Biology subjects

Hagen, J.

Publications and source records attributed to Hagen, J..

8 recordsLinked to original sources

bioRxiv2026

Phase-lag-dependent modulation of interhemispheric β-band functional connectivity by dual-site tACS

Dual-site transcranial alternating current stimulation (ds-tACS) is a promising tool for causally manipulating interhemispheric communication; nevertheless, how different stimulation phase-lags selectively modulate functional connectivity (FC) remains unclear. We recruited 29 healthy participants and included 23 in the final analyses. Participants received 20 Hz ds-tACS over the bilateral primary motor cortices (M1s) using four phase-lags (0, pi/2, pi, 3pi/2) and sham stimulation, combined with recording of high-density EEG before and after stimulation. We quantified the interhemispheric FC using the debiased weighted phase-lag index. No significant differences were found in the average FC changes between overall active stimulation and sham. However, the phase-lag associated with maximum absolute FC changes varied substantially across participants. Accordingly, the assessment of phase-lag-dependency of FC using the Kullback-Leibler distance (DKL) revealed a significant phase-lag-dependent modulation of FC that was transient (limited to the first 5 s after stimulation), restricted to frequencies around the stimulation frequency (18-22 Hz), and occurred without corresponding phase-lag-dependent modulation of the spectral power. In an exploratory analysis, the modulation magnitude showed a quadratic relationship with the individual {beta}-peak FC frequency, where participants with {beta}-peak frequencies farther from the 20 Hz stimulation frequency exhibited stronger effects. These findings indicate that ds-tACS can induce time- and frequency-specific modulation of interhemispheric FC across phase-lags. Given the observed association with individual {beta}-peak connectivity frequency and the variability in the phase-lag associated with maximal FC change, our findings motivate further investigation of personalised neuromodulation protocols.

neuroscience↗

bioRxiv2026

RNA-dependent association of the pyruvate dehydrogenase complex with mtDNA-containing assemblies supports mitochondrial translation

Mitochondrial DNA (mtDNA) encodes core subunits of the oxidative phosphorylation machinery, and its expression is spatially organized, with the genome packaged into nucleoids around which transcription and mitoribosome assembly are concentrated. How this architecture is built, and how it is linked to the metabolic state of the organelle, remains poorly understood. Here we show that the pyruvate dehydrogenase complex (PDHc), which supplies acetyl-CoA to the tricarboxylic acid cycle, is a component of this machinery in Saccharomyces cerevisiae. PDHc co-purifies with mtDNA and resides in high-molecular-weight assemblies whose integrity requires RNA rather than DNA, and proximity labeling places it selectively adjacent to the mitoribosome. The E1 subunit Pda1 concentrates into discrete foci that depend on mtDNA and disperse reversibly upon inhibition of mitochondrial translation. Loss of Pda1, Pdb1 or Lat1, but not of the E3-binding protein Pdx1, compromises the maintenance of mtDNA; deletion of PDA1, PDB1 or LAT1 also reduces output from a mitochondrially encoded reporter, and PDHc-deficient cells are hypersensitive to translational inhibition. Catalytically inactive Pda1 and Lat1 variants rescue both defects as effectively as the wild-type proteins, demonstrating a function genetically separable from acetyl-CoA synthesis. PDHc therefore acts as a non-catalytic component of the RNA-dependent architecture that supports mitochondrial gene expression.

cell biology↗

bioRxiv2026

The mitochondrial cohibitin complex facilitates the biogenesis of inner membrane proteins

The inner membrane of mitochondria contains many membrane-embedded carrier proteins of the SLC25 family to facilitate the exchange of metabolites between the cytosol and mitochondria. These carriers use a specific import route for their biogenesis that relies on the TIM22 complex as an inner membrane translocase. The molecular details of carrier biogenesis are not well understood. Using an improved, desthiobiotin-based proximity labeling approach called Destni in living yeast cells, we identified the mitochondrial protein Aim11 as an interactor of newly imported carrier proteins. Aim11 forms a 160 kDa complex together with Iai11, Gep7 and Mtc1 in the mitochondrial inner membrane that we named the comrade-of-prohibitin (cohibitin) complex owing to its genetic interaction with prohibitins. Deletion of Aim11 impairs the import of carrier proteins into the inner membrane and renders cells hypersensitive to carrier overexpression. Our data suggest that the cohibitin complex plays a quality control function that supports the TIM22-mediated insertion of carrier proteins into the inner membrane of mitochondria. SummaryKizmaz et al. identified Aim11 as a novel quality control factor that facilitates the insertion of carrier proteins into the inner membrane of mitochondria. Aim11 is part of the membrane-embedded cohibitin complex which cooperates with prohibitins in inner membrane protein biogenesis.

biochemistry↗

bioRxiv2025

Complement Factor H and its C. elegans homolog regulate IFT52/OSM-6 and CNG channel localization in sensory neurons

