A new neutrophil subset promotes CNS neuron survival and axon regeneration.

Transected axons typically fail to regenerate in the central nervous system (CNS), resulting in chronic neurological disability in individuals with traumatic brain or spinal cord injury, glaucoma and ischemia-reperfusion injury of the eye. Although neuroinflammation is often depicted as detrimental, there is growing evidence that alternatively activated, reparative leukocyte subsets and their products can be deployed to improve neurological outcomes. In the current study, we identify a unique granulocyte subset, with characteristics of an immature neutrophil, that had neuroprotective properties and drove CNS axon regeneration in vivo, in part via secretion of a cocktail of growth factors. This pro-regenerative neutrophil promoted repair in the optic nerve and spinal cord, demonstrating its relevance across CNS compartments and neuronal populations. Our findings could ultimately lead to the development of new immunotherapies that reverse CNS damage and restore lost neurological function across a spectrum of diseases.

Sufficient conditions for rapid range expansion of a boreal conifer.

Unprecedented modern rates of warming are expected to advance boreal forest into Arctic tundra1, thereby reducing albedo2-4, altering carbon cycling4 and further changing climate1-4, yet the patterns and processes of this biome shift remain unclear5. Climate warming, required for previous boreal advances6-17, is not sufficient by itself for modern range expansion of conifers forming forest-tundra ecotones5,12-15,17-20. No high-latitude population of conifers, the dominant North American Arctic treeline taxon, has previously been documented5 advancing at rates following the last glacial maximum (LGM)6-8. Here we describe a population of white spruce (Picea glauca) advancing at post-LGM rates7 across an Arctic basin distant from established treelines and provide evidence of mechanisms sustaining the advance. The population doubles each decade, with exponential radial growth in the main stems of individual trees correlating positively with July air temperature. Lateral branches in adults and terminal leaders in large juveniles grow almost twice as fast as those at established treelines. We conclude that surpassing temperature thresholds1,6-17, together with winter winds facilitating long-distance dispersal, deeper snowpack and increased soil nutrient availability promoting recruitment and growth, provides sufficient conditions for boreal forest advance. These observations enable forecast modelling with important insights into the environmental conditions converting tundra into forest.

The herpesvirus UL49.5 protein hijacks a cellular C-degron pathway to drive TAP transporter degradation.

The transporter associated with antigen processing (TAP) is a key player in the major histocompatibility class I-restricted antigen presentation and an attractive target for immune evasion by viruses. Bovine herpesvirus 1 impairs TAP-dependent antigenic peptide transport through a two-pronged mechanism in which binding of the UL49.5 gene product to TAP both inhibits peptide transport and triggers its proteasomal degradation. How UL49.5 promotes TAP degradation has, so far, remained unknown. Here, we use high-content siRNA and genome-wide CRISPR-Cas9 screening to identify CLR2KLHDC3 as the E3 ligase responsible for UL49.5-triggered TAP disposal. We propose that the C terminus of UL49.5 mimics a C-end rule degron that recruits the E3 to TAP and engages the cullin-RING E3 ligase in endoplasmic reticulum-associated degradation.

RNA degradation in human mitochondria: the journey is not finished.

Mitochondria are vital organelles present in almost all eukaryotic cells. Although most of the mitochondrial proteins are nuclear-encoded, mitochondria contain their own genome, whose proper expression is necessary for mitochondrial function. Transcription of the human mitochondrial genome results in the synthesis of long polycistronic transcripts that are subsequently processed by endonucleases to release individual RNA molecules, including precursors of sense protein-encoding mRNA (mt-mRNA) and a vast amount of antisense noncoding RNAs. Because of mitochondrial DNA (mtDNA) organization, the regulation of individual gene expression at the transcriptional level is limited. Although transcription of most protein-coding mitochondrial genes occurs with the same frequency, steady-state levels of mature transcripts are different. Therefore, post-transcriptional processes are important for regulating mt-mRNA levels. The mitochondrial degradosome is a complex composed of the RNA helicase SUV3 (also known as SUPV3L1) and polynucleotide phosphorylase (PNPase, PNPT1). It is the best-characterized RNA-degrading machinery in human mitochondria, which is primarily responsible for the decay of mitochondrial antisense RNA. The mechanism of mitochondrial sense RNA decay is less understood. This review aims to provide a general picture of mitochondrial genome expression, with a particular focus on mitochondrial RNA (mtRNA) degradation.

