Biology subjects

Cerny, J.

Publications and source records attributed to Cerny, J..

5 recordsLinked to original sources

bioRxiv2025

Disruption of grin2A, an epilepsy-associated gene, produces altered spontaneous swim behavior in zebrafish

N-methyl-D-aspartate receptors (NMDARs) control synaptic plasticity and brain development in a manner determined by receptor subunit composition. Pathogenic variants in GRIN2A gene, encoding the NMDAR GluN2A subunit, can cause gain or loss of function of receptors containing the affected subunit, and are associated with intellectual disability and epilepsy in patients. While in-vitro studies of recombinant receptors have yielded some insights, animal experimental models are essential to better understand the relationship between the molecular pathology of the variants and the disease. Here we introduce a zebrafish model of GluN2A loss of function to study system-level effects of zebrafish grin2Aa and grin2Ab gene deletion. Our electrophysiological analysis revealed functional differences between receptors containing zebrafish GluN2Aa/b and GluN2Bb paralogs comparable to mammalian receptors containing GluN2A vs. GluN2B subunits. Both grin2Aa-/- and grin2Ab-/-, as well as double-knockout grin2A-/- zebrafish larvae showed increased locomotor activity in a novel environment. Proteomic analysis suggested that the relative proportion of GluN2B-containing NMDARs may be increased in grin2A mutant fish. Our results highlight fundamental similarities between zebrafish and mammalian NMDAR signaling and validate the use of zebrafish as a model organism to study the neurodevelopmental role of NMDARs. The newly created transgenic zebrafish strains complement the rodent models of GluN2A loss of function and can be used for high-throughput testing of pharmacological or genetic treatment strategies for patients with GRIN2A gene variants.

neuroscience↗

bioRxiv2025

Claudin 1-mediated positioning of DC1 to mTECs is essential for antigen transfer-coupled DC1 maturation and maintenance of central tolerance

The mechanisms of central tolerance, which rely on the presentation of self-antigens by medullary thymic epithelial cells (mTECs) and DCs, prevent autoimmunity by eliminating self-reactive T-cells. While mTECs produce self-antigens in an autonomous manner, DCs acquire them from mTECs via cooperative antigen transfer (CAT). Our recent data showed that preferential pairing occurs between distinct subsets of mTECs and DCs in CAT, providing a rationale for the existence of molecular determinants which control such pairing and the outcome of central tolerance. Here, we compared the transcriptomes of CAT-experienced and -inexperienced DCs and identified Claudin 1 as a molecule involved in CAT-coupled type 1 DC (DC1) maturation. By mapping thymic DC1 heterogeneity, we identified their early and late maturation states. DC1-specific ablation of Claudin 1 led to a reduction in CAT-experienced late mature DC1s and hampered DC1 maturation. These phenotypes correlated with the displacement of DC1s from the vicinity of mTECs. This translated into impaired Treg selection and clonal deletion of TRA-specific T-cells manifested via a break in tolerance and symptoms of multi-organ autoimmunity. Collectively, our results identify thymic DC1-derived Claudin 1 as a regulator of immune tolerance. One Sentence SummaryThe expression of Claudin 1 on type 1 dendritic cells regulates their proximity to mTECs, which is required for effective antigen transfer coupled with DC1 maturation and establishment of T-cell tolerance.

immunology↗

bioRxiv2024

Light-dependent flavin redox and adduct states control the conformation and DNA binding activity of the transcription factor EL222

The activity of the transcription factor EL222 is regulated through protein-chromophore adduct formation, interdomain dynamics, oligomerization and protein-DNA interactions, all triggered by photo-excitation of its flavin mononucleotide (FMN) cofactor. To gain molecular-level insight into the photocycle of EL222, we applied complementary methods: macromolecular X-ray crystallography (MX), nuclear magnetic resonance (NMR) spectroscopy, optical spectroscopies (infrared and UV/visible), molecular dynamics/metadynamics (MD/metaD) simulations, and protein engineering using non-canonical amino acids. The observation of only subtle atomic displacements between crystal structures of EL222 with and without blue-light back-illumination, was confirmed by NMR data indicating no major changes in secondary structure and fold compactness. Kinetic experiments in solution provided evidence for two distinct EL222 conformations (lit1 and lit2) that become sequentially populated under illumination. These two lit states were assigned to covalently-bound N5 protonated, and non-covalently-bound hydroquinone forms of FMN, respectively. Molecular modeling revealed differential dynamics and domain separation times arising from the three FMN states (oxidized, adduct, and reduced). Furthermore, while the dark state is largely monomeric, both lit states undergo slow monomer-dimer exchange. The photoinduced loss of -helicity, seen by infrared difference spectroscopy, was ascribed to dimeric EL222 species. Unexpectedly, NMR revealed that all three EL222 species (dark, lit1, lit2) can associate with DNA to some extent, but only under illumination a high population of stable complexes is obtained. Overall, we propose a refined model of EL222 photo-activation where photoinduced changes in the oxidation state of FMN and thioadduct formation shift the population equilibrium towards an open conformation that favors self-association and DNA-binding. Significance StatementFlavin-binding light-oxygen-voltage (LOV) proteins constitute a prominent example of highly evolved chromophore-containing proteins that convert light into biochemical changes in the cell. However, it is not well understood how blue-light orchestrates changes in LOV structure and function. Here we show that the dynamics, oligomerization and DNA-binding properties of the photocontrolled transcription factor EL222 are dependent on both the flavin redox state and thioadduct formation. In the dark, monomeric EL222 forms transient encounter complexes with DNA. Under illumination, two distinct lit states are sequentially generated, termed lit1 and lit2, that are both able to assemble into EL222:DNA (2:1) complexes. Our results reveal the coupling between flavin photochemistry (protonation and covalent linkage) and fold stability in EL222 and potentially other flavoproteins.