Age-related macular degeneration (AMD), the leading cause of blindness in the elderly, is characterized by progressive degeneration of retinal photoreceptors. Current disease models propose AMD pathogenesis is a consequence of cytolytic damage and tissue inflammation that result from defective repression of alternative complement pathway activity by complement factor H (CFH). However, recent studies demonstrate functions for CFH that are outside of its established role in the alternative complement pathway, suggesting that novel CFH-mediated mechanisms may influence AMD initiation and progression. Our previous demonstration that CFH and its nematode homolog, CFH-1, modulate inversin/NPHP-2 accumulation in vertebrate photoreceptor and C. elegans sensory neuron cilia during aging suggests that AMD patients with CFH loss-of-function mutations have cilia defects that may contribute to photoreceptor dysfunction. Here, we investigate the consequences of CFH and CFH-1 loss-of-function mutations on the dynamics and localization of intraflagellar transport (IFT) train and visual cycle components in these cells. In C. elegans sensory neurons, IFTB1 components IFT52/OSM-6 and IFT88/OSM-5 are transported at similar rates in WT animals but IFT52/OSM-6 transport slows significantly in cfh-1 mutant animals while IFT88/OSM-5 is unaffected. Defective localization of IFT52/OSM-6 in photoreceptors of CFH knockout mice and in human photoreceptors from AMD high-risk CFH Y402H homozygotes, suggest an evolutionarily conserved role for CFH in promoting IFT52/OSM-6 transport and localization in sensory neuron cilia. In addition, distribution of CNG channel subunits in C. elegans cfh-1 mutant sensory neurons and CFH Y402H high-risk human photoreceptors are distinct from their WT and Y402 low-risk counterparts. Together, the data indicate previously unappreciated functions for CFH in IFT train organization and cilia protein localization and suggest a novel mechanism for photoreceptor segment thinning, an early AMD biomarker that has been linked to CFH high-risk variants.

cell biology↗

bioRxiv2023

Pan-tissue mitochondrial phenotyping reveals lower OXPHOS expression and function across tumor types

Targeting mitochondrial oxidative phosphorylation (OXPHOS) to combat cancer is increasingly being investigated using a variety of small molecule inhibitors. Clinical success for these inhibitors has been hampered due to serious side-effects potentially arising from the inability to discriminate between non-cancerous and cancerous mitochondria. Although mitochondrial oxidative metabolism is essential for malignant growth, mitochondria OXPHOS is also essential to the physiology of all organs, including high-energy-demand organs like the heart. In comparing tumor OXPHOS reliance to these preeminent oxidative organs it is unclear if a therapeutic window for targeting mitochondrial OXPHOS in cancer exists. To address this gap in knowledge, mitochondrial OXPHOS was comprehensively evaluated across various murine tumors and compared to both matched normal tissues and other organs. When compared to both matched normal tissues, as well as high OXPHOS reliant organs like heart, intrinsic expression of the OXPHOS complexes, as well as OXPHOS flux were consistently lower across distinct tumor types. Operating on the assumption that intrinsic OXPHOS expression/function predicts OXPHOS reliance in vivo, these data suggest that pharmacologic blockade of mitochondrial OXPHOS likely compromises bioenergetic homeostasis in healthy oxidative organs prior to impacting tumor mitochondrial flux in a clinically meaningful way. Although these data caution against the use of indiscriminate mitochondrial inhibitors for cancer treatment, considerable heterogeneity was observed across tumor types with respect to both mitochondrial proteome composition and substrate-specific flux, highlighting the possibility for targeting discrete mitochondrial proteins or pathways unique to a given tumor type.

biochemistry↗

bioRxiv2022

Gene editing in the nematode parasite Nippostrongylus brasiliensis using extracellular vesicles to deliver active Cas9/guide RNA complexes

Despite recent advances, animal-parasitic nematodes have thus far been largely refractory to genetic manipulation. We describe here a new approach providing proof of principle that CRISPR/Cas9-mediated gene editing of parasitic nematodes is achievable using vesicular stomatitis virus glycoprotein-pseudotyped extracellular vesicles (EV) for the delivery of Cas9-synthetic guide RNA (RNP) complexes. We demonstrate that EV-delivered RNPs can be used to disrupt a secreted DNase II in Nippostrogylus brasiliensis. Introduction of a repair template encoding multiple stop codons led to measurable reduction in expression of the targeted gene. Altered transcripts corresponding to the edited locus were detected by RT-PCR, demonstrating that vesicles can access cells of tissues actively expressing the gene of interest. These data provide evidence that this technique can be employed for targeted gene editing in N. brasiliensis, making this species genetically tractable for the first time and providing a new platform for genetic analysis of parasitic nematodes. Author SummaryParasitic nematodes have a complex life cycle involving passage through a host organism, which makes them very difficult to manipulate genetically. Recently, a method for deleting, changing or replacing genes (gene editing) has been developed in other organisms which has revolutionised our ability to understand fine details of how these organisms work. It has generally not been possible to adapt this method to parasitic nematodes because delivery of the components is difficult, and this has proved to be a bottleneck in understanding how parasites develop, survive and interact with their host. We show here that the components for gene editing can be introduced into a widely used laboratory model of intestinal nematode infection by encapsulation in membrane-bound vesicles which have been modified to carry a protein which facilitates fusion of the vesicles with parasite cells and delivery of the contents. This resulted in accurate editing of a specific gene by deletion and repair, such that the amount of functional protein produced from that gene was reduced. This system should be applicable to all nematode species, and will facilitate understanding of their complex biology, in addition to defining new targets for control of infection.

