Biology subjects

Jauch, A.

Publications and source records attributed to Jauch, A..

12 recordsLinked to original sources

bioRxiv2025

Long-term prevention of aneuploidy in human pluripotent stem cells by fine-tuning GSK3 activity

Human pluripotent stem cells (hPSCs) are critical cell sources to model human development and hold promise towards regenerative medicine. However, cultured hPSCs quickly acquire chromosome gains or losses (aneuploidy) due to high replicative stress and errors in chromosome segregation, which hampers their use for stem cell therapies. We have recently described that embryo patterning signals control chromosome segregation fidelity during early human lineage specification by modulating the response to replicative stress. Here, we demonstrate that fine-tuned activation of WNT signalling using off-the-shelf GSK3 inhibitors prevents chromosome missegregation and aneuploidy during long term passaging of hPSCs. Lineage-specification and sequencing analyses demonstrate that hPSCs culture with E8 supplemented with a low dosage of GSK3 inhibitors retain primed pluripotency and full potential to the differentiation into the 3 germ layers for over 30 passages. Strikingly, detailed mitotic studies revealed that long-term cultured hPSCs often display ultra-fine chromosome bridges during anaphase due to unreplicated DNA, which can result in hitherto uncharacterised copy-number-variations and other genomic aberrations. We show that culture with low dosage of the GSK3 inhibitor CHIR99021, but not direct attenuation of DNA replication stress using nucleosides, prevents mitotic DNA synthesis and the formation of ultra-fine bridges during long term hPSC passage. Taken together, we propose to enrich E8 culture media with 100 nM CHIR99021 to maintain euploidy in primed hPSCs, and to routinely map for genomic alterations, in addition to aneuploidy, for modelling and regenerative medicine studies.

cell biology↗

bioRxiv2024

Lifespan trajectory of chimpanzee brains characterized by magnetic resonance imaging histology

Chimpanzee brain maturation provides an invaluable framework for understanding the evolution of the human brain. We performed ultra-high resolution quantitative magnetic resonance imaging (qMRI) with histological validation on post mortem brains from captive and wild chimpanzees with a broad age range. We mapped developmental myelination and age-related iron accumulation across regions and layers of the neocortex. Compared to humans, chimpanzees showed more myelination and iron deposition in motor and premotor cortices, while the auditory cortex was more strongly myelinated in humans. Our model suggests that chimpanzees cortical myelination was largely completed by the age of nine years, while iron accumulation continued throughout the lifespan. The regions with highest adult levels of myelin and iron took the longest to mature, challenging the widespread assumption that highly myelinated regions complete their development first. The reported maps and developmental curves provide a foundation for comparative neuroscience research and understanding of human brain evolution.

neuroscience↗

bioRxiv2023

STIL overexpression shortens lifespan and reduces tumor formation in mice

Centrosomes are the major microtubule organizing centers of animal cells. Supernumerary centrosomes are a common feature of human tumors and associated with karyotype abnormalities and aggressive disease, but whether they are cause or consequence of cancer remains controversial. Here, we analyzed the consequences of centrosome amplification by generating transgenic mice in which centrosome numbers can be increased by overexpression of the structural centrosome protein STIL. We show that STIL overexpression induces centrosome amplification and aneuploidy, leading to senescence, apoptosis, and impaired proliferation in mouse embryonic fibroblasts, and microcephaly with increased perinatal lethality and shortened lifespan in mice. Importantly, both overall tumor formation in mice with constitutive, global STIL overexpression and chemical skin carcinogenesis in animals with inducible, skin-specific STIL overexpression were reduced, an effect that was not rescued by concomitant p53 inactivation. These results suggest that supernumerary centrosomes impair proliferation in vitro as well as in vivo, resulting in reduced lifespan and spontaneous as well as carcinogen-induced tumor formation.

cancer biology↗

bioRxiv2023

Neuroinfectiology of an atypical anthrax-causing pathogen in wild chimpanzees

Bacillus cereus biovar anthracis (Bcbva) is an atypical anthrax-causing bacterium, inflicting wildlife fatalities across African rainforest ecosystems. The pathogens virulence in one of our closest living relatives, the chimpanzee, together with human serological evidence, suggests Bcbva is zoonotic. While classical B. anthracis-induced anthrax has been described to affect the central nervous system at a progressive disease-state, the neuroinfectiology of Bcbva is yet unknown. Here we characterised the pathogens neuro-invasiveness via gross pathological assessment, ultra-high resolution quantitative Magnetic Resonance Imaging and histological analysis on four brains, which were extracted from naturally deceased wild chimpanzees in Tai National Park, Cote dIvoire. Based on macroscopically evident pial vessel congestion and haemorrhages as well as cortical siderosis detected via MRI, we concluded that Bcbva induced meningitis analogous to B. anthracis. Further, histological visualisation of bacteria and leukocytes in the subarachnoid space evidenced the bacteriums capability to breach the arachnoid barrier. Bcbva was detected in the brain parenchyma of all four cases. This indicates a higher ability to transgress the glia limitans and therefore exhibits a higher neuroinvasiveness compared to B. anthracis that predominantly stays confined to the meninges. Heightened glial fibrillary acidic protein (GFAP) expression but little morphological gliosis suggest a rapid disease progression leading to host-death within hours to a few days after central nervous system invasion. Overall our results reveal Bcbvas ability to breach blood-brain barriers which results in a pronounced neuropathogenicity. Bcbva causes extensive damage to the meninges and the brain parenchyma, as well as rapid and massive digestion of brain extracellular matrix in chimpanzees and potentially so in humans in case of zoonotic spillover.