Proteoglycan 4 (PRG4) treatment improves skin wound healing in a porcine model.

Proteoglycan 4 (PRG4) is a boundary lubricant originally identified in articular cartilage and has been since shown to have immunomodulation and antifibrotic properties. Previously, we have demonstrated that recombinant human (rh)PRG4 treatment accelerates auricular cartilage injury closure through an inhibition of the fibrotic response, and promotion of tissue regeneration in mice. The purpose of the current study was to examine the effects of rhPRG4 treatment (vs. a DMSO carried control) on full-thickness skin wound healing in a preclinical porcine model. Our findings suggest that while rhPRG4 did not significantly accelerate nor impede full-thickness skin wound closure, it did improve repair quality by decreasing molecular markers of fibrosis and increasing re-vascularization. We also demonstrated that rhPRG4 treatment increased dermal adipose tissue during the healing process specifically by retaining adipocytes in the wound area but did not inhibit lipolysis. Overall, the results of the current study have demonstrated that rhPRG4 acts as antifibrotic agent and regulates dermal adipose tissue during the healing processes resulting in a tissue with a trajectory that more resembles the native skin vs. a fibrotic patch. This study provides strong rationale to examine if rhPRG4 can improve regeneration in human wounds.

Suicide gene-enabled cell therapy: A novel approach to scalable human pluripotent stem cell quality control.

There are an increasing number of cell therapy approaches being studied and employed world-wide. An emerging area in this field is the use of human pluripotent stem cell (hPSC) products for the treatment of injuries/diseases that cannot be effectively managed through current approaches. However, as with any cell therapy, vast numbers of functional and safe cells are required. Bioreactors provide an attractive avenue to generate clinically relevant cell numbers with decreased labour and decreased batch to batch variation. Yet, current methods of performing quality control are not readily scalable to the cell densities produced during bioreactor scale-up. One potential solution is the application of inducible/controllable suicide genes that can trigger cell death in unwanted cell types. These types of approaches have been demonstrated to increase the quality and safety of the resultant cell products. In this review, we will provide background on these approaches and how they could be used together with bioreactor technology to create effective bioprocesses for the generation of high quality and safe hPSCs for use in regenerative medicine approaches.

Decorating phenylalanine side-chains with triple labeled 13C/19F/2H isotope patterns.

We present an economic and straightforward method to introduce 13C-19F spin systems into the deuterated aromatic side chains of phenylalanine as reporters for various protein NMR applications. The method is based on the synthesis of [4-13C, 2,3,5,6-2H4] 4-fluorophenylalanine from the commercially available isotope sources [2-13C] acetone and deuterium oxide. This compound is readily metabolized by standard Escherichia coli overexpression in a glyphosate-containing minimal medium, which results in high incorporation rates in the corresponding target proteins.

Towards cost-effective side-chain isotope labelling of proteins expressed in human cells.

Side chain isotope labelling is a powerful tool to study protein structure and interactions by NMR spectroscopy. 1H,13C labelling of side-chain methyl groups in a deuterated background allows studying large molecules, while side-chain aromatic groups are highly sensitive to the interaction with ligands, drugs, and other proteins. In E. coli, side chain labelling is performed by substituting amino acids with isotope-labelled precursors. However, proteins that can only be produced in mammalian cells require expensive isotope-labelled amino acids. Here we provide a simple and cost-effective method to label side chains in mammalian cells, which exploits the reversible reaction catalyzed by endogenous transaminases to convert isotope-labelled α-ketoacid precursors. We show by in-cell and in-lysate NMR spectroscopy that replacing an amino acid in the medium with its cognate precursor is sufficient to achieve selective labelling without scrambling, and how this approach allows monitoring conformational changes such as those arising from ligand binding.

