bims-ciryme 2025-04-06 papers

Glia. 2025 Apr 02.

Multi-Omic Analysis Reveals Astrocytic Annexin-A2 as Critical for Network-Level Circadian Timekeeping in the Suprachiasmatic Nucleus.

Andrew P Patton, Toke P Krogager, Elizabeth S Maywood, Nicola J Smyllie, Emma L Morris, Mark Skehel, Michael H Hastings.

The mammalian suprachiasmatic nucleus (SCN) orchestrates daily (circadian) rhythms of physiology and behavior by broadcasting timing cues generated autonomously by its mutually reinforcing network of ~10,000 neurons and ~3000 astrocytes. Although astrocytic control of extracellular glutamate and GABA has been implicated in driving circadian oscillations in SCN gene expression and neuronal activity, the full scale of the network-level signaling mechanisms is unknown. To understand better how this astrocyte-neuron network operates, we adopted a multi-omics approach, first using SILAC-based mass spectrometry to generate an SCN proteome where ~7% of identified proteins were circadian. This circadian proteome was analyzed bioinformatically alongside existing single-cell RNAseq transcriptomic data to identify the cell-types and processes to which they contribute. This highlighted "S100 protein binding," tracked to astrocytes, and revealed annexin-A2 (Anxa2) as an astrocyte-enriched circadian protein for further investigation. We show that Anxa2 and its partner S100a10 are co-expressed and enriched in SCN astrocytes. We also show that pharmacological disruption of their association acutely and reversibly dysregulated the circadian cycle of astrocytic calcium levels and progressively compromised SCN neuronal oscillations. Anxa2 and S100a10 interaction therefore constitutes an astrocytic cellular signaling axis that regulates circadian neuronal excitability and ultimately SCN network coherence necessary for circadian timekeeping.

Keywords: Anxa2; S100a10; SCN; astrocytes; circadian; neurons; proteomics

DOI: https://doi.org/10.1002/glia.70018

FASEB J. 2025 Apr 15. 39(7): e70507

Circadian clock disruption promotes retinal photoreceptor degeneration.

Shumet T Gegnaw, Cristina Sandu, Amandine Bery, Jacoline B Ten Brink, Nemanja Milićević, Aldo Jongejan, Perry D Moerland, Arthur A Bergen, Marie-Paule Felder-Schmittbuhl.

Daily rhythms are a central hallmark of vision, in particular by adapting retinal physiology and light response to the day-night cycle. These cyclic processes are regulated by retinal circadian clocks, molecular machineries regulating gene expression across the 24-h cycle. Although hundreds of genes associated with genetic retinal disorders have been identified, no direct link has been established with the clock. Hence, we investigated the hypothesis that a poorly functioning circadian clock aggravates retinal photoreceptor disease. We performed this study in the P23H rhodopsin-mutated mouse model (P23H Rho) that mimics one major cause of human autosomal dominant retinitis pigmentosa. We also used the rod-specific knockout (rod-Bmal1KO) of Bmal1, a key clock component. More specifically, we used either heterozygous P23H Rho mice or rod-Bmal1KO alone, as well as double mutants of these strains and control mice. We showed by structural (histology, immunohistochemistry) and functional (electroretinography: ERG) analyses that the retinitis pigmentosa phenotype is exacerbated in the double mutant line compared to the P23H Rho mutation alone. Indeed, we observed marked ERG amplitude reduction and more photoreceptor cell loss in double mutants with respect to simple P23H Rho mutants. These observations were further corroborated by transcriptome analysis revealing major gene expression differences between these genotypes. In this data, we identified unique gene expression sets implicating neurogenesis, phototransduction cascade, and metabolism, associated with enhanced photoreceptor degeneration. Thus, our results establish a link between clock dysfunction and retinal degeneration and suggest underlying molecular mechanisms, together providing new concepts for understanding and managing blinding diseases.

Keywords: Bmal1 ; ERG; P23H; RNA‐seq; circadian clock; retinitis pigmentosa; rod

DOI: https://doi.org/10.1096/fj.202401967R

Sci Rep. 2025 Apr 02. 15(1): 11273

Assessment of continuous positive airway pressure effect on the circadian clock signaling pathway in obstructive sleep apnea patients.

Agata Gabryelska, Szymon Turkiewicz, Adrian Gajewski, Julia Jaromirska, Dominik Strzelecki, Piotr Białasiewicz, Maciej Chałubiński, Marcin Sochal.

