Biology subjects

Molnar, E.

Publications and source records attributed to Molnar, E..

9 recordsLinked to original sources

bioRxiv2026

Flow-Induced Yap/Taz Signaling Balances Endothelial and Hematopoietic Stem Cell Fates

Mechanical forces from blood flow are essential for production of hematopoietic stem and progenitor cells (HSPCs) during embryogenesis, but the molecular mechanisms by which hemodynamic cues are sensed and orchestrate endothelial-to-hematopoietic (EHT) transition remain incompletely defined. We previously identified YAP mechanotransduction as a key integrator of physical forces with EHT. Here we show that hemodynamic forces can activate YAP signaling via the mechanoresponsive ion channel Piezo1 in human iPSC-derived hemogenic endothelium (HE) and zebrafish embryos. Investigation of the Piezo1/YAP axis revealed shared and unique roles of YAP and its paralogue TAZ in EHT. Mechanistically, we find a requirement for the Tead DNA-binding co-factor in YAP/TAZ-dependent control of HSPC number, and note that TAZ uniquely augments transcriptional output of the hematopoietic master regulator Runx1 via direct protein-protein interactions. By comprehensive scRNA-sequencing of YAP/TAZ gain-of-function (GOF) and yap-deficient cells from zebrafish, we reveal that YAP/TAZ promotes HSC production by positively regulating gene programs for hematopoietic self-renewal, cell cycle, and glycolysis-to-oxidative phosphorylation switching, while preventing reversion to endothelial identity. Importantly, comparison of GOF transcriptomes and functional analyses suggest decoupling of metabolic/proliferative and endothelial gene regulatory modules between YAP and TAZ: while either can functionally compensate for loss of the other in EHT, indiscriminate overactivation of TAZ enhances an endothelial program over pro-hematopoietic fate, ultimately blunting progression of HSPC production. Given that hemodynamic cues are integrated simultaneously by arterial and HE cells in embryonic vessels in which EHT occurs, these findings have strong implications for strategies designed to introduce biomechanical cues to in vitro hematopoietic differentiation systems to drive HSC production.

Cell Biology↗

bioRxiv2026

Complex regulation of RETINOBLASTOMA-RELATED's interactions with E2Fs via phosphorylation

Arabidopsis RETINOBLASTOMA-RELATED (RBR) regulates cell proliferation by interacting with E2F transcription factors and DIMERIZATION PARTNER, RB-LIKE, E2F AND MULTI-VULVAL CLASS B COMPLEX (DREAM) components. Although CDK-CYCD phosphorylation is believed to affect RBRs E2F-binding capacity, the precise phosphorylation events inhibiting RBRs cell cycle function remain unclear. This study found RBR phosphorylated at 13 of 16 CDK sites in Arabidopsis, with many phosphorylated forms still binding E2Fs. In contrast, multi-phosphorylated RBR forms with phosphorylated 911S site in Arabidopsis thaliana and corresponding sites in Medicago truncatula or Brassica napus do not co-purify with E2Fs and DREAM components but interact with RNA-binding proteins involved in post-transcriptional regulation through ribosomal biogenesis and protein translation. The 911S phosphorylation is high in proliferating cells and rapidly diminishes under DNA damage conditions, indicating its role in switching from proliferation to quiescence under stress. However, molecular modelling implies that this site is not accessible for phosphorylation if RBR is in complex with E2Fs. These findings suggest that different phosphorylation events inhibit RBRs capacity to form complexes with E2Fs and to release E2Fs from RBR inhibition. We posit that multi-site phosphorylation coupled to 911S impedes free RBRs binding to E2Fs and DREAM components, but this is not the initial inhibitory phosphorylation contributing to the disruption of RBR-E2F-DP complexes. Rather, it facilitates RBR interaction with proteins involved in post-transcriptional cell cycle regulation.

plant biology↗

bioRxiv2024

Retinoblastoma-related (RBR) has both canonical and non-canonical regulatory functions during thermo-morphogenic responses in Arabidopsis seedlings

