Biology subjects

Bageritz, J.

Publications and source records attributed to Bageritz, J..

6 recordsLinked to original sources

bioRxiv2025

Gradient of Wnt signaling facilitates Mef2 heterogeneity and limits commitment of the developmental muscle progenitor pool

During skeletal muscle development, the timing and extent of lineage commitment towards differentiation must be coordinated to ensure proper tissue formation while preserving undifferentiated progenitors for adult stem cell function. This balance requires spatial and temporal regulation of cell fate and transcriptional regulators to act as key mediators of lineage progression. The transcription factor Mef2 is a key activator of myogenic differentiation across vertebrates and invertebrates. However, the mechanisms that spatially restrict Mef2 expression within the developing niche to limit muscle progenitor (MP) commitment towards differentiation remains less well characterized. Using the developmental flight muscle progenitor niche in Drosophila, a system that parallels vertebrate myogenesis, we investigated the transcriptional and spatial regulation of MP fate at a developmental timepoint when Mef2 expression begins to rise but precedes overt differentiation. We identified a spatially distinct subpopulation of MPs with low Mef2 expression and elevated Wnt/{beta}-catenin signaling. Within the broader MP pool, graded Wnt activity emerged as a key source of Mef2 heterogeneity: high Wnt activity led to strong repression of Mef2 via Armadillo/{beta}-catenin and TCF-dependent regulation. Moderate Wnt activity, meanwhile, not only repressed Mef2 expression but also sustained expression of zfh1, a conserved transcription factor linked to MP maintenance and adult muscle stem cell identity. Contrary to its well-established role in promoting myogenesis, Wnt/{beta}-catenin signaling in this early spatial context instead promotes a less committed state, leading to a subset of MPs with particular low Mef2 level. These findings highlight greater spatial complexity within the developing muscle progenitor niche than previously recognized, with potential implications for conserved strategies of muscle stem cell regulation across species.

developmental biology↗

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↗

bioRxiv2023

An ancient split of germline and somatic stem cell lineages in Hydra

In many animals, germ cell segregation occurs during early embryogenesis to protect the genome, but its origin in basal metazoans is controversial. Here, we show in the freshwater polyp Hydra by clonal analysis and transgenic animals that interstitial stem cells comprise two separate stem cell populations, i.e., germline and multipotent somatic stem cells. We isolated genetically labelled stem cells for a global transcriptome study and discovered a broad set of germline-specific/enriched genes including Prdm9, Pax5, Dmrt1. In an alternative splicing analysis, we identified many genes with germline-specific isoforms; among them, male-specific isoforms of Dmrt1 and Snf5. The somatic interstitial stem cell lineage was characterized by numerous neuronal control genes like Neurog. But all stem cells in Hydra also share a core of stemness genes that has its roots in unicellular eukaryotes. This suggests an evolutionary scenario in which, at the emergence of animal multicellularity, there was an early split into a stable germline and different somatic stem cell lineages.

developmental biology↗

bioRxiv2021

Glyoxal as alternative fixative for single cell RNA sequencing

Single cell RNA sequencing (scRNA-seq) has become an important method to identify cell types, delineate the trajectories of cell differentiation in whole organisms and understand the heterogeneity in cellular responses. Nevertheless, sample collection and processing remain a severe bottleneck for scRNA-seq experiments. Cell isolation protocols often lead to significant changes in the transcriptomes of cells, requiring novel methods to preserve cell states. Here, we developed and benchmarked protocols using glyoxal as a fixative for scRNA-seq application. Using Drop-seq methodology, we detected high numbers of transcripts and genes from glyoxal-fixed Drosophila cells after scRNA-seq. The effective glyoxal fixation of transcriptomes in Drosophila and human cells was further supported by a high correlation of gene expression data between glyoxal-fixed and unfixed samples. Accordingly, we also found highly expressed genes overlapping to a large extent between experimental conditions. These results indicated that our fixation protocol did not induce considerable changes in gene expression and conserved the transcriptome for subsequent single cell isolation procedures. In conclusion, we present glyoxal as a suitable fixative for Drosophila cells and potentially cells of other species that allows high-quality scRNA-seq applications.

genomics↗

bioRxiv2020

Establishment of a simplified preparation method for single-nucleus RNA-sequencing and its application to long-term frozen tumor tissues

Recent advances allowing the genomic analysis of individual cells from a bulk population have provided intriguing new insights into areas such as developmental processes and tumor heterogeneity. Most approaches to date, however, rely on the availability of fresh surgical specimens, thereby dramatically reducing the ability to profile particularly rare tissue types. Pediatric central nervous system tumors - the leading cause of childhood cancer deaths - represent one such example, where often only frozen rather than native material is available. Due to an increasing need for advanced techniques to understand the heterogeneity of these tumors, we optimized a method to isolate intact nuclei from long-term frozen pediatric glioma tissues. We performed a technical comparison between different single nucleus RNA-sequencing (snRNA-seq) systems using a patient-derived xenograft model as a test sample. Further, we applied the established nucleus isolation method to analyze frozen primary tissue from two pediatric central nervous system tumors - one pilocytic astrocytoma and one glioblastoma - allowing the identification of distinct tumor cell populations and infiltrating microglia. The results show that our fast, simple and low-cost nuclear isolation protocol provides intact nuclei, which can be used in both droplet-based 3 transcriptome amplification (10X Genomics) and plate-based whole transcriptome amplification (Fluidigm C1) single-cell sequencing platforms, thereby dramatically increasing the potential for application of such methods to rare entities.

cancer biology↗

bioRxiv2018

Gene expression atlas of a developing tissue by single cell expression correlation analysis

The Drosophila wing disc has been a fundamental model system for the discovery of key signaling pathways and for our understanding of developmental processes. However, a complete map of gene expression in this tissue is lacking. To obtain a complete gene expression atlas in the wing disc, we employed single-cell sequencing (scRNA-seq) and developed a new method for analyzing scRNA-seq data based on gene expression correlations rather than cell mappings. This enables us to discover 824 genes with spatially restricted expression patterns, and to compute expression maps for all genes in the wing disc. This approach identifies both known and new clusters of genes with similar expression patterns and functional relevance. As proof of concept, we characterize the previously unstudied gene CG5151 and show it regulates Wnt signaling. This novel method will enable the leveraging of scRNA-seq data for generating expression atlases of undifferentiated tissues during development.

developmental biology↗