Obstructive sleep apnea (OSA) is associated with circadian rhythm dysregulation plausibly through affecting clock genes. The study's purpose was to investigate the effect of one-night continuous positive airway pressure treatment (CPAP treatment) on circadian clock genes: BMAL1, CLOCK, CRY1, and PER1 at mRNA and protein levels. The study included 30 OSA patients, who underwent diagnostic polysomnography (PSG) and next a one-night effective CPAP treatment with PSG monitoring (CPAP). The blood was collected in the evening before and the morning after PSG and CPAP. Protein levels and mRNA expression were measured using ELISA and qRT-PCR, respectively. The increase in PER1 expression was observed in the morning after compared to the evening before CPAP (p = 0.005); additionally, PER1 protein level decreased in the morning after CPAP compared to the morning after PSG (p = 0.035). In CLOCK protein levels significant changes were observed: an increase in the morning after CPAP compared to the morning after PSG (p = 0.049), an increase in the morning after CPAP compared to the evening before (p = 0.006), and an increase in difference between the morning after and evening before CPAP vs. difference between morning after and evening before PSG (p = 0.012). Obtained results suggest that even short-term effective CPAP treatment might reverse circadian clock signaling pathway disruption in OSA.

Keywords: Circadian clock; Continuous positive airway pressure (CPAP); Obstructive sleep apnea (OSA); Polysomnography (PSG)

DOI: https://doi.org/10.1038/s41598-025-88834-3

bioRxiv. 2025 Mar 18. pii: 2025.03.18.643991. [Epub ahead of print]

Mitofusin 2 controls mitochondrial and synaptic dynamics of suprachiasmatic VIP neurons and related circadian rhythms including sleep.

Milan Stoiljkovic, Jae Eun Song, Hee-Kyung Hong, Heiko Endle, Luis Varela, Jonatas Catarino, Xiao-Bing Gao, Zong-Wu Liu, Sabrina Diano, Jonathan Cedernaes, Joseph T Bass, Tamas L Horvath.

Sustaining the strong rhythmic interactions between cellular adaptations and environmental cues has been posited as essential for preserving the physiological and behavioral alignment of an organism to the proper phase of the daily light/dark cycle. Here, we show that mitochondria and synaptic input organization of suprachiasmatic (SCN) vasoactive intestinal peptide (VIP)-expressing neurons show circadian rhythmicity. Perturbed mitochondrial dynamics achieved by conditional ablation of the fusogenic protein mitofusin 2 (Mfn2) in VIP neurons cause disrupted circadian oscillation in mitochondria and synapses in SCN VIP neurons leading to desynchronization of entrainment to the light/dark cycle in Mfn2 deficient mice that resulted in advanced phase angle of their locomotor activity onset, alterations in core body temperature and sleep-wake amount and architecture. Our data provide direct evidence of circadian SCN clock machinery dependence on high-performance Mfn2-regulated mitochondrial dynamics in VIP neurons for maintaining the coherence in daily biological rhythms of the mammalian organism.

DOI: https://doi.org/10.1101/2025.03.18.643991

PNAS Nexus. 2025 Apr;4(4): pgaf070

Methamphetamine alters the circadian oscillator and its couplings on multiple scales in Per1/2/3 knockout mice.

Samuel J K Barnes, Mansour Alanazi, Shin Yamazaki, Aneta Stefanovska.

Disruptions to circadian rhythms in mammals are associated with alterations in their physiological and mental states. Circadian rhythms are currently analyzed in the time domain using approaches such as actograms, thus failing to appreciate their time-localized characteristics, time-varying nature and multiscale dynamics. In this study, we apply time-resolved analysis to investigate behavioral rhythms in Per1/2/3 knockout (KO) mice and their changes following methamphetamine administration, focusing on circadian (around 24 h), low-frequency ultradian (around 7 h), high-frequency ultradian (around 30 min), and circabidian (around 48 h) oscillations. In the absence of methamphetamine, Per1/2/3 KO mice in constant darkness exhibited a dominant, ∼7 h oscillation. We demonstrate that methamphetamine exposure restores the circadian rhythm, although the frequency of the methamphetamine sensitive circadian oscillator varied considerably compared to the highly regular wild-type circadian rhythm. Additionally, methamphetamine increased multiscale activity and induced a circabidian oscillation in the Per1/2/3 KO mice. The information transfer between oscillatory modes, with frequencies around circadian, low-frequency ultradian and high-frequency ultradian activity, due to their mutual couplings, was also investigated. For Per1/2/3 KO mice in constant darkness, the most prevalent coupling was between low and high-frequency ultradian activity. Following methamphetamine administration, the coupling between the circadian and high-frequency ultradian activity became dominant. In each case, the direction of information transfer was between the corresponding phases from the slower to faster oscillations. The time-varying nature of the circadian rhythm exhibited in the absence of Per1/2/3 genes and following methamphetamine administration may have profound implications for health and disease.

Keywords: biological oscillators; circadian rhythms; multiscale analysis; nonlinear dynamics; time-resolved analysis

DOI: https://doi.org/10.1093/pnasnexus/pgaf070