13 Cß-Valine and 13 Cγ-Leucine Methine Labeling To Probe Protein Ligand Interaction.

Precise information regarding the interaction between proteins and ligands at molecular resolution is crucial for effectively guiding the optimization process from initial hits to lead compounds in early stages of drug development. In this study, we introduce a novel aliphatic side chain isotope-labeling scheme to directly probe interactions between ligands and aliphatic sidechains using NMR techniques. To demonstrate the applicability of this method, we selected a set of Brd4-BD1 binders and analyzed 1 H chemical shift perturbation resulting from CH-π interaction of Hß -Val and Hγ -Leu as CH donors with corresponding ligand aromatic moieties as π acceptors.

Pixel walking along the boreal forest-Arctic tundra ecotone: Large scale ground-truthing of satellite-derived greenness (NDVI).

In this Technical Advance, we describe a novel method to improve ecological interpretation of remotely sensed vegetation greenness measurements that involved sampling 24,395 Landsat pixels (30 m) across 639 km of Alaska's central Brooks Range. The method goes well beyond the spatial scale of traditional plot-based sampling and thereby more thoroughly relates ground-based observations to satellite measurements. Our example dataset illustrates that, along the boreal-Arctic boundary, vegetation with the greatest Landsat Normalized Difference Vegetation Index (NDVI) is taller than 1 m, woody, and deciduous; whereas vegetation with lower NDVI tends to be shorter, evergreen, or non-woody. The field methods and associated analyses advance efforts to inform satellite data with ground-based vegetation observations using field samples collected at spatial scales that closely match the resolution of remotely sensed imagery.

Impact of commissural alignment on the hemodynamic performance of supra-annular self-expandable transcatheter aortic valves.

BACKGROUND: Hemodynamic impact of commissural alignment (CA) with self-expandable transcatheter aortic valves (TAVR) has not been investigated yet. AIMS: To determine hemodynamic impact of CA with self-expandable TAVR. METHODS: Multicentric ambispective study comparing patients who underwent self-expandable TAVR in seven centers with the Evolut Pro/Pro+ (EP) (Medtronic) and Acurate neo2 (AN2) (Boston Scientific) with and without CA strategies. The degree of commissural misalignment (CMA) was assessed by computed tomography/angiography and 1-year transvalvular gradients/regurgitation evaluated by echocardiography. A matched comparison according to annular dimensions/eccentricity, prosthesis size/type, and baseline left ventricular function and gradients was performed. RESULTS: A total of 557 patients, mean age 80.7 ± 6.6 years, 61.4% men, and STS score of 4.3 ± 3.1% were analyzed. A CA technique was attempted in 215 patients (38.6%), including 113 patients with AN2 and 102 patients with EP. None/mild CMA was found in 158 (73.5% vs. 43.6% if no CA attempted, p < 0.001) with no differences between devices (AN2:75.2%; EP:71.6%, p = 0.545). Patients with moderate/severe CMA had a greater aortic peak gradient (22.3 ± 8.7 vs. 19.7 ± 8.5, p = 0.001), significantly greater progression of both peak (p = 0.002) and mean gradients (p = 0.001) after matching, and higher rate of central aortic regurgitation (1.2% vs. 0.4%, p = 0.005) at 1-year, but not a greater proportion of patients with mean gradient ≥ 10 mmHg. CONCLUSIONS: The use of CA strategies significantly reduced the rate of CMA for the self-expandable TAVR devices ACN2 and EP which was associated to lower transvalvular gradients and intra-prosthetic regurgitation progression at 1-year although no criteria of structural deterioration were met at this follow up. CLINICALTRIALS: org: NCT05097183.