biochemistry↗

bioRxiv2024

Protamine 2 Deficiency Results In Septin 12 Abnormalities

There is a well-established link between abnormal sperm chromatin states and poor motility, however, how these two processes are interdependent is unknown. Here, we identified a possible mechanistic insight by showing that Protamine 2, a nuclear DNA packaging protein in sperm, directly interacts with cytoskeletal protein Septin 12, which is associated with sperm motility. Septin 12 has several isoforms, and we show, that in the Prm2-/-sperm, the short one (Mw 36 kDa) is mislocalized, while two long isoforms (Mw 40 and 41 kDa) are unexpectedly lost in Prm2-/- sperm chromatin-bound protein fractions. Septin 12 co-immunoprecipitated with Protamine 2 in the testicular cell lysate of WT mice and with Lamin B1/B2/B3 in co-transfected HEK cells despite we did not observe changes in Lamin B2/B3 protein or SUN4 expression in Prm2-/-testes. Furthermore, the Prm2-/- sperm have on average a smaller sperm nucleus and aberrant acrosome biogenesis. In humans, patients with low sperm motility (asthenozoospermia) have imbalanced histone- protamine 1/2 ratio and modified levels of cytoskeletal proteins. We detected retained Septin 12 isoforms (Mw 40 and 41 kDa) in the sperm membrane, chromatin-bound and tubulin/mitochondria protein fractions, which was not true for healthy normozoospermic men. In conclusion, our findings expand the current knowledge regarding the connection between Protamine 2 and Septin 12 expression and localization, resulting in low sperm motility and morphological abnormalities.

cell biology↗

bioRxiv2022

Mapping the potential distribution of the principal vector of Crimean-Congo hemorrhagic fever virus Hyalomma marginatum in Europe

Crimean-Congo haemorrhagic fever (CCHF) is the most widely distributed tick-borne viral disease in humans. The virus is widely expanded across western China, South Asia, and the Middle East to southeastern Europe and Africa. Its causative agent, Crimean-Congo haemorrhagic fever virus (CCHFV), is among the deadliest human pathogens in Africa and Eurasia. The historical known distribution of the CCHFV vector Hyalomma marginatum in Europe included most of the Mediterranean and the Balkan countries, Ukraine, and southern Russia. Further expansion of its potential distribution is possibly occurred in and out of the Mediterranean region. This study updated the map of the principal vector of CCHFV, H. marginatum, in the Old World. The model estimated the environmental suitability of H. marginatum in the Old World, including Europe. On the continental European scale, the model anticipated a widespread potential distribution, covering southern, western, central, and eastern Europe, as far north as southern parts of Scandinavian countries. The distribution of H. marginatum also covered the countries across the central part of Europe where the species is not autochthonous. All models were statistically robust and performed better than random (p < 0.001). Based on the results of the model, climatic conditions could hamper the successful overwintering of H. marginatum and their survival as adults in many areas of the region. Regular updates of the models, using updated occurrence, current, and future climatic data are recommended to regularly assess the areas at risk. SummaryHyalomma marginatum is a vector of numerous highly important human and animal pathogens. It is the main vector of Crimean-Congo haemorrhagic fever virus (CCHFV) in Europe. This study updated the potential distribution of H. marginatum on a global scale, including Europe, with a particular focus on Central Europe. The model predicted a widespread potential distribution of H. marginatum on the continental European scale, anticipating occurrences of H. marginatum in southern, western, central, and eastern Europe, as far north as southern parts of Scandinavian countries. In Central Europe, H. marginatum populations have not been established in any of the countries yet, but the presence of the species has been reported from all countries in the region. Their potential spread northwards and establishment of permanent populations of H. marginatum in the north are therefore of great importance, in particular since the immature stages of H. marginatum are frequently found on migratory birds flying northwards to temperate Europe. Our ecological niche model of H. marginatum in Central Europe anticipated its distribution in all countries of the region. Our prediction for current global potential distribution of this tick species can help in understanding disease risk areas associated with this vector.

ecology↗