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Thomsen, M.

Publications and source records attributed to Thomsen, M..

11 recordsLinked to original sources
bioRxiv2026

Prime editing enables high-throughput identification and characterization of selective MutSβ inhibitors

DNA mismatch repair (MMR) maintains genome stability but paradoxically drives expansion of pathogenic repeats responsible for trinucleotide repeat disorders. Attenuating repeat instability through targeted inhibition of MMR is therefore a therapeutic strategy of interest; however, progress is constrained by a lack of robust methods for defining and isolating MMR subpathways. We exploited features of prime editing to profile the effects of core MMR genes on thousands of programmed DNA mispairs in cells and resolved distinct MMR processes, including a noncanonical, loop-directed mechanism. Guided by these results, we built a set of scalable reporters that detect loss of separable MMR processes and screened ~72,000 small molecules for activity against MutS{beta}-directed MMR. This effort identified a novel series of MutS{beta} inhibitors that reduced (CAG)n expansion in a cell model. Altogether, this study establishes several methods for systematically interrogating MMR, with demonstrated capacity to identify inhibitors of therapeutic value.

bioengineering↗
bioRxiv2025

Pde10a gates light responses in the SCN to regulate circadian photoentrainment

Light is the principal cue for synchronizing the circadian clock. A common feature of the clock among all organisms is the lack of responsiveness to light during the daytime. To understand the interaction between the circadian clock and light, we described the transcriptome of the suprachiasmatic nucleus (SCN) in mice across different circadian times under both constant darkness (DD) and in response to light exposure. In addition to classifying 10 distinct molecularly-defined SCN neuronal subtypes, we uncovered that SCN exhibits significant transcriptomic responsiveness to light during daytime, the so-called behavioral "dead zone". We further identified Pde10a, a cyclic nucleotide phosphodiesterase, as the first critical component for gating SCN responsiveness to light across the day and thus maintaining robust daily oscillations under regular light-dark conditions.

neuroscience↗
bioRxiv2024

A FAN1 point mutation associated with accelerated Huntington's disease progression alters its PCNA-mediated assembly on DNA

FAN1 is an endo- and exo-nuclease involved in DNA and interstrand crosslink repair. Genome-wide association studies of people with Huntingtons disease revealed a strong association between the FAN1 R507H mutation and early disease onset, however the underlying mechanism(s) remains unclear. FAN1 has previously been implicated in modulating triplet repeat expansion in a PCNA dependent manner. To examine the role of PCNA on FAN1 activation, we solved the cryo-EM structures of a PCNA-FAN1-DNA complex. Our findings reveal that the FAN1 R507 residue directly interacts with PCNA D232. Biophysical interaction studies demonstrated that FAN1 enhances the binding affinity of PCNA for DNA, a synergistic effect disrupted in mutants carrying the R507H mutation. In contrast, PCNA does not affect the affinity of FAN1 for DNA but does modulate FAN1 activity upon ternary complex formation. The weakened and functionally altered FAN1 R507H-PCNA-DNA complex may partly impair the FAN1-mediated repair of CAG extrahelical extrusions, providing a potential explanation for the mutations role in accelerating disease progression.

biophysics↗
bioRxiv2023

Conformational dynamics and DNA recognition by human MutSbeta

Human and mouse genetic studies have demonstrated a role for DNA mismatch repair (MMR) molecular machines in modulating the rate of somatic expansion of the huntingtin (HTT) CAG repeats, and onset and progression of Huntingtons Disease (HD). MutS{beta}, a key component of the MMR pathway, is a heterodimeric protein of MSH2 and MSH3 that recognizes and initiates the repair of extrahelical DNA extrusions. Loss-of-function of mouse Msh3 and reduced-expression alleles of human MSH3 lead to slower rates of somatic expansion and delayed disease onset in humans, signifying MSH3 as a promising therapeutic target for HD. Here we report biochemical and cryo-electron microscopy analyses of human MutS{beta}, demonstrating MutS{beta} undergoes conformational changes induced by nucleotide and DNA binding. We present multiple conformations of MutS{beta} including the DNA-free MutS{beta} compatible with homoduplex DNA binding, two distinct structures of MutS{beta} bound to (CAG)2 DNA, a sliding clamp form and a DNA-unbound, ATP-bound conformation. Along with evidence for novel conformational states adopted by MutS{beta} to initiate the MMR cascade, these structures provide a foundation for structure-guided drug discovery.

biophysics↗
bioRxiv2022

A comprehensive analysis of the gut and skin microbiota in canine atopic dermatitis in Shiba Inu dogs