Different prognostic significance of coronary artery and aortic valve calcium in patients with chest pain.

OBJECTIVES: Coronary artery calcification (CorCa) identifies high cardiovascular risk in the general population. In this setting, aortic valve calcification (AoCa) showed contradictory results. Our goal has been to assess the prognostic power of CorCa and AoCa in patients with chest pain who underwent an ECG-gated cardiac multidetector CT (cardiac-MDCT). METHODS: A total of 528 patients without previous known coronary artery disease, with chest pain who underwent a cardiac-MDCT multidetector, were retrospectively recruited. The primary endpoint included death, acute coronary syndrome, stroke, and heart failure. RESULTS: A total of 61 patients (11.6%) had an event during a mean follow-up of almost 6 years (5.95 ± 2.98). The most frequent event was acute coronary syndrome (6.4%). Total mortality was 4.5%. Patients with CorCa > 0 had more events than those without CorCa (17.3% versus 4.3%; p < 0.001). Likewise, when only patients without AoCa were considered (n = 118), clinical events were more frequent in those with CorCa (12.7% versus 3.6%; p = 0.004). After excluding patients with coronary artery disease, events were more frequent in those with CorCa (12.6% versus 4.3%; p = 0.004). The higher the Agatston score, the more frequent the events. Patients with AoCa > 0 had more events than those without (16.5% versus 7.3%; p < 0.001), but in patients without CorCa, no difference in events was seen (6.2% versus 3.6%; p = 0.471). A Cox regression analysis showed age, smoking, prior stroke, and CorCa but not AoCa to be independently related to events. CONCLUSIONS: In summary, CorCa, but not AoCa, is related to cardiovascular events in patients with chest pain who undergo a cardiac-MDCT. CLINICAL RELEVANCE STATEMENT: We show that coronary artery calcification, but not aortic valve calcification, detected in a coronary CT scan is tightly related to cardiovascular events. Although this is a message already shown by other groups in the general population, we do believe that this work is unique because it is restricted to patients with chest pain sent to coronary CT. In other words, our work deals with what we face in our routine everyday practice. KEY POINTS: • The presence and the amount of coronary artery calcification are associated with cardiovascular events in patients with chest pain. • Aortic valve calcification is not associated with cardiovascular events in patients with chest pain.

Prognostic value of novel cardiovascular magnetic resonance transit times beyond the pulmonary circulation in patients with ventricular dysfunction.

OBJECTIVES: To evaluate the prognostic value of transit time (TT) assessment in the systemic circulation and organ perfusion in patients with ventricular dysfunction (VD). The primary endpoint was defined as death, heart failure admission, or ventricular arrhythmias, and the secondary endpoint was worsening renal function. METHODS: A retrospective study on 139 patients who underwent cardiac magnetic resonance for VD evaluation and 50 controls. TT was measured as peak-to-peak time in signal intensity over time curves obtained at different stages of circulation (right cavities, left cavities, aorta, and peripheral organs) from first-pass perfusion images. Outcomes were monitored over a median follow-up of 15 months. RESULTS: A total of 139 patients were included (84% male, age 63 [57-70] years). Patients exhibited significantly prolonged TT compared to controls, with in-patients showing longer times than outpatients. Among the 29 patients reaching the primary endpoint, both PTT and STT were significantly prolonged (PTT: 9.75 s vs 13.4 s, p < 0.01; STT: 4.77 s vs 7.00 s, p < 0.01). Concurrent prolongation of PTT (> 10 s) and STT (> 5 s) was associated with a higher event probability (42.3%), compared to isolated abnormalities (6.3% for PTT, 6.7% for STT). Multivariate analysis revealed that combined PTT and STT alteration independently predicted the combined endpoint (HR IC 95%: 8.685 (2.415-31.236), p = 0.001). Prolonged RPT was independently associated with renal function deterioration (OR IC 95%: 1.129 (1.015-1.256), p = 0.024). CONCLUSIONS: Evaluation of TT beyond pulmonary circulation provides prognostic insights into VD. Simultaneous assessment of PTT and STT enhances specificity compared to isolated PTT evaluation, predicting combined adverse events. RPT is independently associated with renal impairment. CLINICAL RELEVANCE STATEMENT: For the first time, it is described that transit time can be evaluated in systemic circulation and in peripheral organs and that this assessment can be easily made from conventional CMR perfusion images and holds significant prognostic value. KEY POINTS: Pulmonary transit time is a valuable hemodynamic parameter; systemic transit time may also be valuable. Transit time can be measured in the systemic circulation, and is longer in patients with ventricular dysfunction. Systemic transit time assessed by magnetic resonance imaging identifies patients with ventricular dysfunction who will experience events during follow-up.