Warm temperatures accelerate plant growth, but the underlying molecular mechanism is not fully understood. Here, we show that increasing the temperature from 22{degrees}C to 28{degrees}C rapidly activates proliferation in the apical shoot and root meristems of wild-type Arabidopsis seedlings. We found that one of the central regulators of cell proliferation, the cell cycle inhibitor RETINOBLASTOMA-RELATED (RBR), is suppressed by warm temperatures. RBR became hyper-phosphorylated at a conserved CYCLIN-DEPENDENT KINASE (CDK) site in young seedlings growing at 28{degrees}C, in parallel with the stimulation of the expressions of the regulatory CYCLIN D/A subunits of CDK(s). Interestingly, while under warm temperatures ectopic RBR slowed down the acceleration of cell proliferation, it triggered elongation growth of post-mitotic cells in the hypocotyl. In agreement, the central regulatory genes of thermomorphogenic response, including PIF4 and PIF7, as well as their downstream auxin biosynthetic YUCCA genes (YUC1-2 and YUC8-9) were all up-regulated in the ectopic RBR expressing line but down-regulated in a mutant line with reduced RBR level. We suggest that RBR has both canonical and non-canonical functions under warm temperatures to control proliferative and elongation growth, respectively.

plant biology↗

bioRxiv2024

Dominant suppressor genes of p53-induced apoptosis in Drosophila melanogaster

Apoptosis, the programmed cell death, is responsible for the removal of cells seriously damaged or unwanted in development. A major function of apoptosis is the removal of cells which suffered oncogenic mutations, thereby preventing cancerous transformation. By making use of the DEP transposon, a P element derivative made in our laboratory, we made an insertional mutagenesis screen in Drosophila melanogaster to identify genes which, when overexpressed, suppress the p53-activated apoptosis. The DEP element has Gal4-activatable, outward-directed UAS-promoters at both ends which can be deleted separately in vivo. In the DEP insertion mutants, we used the GMR-Gal4 driver to induce transcription from both UAS-promoters and tested the suppression effect on the apoptotic rough eye phenotype generated by an activated UAS-p53 transgene. By DEP insertions, seven genes were identified which suppressed the p53-induced apoptosis. In four mutants, the suppression effect was resulted by single genes activated by one UAS-promoter (Pka-R2, Rga, crol, Spt5). In the other three (Orct2, Polr2M, stg), deleting either UAS-promoter eliminated the suppression effect. In qPCR experiments we found that the genes in the vicinity of the DEP insertion also showed an elevated expression level. This suggested an additive effect of the nearby genes on suppressing apoptosis. In the eucaryotic genomes there are co-expressed gene clusters. Three of the DEP insertion mutants are included and two are in close vicinity of separate co-expressed gene clusters. This raises the possibility that the activity of some of the genes in these clusters may help the suppression of the apoptotic cell death.

genetics↗

bioRxiv2022

The canonical E2Fs together with RETINOBLASTOMA-RELATED are required to establish quiescence during plant development

Maintaining stable and transient quiescence in differentiated and stem cells, respectively, requires repression of the cell cycle. The plant RETINOBLASTOMA-RELATED (RBR) has been implicated in stem cell maintenance, presumably by forming repressor complexes with E2F transcription factors. Surprisingly we find that mutations in all three canonical E2Fs do not compromise the cell cycle, but similarly to RBR silencing, result in overproliferation. Contrary to the growth arrest upon RBR silencing, when exit from proliferation to differentiation is inhibited, the e2fabc mutant develops enlarged organs with supernumerary stem and differentiated cells as the quiescence is compromised. While E2F, RBR and the M-phase regulatory MYB3Rs are part of the DREAM repressor complexes, and recruited to overlapping groups of targets, they regulate distinct sets of genes. Only the loss of E2Fs but not the MYB3Rs interferes with quiescence, which might be due to the ability of E2Fs to control both G1-S and some key G2-M targets. We conclude that collectively the three canonical E2Fs in complex with RBR have central roles in establishing cellular quiescence during organ development, leading to enhanced plant growth.

plant biology↗

bioRxiv2019

Y-chromosome haplogroups from Hun, Avar and conquering Hungarian period nomadic people of the Carpathian Basin