BackgroundLike its human counterpart, canine atopic dermatitis (cAD) is a chronic relapsing condition; thus, most cAD-affected dogs will require lifelong treatment to maintain an acceptable quality of life. A potential intervention is modulation of the composition of gut microbiota, and in fact, probiotic treatment has been proposed and tried in human atopic dermatitis (AD) patients. Since dogs are currently receiving intensive medical care, this will be the same option for dogs, while evidence of gut dysbiosis in cAD is still missing, although skin microbial profiling in cAD has been conducted in several studies. Therefore, we conducted a comprehensive analysis of both gut and skin microbiota in cAD in one specific cAD-predisposed breed, Shiba Inu. Additionally, we evaluated the impact of commonly used medical management on cAD (Janus kinase; JAK inhibitor, oclacitinib) on the gut and skin microbiota. Furthermore, we genotyped the Shiba Inu dogs according to the mitochondrial DNA haplogroup and assessed its association with the composition of the gut microbiota. ResultsStaphylococcus was the most predominant bacterial genus observed in the skin; Escherichia/Shigella and Clostridium sensu stricto were highly abundant in the gut of cAD-affected dogs. In the gut microbiota, Fusobacteria and Megamonas were highly abundant in healthy dogs but significantly reduced in cAD-affected dogs. The abundance of these bacterial taxa was positively correlated with the effect of the treatment and state of the disease. Oclacitinib treatment on cAD-affected dogs shifted the composition of microbiota towards that in healthy dogs, and the latter brought it much closer to healthy microbiota, particularly in the gut. Additionally, even within the same dog breed, the mtDNA haplogroup varied, and there was an association between the mtDNA haplogroup and gut microbial composition. ConclusionsDysbiosis of both the skin and the gut was observed in cAD in Shiba Inu dogs. Our findings provide a basis for the potential treatment of cAD by manipulating the gut microbiota as well as the skin microbiota.

microbiology↗
bioRxiv2021

Synergistic Effect of Serotonin 1A and Serotonin 1B/D Receptor Agonists in the Treatment of L-DOPA-Induced Dyskinesia in 6-Hydroxydopamine-Lesioned Rats

BackgroundThe gold standard for symptomatic relief of Parkinsons disease is L-DOPA. However, long-term treatment often leads to motor complications such as L-DOPA-induced dyskinesia (LID). While amantadine (Gocovri) is the only approved therapy for dyskinesia in people with Parkinsons disease on the American market, it is associated with neurological side effects and limited efficacy. Thus, there remains a high unmet need for addressing LID in Parkinsons disease patients worldwide. ObjectiveThe objective of this study was to evaluate the efficacy, safety and performance compared to approved treatments of the serotonin receptor 1A (5-HT1A) and 5-HT1B/D agonists buspirone and zolmitriptan in the 6-hydroxydopamine unilaterally lesioned rat model for Parkinsons disease. MethodsThe hemi-parkinsonian 6-OHDA lesioned rats underwent chronic treatment with L-DOPA to induce dyskinesia and were subsequently used for efficacy testing of buspirone, zolmitriptan and comparison with amantadine, measured as abnormal involuntary movement (AIM) scores after L-DOPA challenge. Safety testing was performed in model and naive animals using forelimb adjusting, rotarod and open field tests. Results5-HT1A and 5-HT1B/D agonism effectively reduced AIM scores in a synergistic manner. The drug combination of buspirone and zolmitriptan was safe and did not lead to tolerance development following sub-chronic administration. Head-to-head comparison with amantadine showed superior performance of buspirone and zolmitriptan in the model. ConclusionsThe strong anti-dyskinetic effect found with combined 5-HT1A and 5-HT1B/D agonism renders buspirone and zolmitriptan a potential clinical candidate for LID in Parkinsons disease.

neuroscience↗
bioRxiv2021

Diversity of satellite glia in sympathetic and sensory ganglia

Satellite glia are the major glial type found in ganglia of the peripheral nervous system and wrap around cell bodies of sympathetic and sensory neurons that are very diverse. Other than their close physical association with peripheral neurons, little is known about this glial population. Here, we performed single cell RNA sequencing analysis and identified five different populations of satellite glia from sympathetic and sensory ganglia. We identified three shared populations of satellite glia enriched in immune-response genes, immediate-early genes and ion channels/ECM-interactors, respectively. Sensory- and sympathetic-specific satellite glia are differentially enriched for modulators of lipid synthesis and metabolism. Sensory glia are also specifically enriched for genes involved in glutamate turnover. Further, satellite glia and Schwann cells can be distinguished by unique transcriptional signatures. This study reveals remarkable heterogeneity of satellite glia in the peripheral nervous system.

neuroscience↗
bioRxiv2020

Seagrass beds provide habitat for crabs, shrimps and fish in two estuaries on the South Island of New Zealand