Generative Pre-trained Transformer 4 analysis of cardiovascular magnetic resonance reports in suspected myocarditis: A multicenter study.

BACKGROUND: Diagnosing myocarditis relies on multimodal data, including cardiovascular magnetic resonance (CMR), clinical symptoms, and blood values. The correct interpretation and integration of CMR findings require radiological expertise and knowledge. We aimed to investigate the performance of Generative Pre-trained Transformer 4 (GPT-4), a large language model, for report-based medical decision-making in the context of cardiac MRI for suspected myocarditis. METHODS: This retrospective study includes CMR reports from 396 patients with suspected myocarditis and eight centers, respectively. CMR reports and patient data including blood values, age, and further clinical information were provided to GPT-4 and radiologists with 1 (resident 1), 2 (resident 2), and 4 years (resident 3) of experience in CMR and knowledge of the 2018 Lake Louise Criteria. The final impression of the report regarding the radiological assessment of whether myocarditis is present or not was not provided. The performance of Generative pre-trained transformer 4 (GPT-4) and the human readers were compared to a consensus reading (two board-certified radiologists with 8 and 10 years of experience in CMR). Sensitivity, specificity, and accuracy were calculated. RESULTS: GPT-4 yielded an accuracy of 83%, sensitivity of 90%, and specificity of 78%, which was comparable to the physician with 1 year of experience (R1: 86%, 90%, 84%, p = 0.14) and lower than that of more experienced physicians (R2: 89%, 86%, 91%, p = 0.007 and R3: 91%, 85%, 96%, p < 0.001). GPT-4 and human readers showed a higher diagnostic performance when results from T1- and T2-mapping sequences were part of the reports, for residents 1 and 3 with statistical significance (p = 0.004 and p = 0.02, respectively). CONCLUSION: GPT-4 yielded good accuracy for diagnosing myocarditis based on CMR reports in a large dataset from multiple centers and therefore holds the potential to serve as a diagnostic decision-supporting tool in this capacity, particularly for less experienced physicians. Further studies are required to explore the full potential and elucidate educational aspects of the integration of large language models in medical decision-making.

Bacteria Associated with Spores of Arbuscular Mycorrhizal Fungi Improve the Effectiveness of Fungal Inocula for Red Raspberry Biotization.