neuroscience↗

bioRxiv2023

Mechanistic basis of the dynamic response of TWIK1 ionic selectivity to pH

At neutral pH, the TWIK1 channel is highly selective for K+. When exposed to acidification, it becomes permeable to Na+. This change occurs within minutes and is reversible. By combining pKa calculations, molecular dynamics (MD) simulations, mutagenesis and electrophysiology, we identified a network of residues involved in this unique property. MD simulations captured crucial features associated with channel gating and previously observed by cryogenic electron microscopy (cryo-EM) at pH7.4 and pH5, such as the pH-dependent orientation of the lateral side chain of the proton sensor His122 and the elongation of the entire pore structure upon acidification. Between the closed and open states of TWIK1 observed by cryo-EM, MD simulations show that the channel undergoes additional conformational changes between pH 7.5 to 6 that involves the His122, Glu235, Lys246 and Phe109 residues. A complex network of interactions surrounding the selectivity filter at high pH transforms into a simple set of stronger interactions at low pH. In particular, His122 protonated by acidification moves away from Lys246 and engages in a salt bridge with Glu235. In addition, stacking interactions between Phe109 and His122, which stabilize the selectivity filter in its K+-selective state at high pH, disappear upon acidification. This causes dissociation of the Phe109 aromatic side chain from this network, ultimately leading to the Na+-permeable conformation of the channel.

biochemistry↗

bioRxiv2023

A signalling rheostat controls chromosome segregation fidelity during early lineage specification and neurogenesis by modulating DNA replication stress

The development and homeostasis of organisms rely on the correct replication, maintenance and segregation of their genetic blueprints. How these intracellular processes are monitored across generations of different human cellular lineages, and why the spatio-temporal distribution of mosaicism varies during development remain unknown. Here, we identify several lineage specification signals that regulate chromosome segregation fidelity in both human and mouse pluripotent stem cells. Through epistatic analyses, we find that that WNT, BMP and FGF form a signalling "rheostat" upstream of ATM that monitors replication fork velocity, origin firing and DNA damage during S-phase in pluripotency, which in turn controls spindle polymerisation dynamics and faithful chromosome segregation in the following mitosis. Cell signalling control of chromosome segregation fidelity declines together with ATM activity after pluripotency exit and specification into the three human germ layers, or further differentiation into meso- and endoderm lineages, but re-emerges during neuronal lineage specification. In particular, we reveal that a tug-of-war between FGF and WNT signalling in neural progenitor cells results in DNA damage and chromosome missegregation during cortical neurogenesis, which could provide a rationale for the high levels of mosaicism in the human brain. Our results highlight a moonlighting role of morphogens, patterning signals and growth factors in genome maintenance during pluripotency and lineage specification, which could have important implications for our understanding on how mutations and aneuploidy arise during human development and disease. One sentence summaryDevelopmental signals link genome maintenance to cell fate

cell biology↗

bioRxiv2022

Clonally resolved single-cell multi-omics identifies routes of cellular differentiation in acute myeloid leukemia

Inter-patient variability and the similarity of healthy and leukemic stem cells have impeded the characterization of leukemic stem cells (LSCs) in acute myeloid leukemia (AML), and their differentiation landscape. Here, we introduce CloneTracer, a novel method that adds clonal resolution to single-cell RNA-seq datasets. Applied to samples from 19 AML patients, CloneTracer revealed routes of leukemic differentiation. While residual healthy cells dominated the dormant stem cell compartment, active leukemic stem cells resembled their healthy counterpart and retained erythroid capacity. By contrast, downstream myeloid progenitors were highly aberrant and constituted the disease-defining compartment: Their gene expression and differentiation state determined both chemotherapy response and the leukemias ability to differentiate to transcriptomically normal monocytes. Finally, we demonstrated the potential of CloneTracer to identify surface markers mis-regulated specifically in leukemic cells by intra-patient comparisons. Taken together, CloneTracer revealed a differentiation landscape that mimics its healthy counterpart and determines biology and therapy response in AML.

cancer biology↗

bioRxiv2021

Single cell multi-omics analysis of chromothriptic medulloblastoma highlights genomic and transcriptomic consequences of genome instability

