late repressive phase.

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Fidel Serrano @fidelserrano.bsky.social · 15/06/2026

8/9 Interestingly, these cytoplasmic PER2:CRY1:CK1d complexes could serve to buffer nuclear CRY1 protein concentrations, an important mechanism to consider when the clock needs to sustain sufficient CRY1 expression in the late repressive phase long after CRY1 mRNA expression has been repressed.

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Fidel Serrano @fidelserrano.bsky.social · 15/06/2026

7/9 Assembling the full PER2:CRY1:CK1d complex by overexpression, these complexes were cytoplasmic and contained less CRY1. This suggested that CK1d-driven PER2 phosphorylation may disrupt PER2-CRY1 interaction, potentially a novel mechanism to transition from the early to the late repressive phase.

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Fidel Serrano @fidelserrano.bsky.social · 15/06/2026

6/9 Overall, PER2 serves its known role as the stabilizing scaffold for the repressive complex bringing together CRY1 and CK1d; CRY1 determines the nuclear (and therefore effective) concentration of the complex; and CK1d seems to be a late entrant into the full circadian repressive complex.

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Fidel Serrano @fidelserrano.bsky.social · 15/06/2026

5/9 Consequently, since active CK1d is rapidly degraded, when PER2 begins to be expressed (i.e., in a circadian manner), it may take some time for interaction between PER2 and CK1delta to occur, stabilize the kinase, and assemble CK1d into the complex.

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Fidel Serrano @fidelserrano.bsky.social · 15/06/2026

4/9 Knowing that the full repressive complex contains PER2, CRY1, and CK1d, we then asked when is CK1delta assembled into this complex? This line of inquiry also gave an interesting result: when CK1d is overexpressed, it showed that it was regulated dependent on kinase activity.

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Fidel Serrano @fidelserrano.bsky.social · 15/06/2026

3/9 This project began with the initial observation that when we overexpressed fluorescently-tagged PER2 and CRY1 in our U2OStx cells, they formed these interesting dynamic foci in the nucleus. Interestingly, the subcellular localization of these foci was dependent on the relative PER:CRY ratio

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Fidel Serrano @fidelserrano.bsky.social · 15/06/2026

2/9 The repressive phase is subdivided into early and late phases, distinguished by circadian time, complex composition, and mechanism of repression. Early complex has PERs, CRYs, and CK1’s all bound to BMAL1:CLOCK; late complex contains only CRY1 bound to and directly repressing BMAL1:CLOCK.

pnas.org

PNAS

Proceedings of the National Academy of Sciences (PNAS), a peer reviewed journal of the National Academy of Sciences (NAS) - an authoritative source of high-impact, original research that broadly spans...

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Fidel Serrano @fidelserrano.bsky.social · 15/06/2026

1/9 Our publication is now out on eLife! In this study, we became interested in how the circadian repressive phase is organized in circadian time and subcellular space, focusing on the main mammalian circadian repressors: PER2, CRY1, and CK1delta (CK1d). elifesciences.org/articles/110...

elifesciences.org

Nuclear CK1δ as a critical determinant of PER:CRY complex dynamics and circadian period

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Fidel Serrano @fidelserrano.bsky.social · 14/02/2025

Contributing this to the scientific, specifically circadian field! 🕕 Bluesky-orial to follow! 🦋

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Fidel Serrano @fidelserrano.bsky.social · 14/02/2025

Contributing this to the scientific, specifically circadian field! Bluesky-orial to follow! 🦋

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