Biology subjects

Glaser, S.

Publications and source records attributed to Glaser, S..

5 recordsLinked to original sources

bioRxiv2024

Replisome passage through the cohesin ring

Following eukaryotic genome replication, the two newly synthesised sister chromatids remain paired by the ring-shaped cohesin complex, enabling their faithful segregation to daughter cells during cell divisions1. Cohesin topologically embraces DNA already before DNA replication2-5, and replisome passage through the cohesin ring is thought of as a fail-safe mechanism ensuring that cohesin entraps both replication products6,7. Whether replisomes indeed pass through cohesin rings remains unknown. Here, we use biochemical reconstitution4,8,9 and single molecule fluorescence microscopy to directly visualise replisome-cohesin encounters. We find that the translocating eukaryotic replicative Cdc45-Mcm2-7-GINS (CMG) helicase is frequently an obstacle to cohesin, but that the likelihood with which CMG passes cohesin increases in the presence of replisome components with known sister chromatid cohesion functions7,10-14, or by preventing cohesin from freely sliding along the template DNA. Cohesin retains topological DNA entrapment during CMG passage, suggesting that the helicase passes through the ring. The passage frequency increases further when fully reconstituted replisomes encounter cohesin rings, resulting in successful establishment of cohesion between the two replication products. Our findings demonstrate the existence of a simple mechanism that links genome replication with chromosome segregation, replisome passage through cohesin rings.

molecular biology↗

bioRxiv2022

Development of Scaffold-free 3D Cholangiocyte Organoids to Study the Progression of Primary Sclerosing Cholangitis

Organoids are novel in vitro models to study intercellular crosstalk between the different types of cells in the pathophysiology of disease. To better understand the underlying mechanisms driving the progression of primary sclerosing cholangitis (PSC), we developed scaffold-free multi-cellular 3D cholangiocyte organoids (3D-CHO) using primary liver cell lines derived from normal and PSC patients. Human liver samples from healthy donors and late-stage PSC patients were used to isolate primary cholangiocytes (EPCAM+/CK-19+), liver endothelial cells (LECs, CD31+), and hepatic stellate cells (HSCs, CD31-/CD68-/Desmin+/Vitamin A+). 3D-CHOs were formed using cholangiocytes:HSCs:LECs and kept viable for up to 1 month. Isolated primary cell lines and 3D-CHOs were further characterized by immunofluorescence (IF), qRT-PCR, and transmission electron microscopy. Gene expressions for cholangiocytes (SOX9, CFTR, EpCAM, AE, SCT, SCTR), fibrosis (ACTA2, COL1A1, DESMIN, TGF{beta}1), angiogenesis (PECAM, VEGF, CDH5, vWF), and inflammation (IL-6, TNF-) confirmed PSC phenotypes of 3D-CHOs. Since cholangiocytes develop a neuroendocrine phenotype and express neuromodulators, confocal-IF demonstrated that neurokinin-1 receptor (NK-1R, expressed by cholangiocytes and upregulated in PSC), was localized within CK-19+ cholangiocytes. Moreover, 3D-CHOs from PSC patients confirmed PSC phenotypes with upregulated NK-1R, tachykinin precursor 1, and downregulated membrane metalloendopeptidase. Our viable scaffold-free multiple-cell 3D-CHOs showed superiority as an in vitro model in mimicking PSC in vivo phenotypes compared to 2D cell culture, which can be used in PSC disease-related research.

bioengineering↗

bioRxiv2020

Use of waggle dance information in honey bees is linked to gene expression in the antennae, but not in the brain

Communication is essential for social animals, but deciding how to utilize information provided by conspecifics is a complex process that depends on environmental and intrinsic factors. Honey bees use a unique form of communication, the waggle dance, to inform nestmates about the location of food sources. However, as in many other animals, experienced individuals often ignore this social information and prefer to rely on prior experiences, i.e. private information. The neurosensory factors that drive the decision to use social information are not yet understood. Here we test whether the decision to use social dance information or private information is linked to gene expression differences in different parts of the nervous system. We trained bees to collect food from sugar water feeders and observed whether they utilize social or private information when exposed to dances for a new food source. We performed transcriptome analysis of four brain parts critical for cognition: the subesophageal ganglion, the central brain, the mushroom bodies, and the antennal lobes but, unexpectedly, detected no differences between social or private information users. In contrast, we found 413 differentially expressed genes in the antennae, suggesting that variation in sensory perception mediate the decision to use social information. Social information users were characterized by the upregulation of dopamine and serotonin genes while private information users upregualted several genes coding for odor perception. These results highlight that decision making in honey bees might also depend on peripheral processes of perception rather than higher-order brain centers of information integration.

animal behavior and cognition↗

bioRxiv2020

BCL-XL is essential for the protection from secondary anemia caused by radiation-induced fatal kidney damage

Studies of gene-targeted mice identified the roles of the different pro-survival BCL-2 proteins during embryogenesis, but less is known about the roles of these proteins in adults, including in the response to cytotoxic stresses, such as treatment with anti-cancer agents. We investigated the role of BCL-XL in adult mice using a strategy where prior bone marrow transplantation allowed for loss of BCL-XL exclusively in non-hematopoietic tissues to prevent anemia caused by BCL-XL-deficiency in erythroid cells. Unexpectedly, the combination of total-body {gamma}-irradiation (TBI) and genetic loss of Bcl-x caused secondary anemia resulting from chronic renal failure due to apoptosis of renal tubular epithelium with secondary obstructive nephropathy. These findings identify a critical protective role of BCL-XL in the adult kidney and inform on the use of BCL-XL inhibitors in combinations with DNA damage-inducing drugs for cancer therapy. SummaryThe inducible loss of BCL-XL in all cells of adult mice causes primary anemia due to apoptosis of erythroid and megakaryocytic cell populations. In contrast {gamma}-radiation plus loss of BCL-XL in all cells except hematopoietic cells causes secondary anemia resulting from kidney damage.

pharmacology and toxicology↗

bioRxiv2019

Large body size variation is linked to low communication success in tandem running ants

Diversity in animal groups is often assumed to increase group performance. In insect colonies, genetic, behavioral and morphological variation among workers can improve colony functioning and resilience. However, it has been hypothesized that during communication processes, differences between workers, e.g. in body size, could also have negative effects. Tandem running is a common recruitment strategy in ants and allows a leader to guide a nestmate follower to resources. A substantial proportion of tandem runs fail because leader and follower loose contact. Using the ant Temnothorax nylanderi as a model system, we tested the hypothesis that tandem running success is impaired if leader and follower differ in size. Indeed, we found that the success rate of tandem pairs drops considerably as size variation increases: only ~7% of tandem runs were successful when the leader-follower size difference exceeded 10%, whereas 80% of tandem runs were successful when ants differed less than 5% in body length. One possible explanation is that ant size is linked to the preferred walking speed. Ants did not choose partners of similar size, but extranidal workers were larger than intranidal workers, which could reduce recruitment mistakes because it reduced the chance that very large and very small ants perform tandem runs together. Our results suggest that phenotypic differences between interacting workers can have negative effects on the efficiency of communication processes. Whether phenotypic variation has positive or negative effects is likely to depend on the task and the phenotypic trait that shows variation.

animal behavior and cognition↗