Intensive crop production leads to the disruption of the symbiosis between plants and their associated microorganisms, resulting in suboptimal plant productivity and lower yield quality. Therefore, it is necessary to improve existing methods and explore modern, environmentally friendly approaches to crop production. One of these methods is biotization, which involves the inoculation of plants with appropriately selected symbiotic microorganisms which play a beneficial role in plant adaptation to the environment. In this study, we tested the possibility of using a multi-microorganismal inoculum composed of arbuscular mycorrhizal fungi (AMF) and AMF spore-associated bacteria for biotization of the red raspberry. Bacteria were isolated from the spores of AMF, and their plant growth-promoting properties were tested. AMF inocula were supplemented with selected bacterial strains to investigate their effect on the growth and vitality of the raspberry. The investigations were carried out in the laboratory and on a semi-industrial scale in a polytunnel where commercial production of seedlings is carried out. In the semi-industrial experiment, we tested the growth parameters of plants and physiological response of the plant to temporary water shortage. We isolated over fifty strains of bacteria associated with spores of AMF. Only part of them showed plant growth-promoting properties, and six of these (belonging to the Paenibacillus genus) were used for the inoculum. AMF inoculation and co-inoculation of AMF and bacteria isolated from AMF spores improved plant growth and vitality in both experimental setups. Plant dry weight was improved by 70%, and selected chlorophyll fluorescence parameters (the contribution of light to primary photochemistry and fraction of reaction centre chlorophyll per chlorophyll of the antennae) were increased. The inoculum improved carbon assimilation, photosynthetic rate, stomatal conductance and transpiration after temporary water shortage. Raspberry biotization with AMF and bacteria associated with spores has potential applications in horticulture where ecological methods based on plant microorganism interaction are in demand.

Clinical characteristics and outcomes of aortic prosthetic valve endocarditis: comparison between transcatheter and surgical bioprostheses.

PURPOSE: Most data regarding infective endocarditis (IE) after transcatheter aortic valve implantation (TAVI) comes from TAVI registries, rather than IE dedicated cohorts. The objective of our study was to compare the clinical and microbiological profile, imaging features and outcomes of patients with IE after SAVR with a biological prosthetic valve (IE-SAVR) and IE after TAVI (IE-TAVI) from 6 centres with an Endocarditis Team (ET) and broad experience in IE. METHODS: Retrospective analysis of prospectively collected data. From the time of first TAVI implantation in each centre to March 2021, all consecutive patients admitted for IE-SAVR or IE-TAVI were prospectively enrolled. Follow-up was monitored during admission and at 12 months after discharge. RESULTS: 169 patients with IE-SAVR and 41 with IE-TAVI were analysed. Early episodes were more frequent among IE-TAVI. Clinical course during hospitalization was similar in both groups, except for a higher incidence of atrioventricular block in IE-SAVR. The most frequently causative microorganisms were S. epidermidis, Enterococcus spp. and S. aureus in both groups. Periannular complications were more frequent in IE-SAVR. Cardiac surgery was performed in 53.6% of IE-SAVR and 7.3% of IE-TAVI (p=0.001), despite up to 54.8% of IE-TAVI patients had an indication. No differences were observed about death during hospitalization (32.7% vs 35.0%), and at 1-year follow-up (41.8% vs 37.5%), regardless of whether the patient underwent surgery or not. CONCLUSION: Patients with IE-TAVI had a higher incidence of early prosthetic valve IE. Compared to IE-SAVR, IE-TAVI patients underwent cardiac surgery much less frequently, despite having surgical indications. However, in-hospital and 1-year mortality rate was similar between both groups.

Vibrationally Mode-Specific Molecular Energy Transfer to Surface Electrons in Metastable Formaldehyde Scattering from Cesium-Covered Au(111).

Nonadiabatic interaction of adsorbate nuclear motion with the continuum of electronic states is known to affect the dynamics of chemical reactions at metal surfaces. A large body of work has probed the fundamental mechanisms of such interactions for atomic and diatomic molecules at surfaces. In polyatomic molecules, the possibility of mode-specific damping of vibrational motion due to the effects of electronic friction raises the question of whether such interactions could profoundly affect the outcome of chemistry at surfaces by selectively removing energy from a particular intramolecular adsorbate mode. However, to date, there have not been any fundamental experiments demonstrating nonadiabatic electron-vibration coupling in a polyatomic molecule at a surface. In this work, we scatter excited metastable formaldehyde and formaldehyde-d2 from a low work function surface and detect ejected exoelectrons that accompany molecular relaxation. The exoelectron ejection efficiency exhibits a strong dependence on the vibrational mode that is excited: out-of-plane bending excitation (ν4) leads to significantly more exoelectrons than does CO stretching excitation (ν2). The results provide clear evidence for mode-specific energy transfer from vibration to surface electrons.

