Biology subjects

Erb, C.

Publications and source records attributed to Erb, C..

4 recordsLinked to original sources

bioRxiv2022

Context-dependent transcriptional remodeling of TADs during differentiation

Metazoan chromosomes are organized into discrete domains (TADs), believed to contribute to the regulation of transcriptional programs. Despite extensive correlation between TAD organization and gene activity, a direct mechanistic link is unclear, with perturbation studies often showing little effect. To follow TAD dynamics during development, we used Capture Hi-C to interrogate the TADs around key differentially expressed genes during mouse thymocyte maturation, uncovering specific remodeling events. Notably, one TAD boundary was broadened to accommodate RNA polymerase elongation past the border, and sub-domains were formed around some activated genes without changes in CTCF binding. The ectopic induction of one gene was sufficient to recapitulate microdomain formation in embryonic stem cells, providing strong evidence that transcription can directly remodel chromatin structure. These results suggest that transcriptional processes drive complex, but non-universal, chromosome folding patterns that can be important in certain genomic contexts.

genomics↗

bioRxiv2021

Spermidine dampens inflammation by directly inhibiting Th17 cytokine production through a PRDX1 associated antioxidant pathway

The activation of IL-17 signaling has been linked to the pathogenesis of many chronic, inflammatory lung diseases including Cystic Fibrosis (CF). Through unbiased single-cell RNAseq screening, we found that IL-17+ T cells highly express Srm and Smox, which encode two key enzymes for spermidine synthesis. Spermidine has been shown to reduce inflammation by regulating macrophage activation and balancing Th17/Treg differentiation, but its direct effects on Th17 cytokine production has not been carefully investigated. Here, using already differentiated Th17 cells from cultured mouse splenocytes, we found that exogenous spermidine directly inhibits IL-1{beta}/IL-23 induced IL-17 production. Blockade of endogenous spermidine synthesis enhanced IL-17 production above native levels, further supporting that spermidine is a direct regulator of cytokine secretion independent of differentiation. In vivo, spermidine alleviates lung inflammation in both PA infection and LPS induced acute lung injury models. Further RNA-seq analysis suggests spermidine suppression of Th17 cytokine production is mediated through its PRDX1 dependent antioxidant activity. Our data establishes that spermidine is a direct regulator of Type-17 T cell cytokine production and has potent anti-inflammatory effects against lung inflammation.

immunology↗

bioRxiv2020

Archaeal SepF is essential for cell division in Haloferax volcanii

Bacterial cell division has been studied for decades but reports on the different archaeal cell division systems are rare. In many archaea, cell division depends on the tubulin homolog FtsZ, but further components of the divisome in these archaea are unknown. The halophilic archaeon Haloferax volcanii encodes two FtsZ homologs with different functions in cell division and a putative SepF homolog. In bacteria, SepF is part of the divisome and is recruited early to the FtsZ ring, where it most likely stimulates FtsZ ring formation. H. volcanii SepF co-localized with FtsZ1 and FtsZ2 at midcell. Overexpression of SepF had no effect on cell morphology, but no sepF deletion mutants could be generated. SepF depletion led to a severe cell division defect, resulting in cells with a strongly increased size. Overexpression of FtsZ1- and FtsZ2-GFP in SepF-depleted cells resulted in filamentous cells with an increasing number of FtsZ1 rings depending on the cell length, whereas FtsZ2 rings were not increased. Pull-down assays with HA-tagged SepF identified an interaction with FtsZ2 but not with FtsZ1. Archaeal SepF homologs lack the conserved glycine residue important for polymerization in bacteria and the H. volcanii SepF was purified as a dimer, suggesting that in contrast to the bacterial SepF homologs, polymerization does not seem to be important for its function. A model is proposed where first the FtsZ1 ring is formed and where SepF recruits FtsZ2 to the FtsZ1 ring, resulting in the formation of the FtsZ2 ring. This study provides important novel insights into cell division in archaea and shows that SepF is an important part of the divisome in FtsZ containing archaea.

microbiology↗

bioRxiv2019

Sample demultiplexing, multiplet detection, experiment planning and novel cell type verification in single cell sequencing

Identifying and removing multiplets from downstream analysis is essential to improve the scalability and reliability of single cell RNA sequencing (scRNA-seq). High multiplet rates create artificial cell types in the dataset. Sample barcoding, including the cell hashing technology and the MULTI-seq technology, enables analytical identification of a fraction of multiplets in a scRNA-seq dataset.\n\nWe propose a Gaussian-mixture-model-based multiplet identification method, GMM-Demux. GMM-Demux accurately identifies and removes the sample-barcoding-detectable multiplets and estimates the percentage of sample-barcoding-undetectable multiplets in the remaining dataset. GMM-Demux describes the droplet formation process with an augmented binomial probabilistic model, and uses the model to authenticate cell types discovered from a scRNA-seq dataset.\n\nWe conducted two cell-hashing experiments, collected a public cell-hashing dataset, and generated a simulated cellhashing dataset. We compared the classification result of GMM-Demux against a state-of-the-art heuristic-based classifier. We show that GMM-Demux is more accurate, more stable, reduces the error rate by up to 69x, and is capable of reliably recognizing 9 multiplet-induced fake cell types and 8 real cell types in a PBMC scRNA-seq dataset.

bioinformatics↗