molecular biology↗

bioRxiv2021

Caldendrin represses neurite regeneration via a sex-dependent mechanism in sensory neurons

Caldendrin is a calmodulin-like Ca2+ binding protein that is expressed primarily in neurons and regulates multiple effectors including Cav1 L-type Ca2+ channels. Here, we tested the hypothesis that caldendrin regulates Cav1-dependent pathways that repress neurite growth in dorsal root ganglion neurons (DRGNs). By immunofluorescence, caldendrin was localized in medium- and large-diameter DRGNs. Consistent with an inhibitory effect of caldendrin on neurite growth, neurite initiation and growth was enhanced in dissociated DRGNs from caldendrin knockout (KO) mice compared to those from wild type (WT) mice. In an in vitro axotomy assay, caldendrin KO DRGNs grew longer neurites via a mechanism that was more sensitive to inhibitors of transcription as compared to WT DRGNs. Strong depolarization, which normally represses neurite growth through activation of Cav1 channels, had no effect on neurite growth in DRGN cultures from female caldendrin KO mice. Remarkably, DRGNs from caldendrin KO males were no different from those of WT males in terms of depolarization-dependent neurite growth repression. We conclude that caldendrin opposes neurite regeneration and growth, and this involves coupling of Cav1 channels to growth-inhibitory pathways in DRGNs of females but not males. Our findings suggest that caldendrin KO mice represent an ideal model in which to interrogate the transcriptional pathways controlling neurite regeneration and how these pathways may differ in males and females.

neuroscience↗

bioRxiv2020

Taenia larvae possess distinct acetylcholinesterase profiles with implications for host cholinergic signalling

Larvae of the cestodes Taenia solium and Taenia crassiceps infect the central nervous system of humans. Taenia solium larvae in the brain cause neurocysticercosis, the leading cause of adult-acquired epilepsy worldwide. Relatively little is understood about how cestode-derived products modulate host neural and immune signalling. Acetylcholinesterases, a class of enzyme that degrade acetylcholine, are produced by a host of parasitic worms to aid their survival in the host. Acetylcholine is an important signalling molecule in both the human nervous and immune systems, with powerful modulatory effects on the excitability of cortical networks. Therefore, it is important to establish whether cestode derived acetylcholinesterases may alter host neuronal cholinergic signalling. Here we make use of multiple techniques to profile acetylcholinesterase activity in different extracts of both Taenia crassiceps and Taenia solium larvae. We find that the larvae of both species contain substantial acetylcholinesterase activity. However, acetylcholinesterase activity is lower in Taenia solium as compared to Taenia crassiceps larvae. Further, whilst we observed acetylcholinesterase activity in all fractions of Taenia crassiceps larvae, including on the membrane surface and in the excreted/secreted extracts, we could not identify acetylcholinesterases on the membrane surface or in the excreted/secreted extracts of Taenia solium larvae. Finally, using whole-cell patch clamp recordings in rat hippocampal brain slice cultures, we demonstrate that Taenia larval derived acetylcholinesterases can modify neuronal responses to acetylcholine. Together, these findings highlight the possibility that Taenia larval acetylcholinesterases can interfere with cholinergic signalling in the host, potentially contributing to pathogenesis in neurocysticercosis. Author summaryInfection of the human nervous system with larvae of the parasite Taenia solium is a significant cause of acquired epilepsy worldwide. Despite this, the precise cellular and molecular mechanisms underlying epileptogenesis in neurocysticercosis remain unclear. Acetylcholinesterases are a family of enzymes widely produced by helminthic parasites. These enzymes facilitate the breakdown of acetylcholine, which is also a major neurotransmitter in the human nervous system. If T. solium larvae produce acetylcholinesterases, this could potentially disrupt host cholinergic signalling, which may in turn contribute to seizures and epilepsy. We therefore set out to investigate the presence and activity of acetylcholinesterases in T. solium larvae, as well as in Taenia crassiceps larvae, a species commonly used as a model parasite in neurocysticercosis research. We found that both T. crassiceps and T. solium larvae produce acetylcholinesterases with substantial activity. We further demonstrate that the acetylcholinesterase activity in the products of these parasites is sufficient to disrupt cholinergic signalling in an ex vivo brain slice model. This study provides evidence that Taenia larvae produce acetylcholinesterases and that these can interfere with cholinergic signalling in the host and potentially contribute to pathogenesis in neurocysticercosis.

neuroscience↗