Biology subjects

Leitner, M.

Publications and source records attributed to Leitner, M..

5 recordsLinked to original sources

bioRxiv2026

Single-cell analysis of West Nile virus infection in brain organoids identified a serine synthesis enzyme as a determinant of viral neural tropism and a druggable antiviral target

The cellular and molecular determinants of human neuroinvasive West Nile virus (WNV) disease are currently poorly defined. Previous studies of WNV neural infection relied on rodent models and immortalised cell lines that diverge from human brain tissue. Herein, we established a reproducible human cerebral organoid model of WNV infection and profiled it by virus-inclusive single-cell RNA sequencing (scRNA-Seq) to obtain an understanding of WNV-host interactions in the context of human neural tissue. We found that WNV showed preferential tropism to progenitor cells, immature neurons, and astrocytes, while the mature neurons were largely resistant to infection. Astrocytes were identified as the principal source of interferon (IFN) and the main hub of IFN-signalling, whereas mature neurons expressed little viral RNA-sensing machinery or STAT1 and responded weakly to infection and to IFN. The differential gene expression analysis between WNV-permissive and nonpermissive cells demonstrated that virus-susceptible cells had high baseline expression of the serine synthesis and one-carbon metabolism genes PHGDH, SHMT2, and MTHFD2, which were not induced by infection. RNA-interference and pharmacological inhibition of phosphoglycerate dehydrogenase (PHGDH) restricted WNV replication, confirming the requirement of this gene for WNV infection. In addition, the FDA-approved drug disulfiram, known to inhibit PHGDH, also reduced viral replication in neural progenitors and cerebral organoids. Overall, these results provide the first comprehensive single-cell-level characterisation of WNV neural infection in human neural tissue. They identify de novo serine synthesis as a metabolic dependency of WNV in human neural cells that can be targeted as a host-directed antiviral therapy.

microbiology↗

bioRxiv2026

AI-enhanced cardiac digital twins extend drug proarrhythmic risk assessment through experimental data uncertainty propagation and overdose exploration: a loperamide case study

Drug-induced QT interval prolongation is a key biomarker of proarrhythmic risk and central to drug cardiac safety evaluation alongside in vitro assays and animal studies. Current preclinical frameworks, however, provide limited insight into how experimental uncertainty and extreme exposures translate into real-world arrhythmic risk, despite both factors critically modulating outcomes. To address this, we used sex-specific machine learning surrogate models trained on 3D cardiac digital twins--mechanistic electrophysiology models of anatomically detailed ventricles that integrate multichannel ion-channel block data. These emulators combine the realism of 3D simulations with high-throughput capability, enabling rapid, ethically unconstrained assessment of proarrhythmic risk. We illustrate the approach using loperamide, safe at therapeutic doses but linked to fatal arrhythmias at extreme exposures. Two analyses were performed: propagating experimental IC50 and Hill coefficient variability to quantify its effect on predicted QT prolongation and arrhythmic probability, and simulating extreme exposures to identify sex-specific arrhythmogenic thresholds. Experimental variability substantially broadened predicted QT prolongation and arrhythmic risk near decision thresholds. Extreme exposure simulations identified arrhythmogenic thresholds of approximately 107-109 x Cmax in female models and 213-286 x Cmax in male models. This framework offers a scalable, physics-based tool for early-stage drug cardiac safety evaluation.

bioengineering↗

bioRxiv2025

Ashwin and FAM98 paralogs define nuclear and cytoplasmic RNA ligase complexes for tRNA biogenesis and the unfolded protein response