O_LISeagrasses are marine angiosperms that potentially provide habitat for crabs, shrimps and fish. However, these types of data are lacking for the seagrass species (Zostera muelleri/rimur[e]hia) that inhabit intertidal estuaries on the South Island of New Zealand. C_LIO_LIAbundances of crabs, shrimps and fish were therefore quantified from 361 non-destructive seine tows done in seagrass beds and bare mudflats in Duvauchelle bay and two sites in the Avon-Heathcote/Ihutai estuary between October 2019 and February 2020. C_LIO_LIA total of 2549 crabs, 5824 shrimps and 1149 fish (75% were juvenile flounders) were identified and counted in the seine-net and immediately released back in healthy condition to the exact location from where they were caught. C_LIO_LIOnly few seagrass leaves were caught in the net and these leaves may have been previously uprooted drift fragments. The instant catch-and-release methodology therefore leaves, literally, nothing but a footprint. C_LIO_LIMore fish taxa, including two species of pipefish, were found in seagrass beds in Duvauchelle bay than in the Avon-Heathcote estuary. Fish (minus juvenile flounders) were also more abundant in these seagrass beds. Furthermore, juvenile flounders and shrimps were more abundant in Duvauchelle bay compared to the Avon-Heathcote estuary, but were found in similar abundances in seagrass beds and on bare flats. C_LIO_LIIt is possible that more fish were found in Duvauchelle seagrass beds because these beds have adjacent deeper areas, and may have high connectivity to seagrass beds in nearby bays. This hypothesis should be tested by sampling more seagrass beds in different types of estuaries and bays. C_LIO_LIBy contrast, crabs were more abundant in the Avon-Heathcote estuary, where spider crabs were most abundant in the seagrass beds, but other crabs were found in similar abundances in seagrass beds and bare habitat. We hypothesize that crab abundances were higher in the Avon-Heathcote estuary because of lower fish predation pressure and/or larger populations of prey like mollusc and polychaetes. C_LIO_LIOur results suggests that (a) superficially similar Zostera beds in relatively close proximity can provide very different habitat values for fish and crustaceans, (b) seagrass beds with higher diversity and abundances of fish may be prioritized in conservation and management (assuming other important ecosystem functions are similar between beds), and (c) that pipefish may be useful indicator organisms, representing healthy, extensive, dense and connected seagrass beds. C_LI O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=177 SRC="FIGDIR/small/120055v1_ufig1.gif" ALT="Figure 1"> View larger version (111K): org.highwire.dtl.DTLVardef@1c21731org.highwire.dtl.DTLVardef@180c521org.highwire.dtl.DTLVardef@10e2875org.highwire.dtl.DTLVardef@824c21_HPS_FORMAT_FIGEXP M_FIG C_FIG

ecology↗
bioRxiv2020

Identification of SARS-CoV2-mediated suppression of NRF2 signaling reveals a potent antiviral and anti-inflammatory activity of 4-octyl-itaconate and dimethyl fumarate

Antiviral strategies to inhibit Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV2) and the pathogenic consequences of COVID-19 are urgently required. Here we demonstrate that the NRF2 anti-oxidant gene expression pathway is suppressed in biopsies obtained from COVID-19 patients. Further, we uncover that NRF2 agonists 4-octyl-itaconate (4-OI) and the clinically approved dimethyl fumarate (DMF) induce a cellular anti-viral program, which potently inhibits replication of SARS-CoV2 across cell lines. The anti-viral program extended to inhibit the replication of several other pathogenic viruses including Herpes Simplex Virus-1 and-2, Vaccinia virus, and Zika virus through a type I interferon (IFN)-independent mechanism. In addition, induction of NRF2 by 4-OI and DMF limited host inflammatory responses to SARS-CoV2 infection associated with airway COVID-19 pathology. In conclusion, NRF2 agonists 4-OI and DMF induce a distinct IFN-independent antiviral program that is broadly effective in limiting virus replication and suppressing the pro-inflammatory responses of human pathogenic viruses, including SARS-CoV2. One Sentence SummaryNRF2 agonists 4-octyl-itaconate (4-OI) and dimethyl fumarate inhibited SARS-CoV2 replication and virus-induced inflammatory responses, as well as replication of other human pathogenic viruses.

microbiology↗
bioRxiv2019

Mutations in CalDAG-GEFI Lead to Striatal Signaling Deficits and Psychomotor Symptoms in Multiple Species Including Human

Syndromes caused by mutations in Ras-MAP kinase signaling molecules are known as RASopathies and share features such as developmental delay, autistic traits, and cancer. Syndromic features of Rap-MAP kinase signaling defects remain undefined. CalDAG-GEFI is a calcium-responsive Rap-GTPase activator that is enriched in the matrix of the sensorimotor striatum and down-regulated in Huntingtons disease. We show here that CalDAG-GEFI mutations, including striatum-specific deletions and spontaneous mutations in the enzymatic domain, are associated with psychomotor phenotypes in humans, dogs and mice. The identification of these neural mutants was guided by the overt bleeding phenotype in CalDAG-GEFI knockout mice, and then in humans and other species with conserved platelet signaling deficits. Knockout mice exhibit loss of striatal long-term potentiation and deficits in dopamine, acetylcholine and glutamate signaling, along with delayed motor learning and drug-induced perseverative behaviors. Thus, loss of CalDAG-GEFI signaling produces an evolutionarily conserved syndrome characterized by bleeding and psychomotor dysfunction.

neuroscience↗