Hun, Avar and conquering Hungarian nomadic groups arrived into the Carpathian Basin from the Eurasian Steppes and significantly influenced its political and ethnical landscape. In order to shed light on the genetic affinity of above groups we have determined Y chromosomal haplogroups and autosomal loci, from 49 individuals, supposed to represent military leaders. Haplogroups from the Hun-age are consistent with Xiongnu ancestry of European Huns. Most of the Avar-age individuals carry east Eurasian Y haplogroups typical for modern north-eastern Siberian and Buryat populations and their autosomal loci indicate mostly unmixed Asian characteristics. In contrast the conquering Hungarians seem to be a recently assembled population incorporating pure European, Asian and admixed components. Their heterogeneous paternal and maternal lineages indicate similar phylogeographic origin of males and females, derived from Central-Inner Asian and European Pontic Steppe sources. Composition of conquering Hungarian paternal lineages is very similar to that of Baskhirs, supporting historical sources that report identity of the two groups.

genetics↗

bioRxiv2018

Inner Asian maternal genetic origin of the Avar period nomadic elite in the 7th century AD Carpathian Basin

After 568 AD the nomadic Avars settled in the Carpathian Basin and founded their empire, which was an important force in Central Europe until the beginning of the 9th century AD. The Avar elite was probably of Inner Asian origin; its identification with the Rourans (who ruled the region of todays Mongolia and North China in the 4th-6th centuries AD) is widely accepted in the historical research.\n\nHere, we study the whole mitochondrial genomes of twenty-three 7th century and two 8th century AD individuals from a well-characterised Avar elite group of burials excavated in Hungary. Most of them were buried with high value prestige artefacts and their skulls showed Mongoloid morphological traits.\n\nThe majority (64%) of the studied samples mitochondrial DNA variability belongs to Asian haplogroups (C, D, F, M, R, Y and Z). This Avar elite group shows affinities to several ancient and modern Inner Asian populations.\n\nThe genetic results verify the historical thesis on the Inner Asian origin of the Avar elite, as not only a military retinue consisting of armed men, but an endogamous group of families migrated. This correlates well with records on historical nomadic societies where maternal lineages were as important as paternal descent.

genomics↗

bioRxiv2017

Parallel ancient genomic transects reveal complex population history of early European farmers

Ancient DNA studies have established that European Neolithic populations were descended from Anatolian migrants who received a limited amount of admixture from resident hunter-gatherers. Many open questions remain, however, about the spatial and temporal dynamics of population interactions and admixture during the Neolithic period. Using the highest-resolution genome-wide ancient DNA data set assembled to date--a total of 177 samples, 127 newly reported here, from the Neolithic and Chalcolithic of Hungary (6000-2900 BCE, n = 98), Germany (5500-3000 BCE, n = 42), and Spain (5500-2200 BCE, n = 37)--we investigate the population dynamics of Neolithization across Europe. We find that genetic diversity was shaped predominantly by local processes, with varied sources and proportions of hunter-gatherer ances try among the three regions and through time. Admixture between groups with different ancestry profiles was pervasive and resulted in observable population transformation across almost all cultural transitions. Our results shed new light on the ways that gene flow reshaped European populations throughout the Neolithic period and demonstrate the potential of time-series-based sampling and modeling approaches to elucidate multiple dimensions of historical population interactions.

genetics↗

bioRxiv2016

Revising mtDNA haplotypes of the ancient Hungarian conquerors with next generation sequencing

As part of the effort to create a high resolution representative sequence database of the medieval Hungarian conquerors we have resequenced the entire mtDNA genome of 24 published ancient samples with Next Generation Sequencing, whose haplotypes had been previously determined with traditional PCR based methods. We show that PCR based methods are prone to erroneous haplotype or haplogroup determination due to ambiguous sequence reads, and many of the resequenced samples had been classified inaccurately. The SNaPshot method applied with published ancient DNA authenticity criteria is the most straightforward and cheapest PCR based approach for testing a large number of coding region SNP-s, which greatly facilitates correct haplogroup determination.

genetics↗