Mitochondrial double-stranded RNA triggers antiviral signalling in humans.

Mitochondria are descendants of endosymbiotic bacteria and retain essential prokaryotic features such as a compact circular genome. Consequently, in mammals, mitochondrial DNA is subjected to bidirectional transcription that generates overlapping transcripts, which are capable of forming long double-stranded RNA structures1,2. However, to our knowledge, mitochondrial double-stranded RNA has not been previously characterized in vivo. Here we describe the presence of a highly unstable native mitochondrial double-stranded RNA species at single-cell level and identify key roles for the degradosome components mitochondrial RNA helicase SUV3 and polynucleotide phosphorylase PNPase in restricting the levels of mitochondrial double-stranded RNA. Loss of either enzyme results in massive accumulation of mitochondrial double-stranded RNA that escapes into the cytoplasm in a PNPase-dependent manner. This process engages an MDA5-driven antiviral signalling pathway that triggers a type I interferon response. Consistent with these data, patients carrying hypomorphic mutations in the gene PNPT1, which encodes PNPase, display mitochondrial double-stranded RNA accumulation coupled with upregulation of interferon-stimulated genes and other markers of immune activation. The localization of PNPase to the mitochondrial inter-membrane space and matrix suggests that it has a dual role in preventing the formation and release of mitochondrial double-stranded RNA into the cytoplasm. This in turn prevents the activation of potent innate immune defence mechanisms that have evolved to protect vertebrates against microbial and viral attack.

In vitro reconstitution reveals a key role of human mitochondrial EXOG in RNA primer processing.

The removal of RNA primers is essential for mitochondrial DNA (mtDNA) replication. Several nucleases have been implicated in RNA primer removal in human mitochondria, however, no conclusive mechanism has been elucidated. Here, we reconstituted minimal in vitro system capable of processing RNA primers into ligatable DNA ends. We show that human 5'-3' exonuclease, EXOG, plays a fundamental role in removal of the RNA primer. EXOG cleaves short and long RNA-containing flaps but also in cooperation with RNase H1, processes non-flap RNA-containing intermediates. Our data indicate that the enzymatic activity of both enzymes is necessary to process non-flap RNA-containing intermediates and that regardless of the pathway, EXOG-mediated RNA cleavage is necessary prior to ligation by DNA Ligase III. We also show that upregulation of EXOG levels in mitochondria increases ligation efficiency of RNA-containing substrates and discover physical interactions, both in vitro and in cellulo, between RNase H1 and EXOG, Pol γA, Pol γB and Lig III but not FEN1, which we demonstrate to be absent from mitochondria of human lung epithelial cells. Together, using human mtDNA replication enzymes, we reconstitute for the first time RNA primer removal reaction and propose a novel model for RNA primer processing in human mitochondria.

THAP1 modulates oligodendrocyte maturation by regulating ECM degradation in lysosomes.

Mechanisms controlling myelination during central nervous system (CNS) maturation play a pivotal role in the development and refinement of CNS circuits. The transcription factor THAP1 is essential for timing the inception of myelination during CNS maturation through a cell-autonomous role in the oligodendrocyte lineage. Here, we demonstrate that THAP1 modulates the extracellular matrix (ECM) composition by regulating glycosaminoglycan (GAG) catabolism within oligodendrocyte progenitor cells (OPCs). Thap1-/- OPCs accumulate and secrete excess GAGs, inhibiting their maturation through an autoinhibitory mechanism. THAP1 controls GAG metabolism by binding to and regulating the GusB gene encoding ß-glucuronidase, a GAG-catabolic lysosomal enzyme. Applying GAG-degrading enzymes or overexpressing ß-glucuronidase rescues Thap1-/- OL maturation deficits in vitro and in vivo. Our studies establish lysosomal GAG catabolism within OPCs as a critical mechanism regulating oligodendrocyte development.