Chromothripsis is a form of genome instability, whereby a presumably single catastrophic event generates extensive genomic rearrangements of one or few chromosome(s). However, little is known about the heterogeneity of chromothripsis across different clones from the same tumor, as well as changes in response to treatment. We analyzed single-cell genomic and transcriptomic alterations linked with chromothripsis in human p53-deficient medulloblastoma (n=7). We reconstructed the order of somatic events, identified early alterations likely linked to chromothripsis and depicted the contribution of chromothripsis to malignancy. We characterized subclonal variation of chromothripsis and its effects on double-minute chromosomes, cancer drivers and putatively druggable targets. Furthermore, we highlighted the causative role and the fitness consequences of specific rearrangements in neural progenitors. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=85 SRC="FIGDIR/small/449944v1_ufig1.gif" ALT="Figure 1"> View larger version (27K): org.highwire.dtl.DTLVardef@9d30e4org.highwire.dtl.DTLVardef@1f4d34eorg.highwire.dtl.DTLVardef@5cd50corg.highwire.dtl.DTLVardef@a71a81_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2020

A versatile system to introduce clusters of genomic double-strand breaks in large cell populations

In vitro assays for clustered DNA lesions will facilitate the analysis of the mechanisms underlying complex genome rearrangements such as chromothripsis, including the recruitment of repair factors to sites of DNA double-strand breaks. We present a novel method generating localized DNA double-strand breaks using UV-irradiation with photomasks. The size of the damage foci and the spacing between lesions are fully adjustable, making the assay suitable for different cell types and targeted areas. We validated this set-up with genomically stable epithelial cells, normal fibroblasts, pluripotent stem cells and patient-derived primary cultures. Our method does not require a specialized device such as a laser, making it accessible to a broad range of users. Sensitization by BrdU incorporation is not required, which enables analyzing the DNA damage response in post-mitotic cells. Irradiated cells can be cultivated further, followed by time-lapse imaging or used for downstream biochemical analyses, thanks to the high-throughput of the system. Importantly, we showed genome rearrangements in the irradiated cells, providing a proof of principle for the induction of structural variants by localized DNA lesions.

genomics↗

bioRxiv2019

Induced aneuploidy disrupts MCF10A acini formation and CCND1 expression

Abnormal karyotypes, namely aneuploidy, can be detected in nearly all cancer entities at different grades. The impact of these altering mutations on epigenetic regulation, especially on promoter-enhancer interactions are not well understood. Here, we applied a 3D model of MCF10A cells in a high-content screen to measure induced aneuploidy by RNA interference of 82 mitotic genes associated with aneuploidy and breast cancer. Perturbation of ESPL1 and TOP2A expression led to increased mitotic instability and subsequent aneuploidy and polylobed nuclei. During acinus formation these polylobed cells disrupted proper acinus rotation inhibiting the development of a hollow lumen and a polarized outer cell layer. Further, gene expression profiling identified upregulated CCND1 among other breast cancer related genes. We show that acquisition of aneuploidy affects the morphogenesis of MCF10A acini and expression of cancer relevant genes. By conducting 4C chromosome capturing experiments we linked the alteration of interactions of the promoter region to CCND1 upregulation.

cancer biology↗

bioRxiv2018

Topokaryotyping demonstrates single cell variability and stress dependent variations in nuclear envelope associated domains

Analysis of large-scale interphase genome positioning with reference to a nuclear landmark has recently been studied using sequencing-based single cell approaches. However, these approaches are dependent upon technically challenging, time consuming and costly high throughput sequencing technologies, requiring specialized bioinformatics tools and expertise. Here, we propose a novel, affordable and robust microscopy-based single cell approach, termed Topokaryotyping, to analyze and reconstruct the interphase positioning of genomic loci relative to a given nuclear landmark, detectable as banding pattern on mitotic chromosomes. This is accomplished by proximity-dependent histone labeling, where biotin ligase BirA fused to nuclear envelope marker Emerin was coexpressed together with Biotin Acceptor Peptide (BAP)-histone fusion followed by (i) biotin labeling, (ii) generation of mitotic spreads, (iii) detection of the biotin label on mitotic chromosomes and (iv) their identification by karyotyping. Using Topokaryotyping, we identified both cooperativity and stochasticity in the positioning of emerin-associated chromatin domains in individual cells. Furthermore, the chromosome-banding pattern showed dynamic changes in emerin-associated domains upon physical and radiological stress. In summary, Topokaryotyping is a sensitive and reliable technique to quantitatively analyze spatial positioning of genomic regions interacting with a given nuclear landmark at the single cell level in various experimental conditions.

cell biology↗

bioRxiv2018

Defective DNA damage repair leads to frequent catastrophic genomic events in murine and human tumors

Chromothripsis and chromoanasynthesis are catastrophic events leading to clustered genomic rearrangements. Whole-genome sequencing revealed frequent chromothripsis or chromoanasynthesis (n= 16/26) in brain tumors developing in mice deficient for factors involved in homologous-recombination-repair or non-homologous-end-joining. Catastrophic events were tightly linked to Myc/Mycn amplification, with increased DNA damage and inefficient apoptotic response already observable at early postnatal stages. Inhibition of repair processes and comparison of the mouse tumors with human medulloblastomas (n=68) and glioblastomas (n=32) identified chromothripsis as associated with MYC/MYCN gains and with DNA repair deficiencies, pointing towards therapeutic opportunities to target DNA repair defects in tumors with complex genomic rearrangements.

cancer biology↗