The tRNA ligase complex (tRNA-LC) seals tRNA exon halves in the nucleus after the removal of a single intron, and joins XBP1-mRNA exons in the cytoplasm as part of the unfolded protein response (UPR). This dual function requires simultaneous nuclear and cytoplasmic localization. Here, we reveal that Ashwin (ASW), the vertebrate-specific subunit of the tRNA-LC, serves as its nuclear import factor. ASW displays a dual nuclear localisation signal (NLS) which, upon disruption, leads to the retention of the tRNA-LC in the cytoplasm with a consequent impairment of pre-tRNA splicing and accumulation of 5 tRNA fragments. We also show that the tRNA-LC exists in three forms depending on which FAM98 paralog is chosen, either FAM98A, FAM98B or FAM98C. We find that ASW interacts exclusively with the FAM98B-containing complex, allowing its nuclear localization for tRNA biogenesis. Attaching an NLS to RTCB, the catalytic and indispensable subunit, rescues pre-tRNA splicing in cells depleted of ASW. We envision that vertebrates evolved ASW to localize a sub-population of tRNA-LC to the nucleus, while using FAM98 paralogs to retain a fraction of RTCB in the cytoplasm for XBP1-mRNA splicing during UPR.

cell biology↗

bioRxiv2025

Structural framework for the assembly of the human tRNA ligase complex

In human cells, a subset of tRNA-encoding genes contain introns. These are removed by a non-canonical splicing pathway in which the tRNA splicing endonuclease complex catalyzes intron excision and the resulting exons are subsequently ligated by the tRNA-ligase complex (tRNA-LC). Although recent studies have provided insights into the process of intron removal, the molecular mechanisms underpinning tRNA ligation by tRNA-LC remain elusive. The tRNA-LC is a hetero-pentameric protein assembly consisting of Ashwin, CGI-99, FAM98B, the DEAD-box helicase DDX1 and the catalytic subunit RTCB/HSPC117. Using cryo-EM, we have determined an atomic-resolution reconstruction of human tRNA-LC. We find that CGI-99, DDX1 and FAM98B form an alpha-helical bundle that contacts RTCB via an interface located on the opposite side from the location of the ligase active site and tethers DDX1 to the tRNA-LC via its C-terminal helix. FAM98B and CGI-99 extensively interact in an intricately co-folded heterodimer that clamps Ashwin in a pincer-like structure. Interaction analysis using structure-based mutants of tRNA-LC subunits supports the overall architecture of the complex. Finally, we show that the paralogous proteins FAM98A and FAM98C underpin the assembly of compositionally distinct RTCB-containing complexes that lack Ashwin and may have distinct cellular functions. Together, our results provide new insights into the assembly and mechanism of the tRNA ligase complex, shedding light on its functions in tRNA biogenesis and beyond.

biochemistry↗

bioRxiv2020

Pediatric glioblastoma - unlike normal cells - are sensitive to the combination of vorinostat and olaparib and to its downstream effector - phosphorylated eIF2α

Current therapies offer only a short relief for patients with pediatric glioblastoma (PED-GBM). Therefore, expanding treatment options for this fatal disease is of utmost importance. We found that PED-GBM cell lines, originated from diffuse intrinsic pontine glioma expressing H3K27M mutation (DIPG), or from hemispheric glioma expressing H3G34R mutation, are sensitive to combinations of histone deacetylase and PARP-1 inhibitors (vorinostat with either olaparib or veliparib). These combinations led to an enhanced decrease in their survival, and to increased phosphorylation of eIF2. Experiments with the S51D phosphomimetic variant of eIF2 and with brain-penetrating inhibitors of phosphorylated eIF2 (p-eIF2) dephospohrylation, salubrinal and raphin1, showed that increased eIF2 phosphorylation diminished PED-GBM cell survival and sensitized them to PARP-1 inhibitors as well as to ionizing irradiation, which is the main treatment modality in these patients. PED-GBM cells were also remarkably more sensitive to combination of vorinostat and PARP-1 inhibitors and to salubrinal and raphin1 than normal human astrocytes and fibroblasts. Importantly, although the overall effect of increased eIF2 phosphorylation was a reduced survival of PED-GBM cells, it also increased the cellular level of MTH1, an enzyme that protects treated cells against the incorporation of oxidized nucleotides into nucleic acids, resulting in an enhanced decrease in cell survival in response to the combination of salubrinal and MTH1 inhibitor, TH588. Our results indicate that combinations of the FDA approved drugs, vorinostat and either veliparib or olaparib, could potentially be included in PED-GBM treatment protocols and that the effect of salubrinal and raphin1 on PED-GBM survival warrants further evaluation.

cancer biology↗