Biology subjects

Kohler, H.

Publications and source records attributed to Kohler, H..

5 recordsLinked to original sources

bioRxiv2025

A scheduler for rhythmic gene expression

Genetic oscillators drive precisely timed gene expression, crucial for development and physiology. Using the C. elegans molting clock as a model, we investigate how oscillators can schedule the orderly expression of thousands of genes. Single cell RNA sequencing reveals a broad peak phase dispersion in individual issues, mirrored by rhythmic changes in chromatin accessibility at thousands of regulatory elements identified by time-resolved ATAC-seq. We develop a linear model to predict chromatin dynamics based on the binding of >200 transcription factors. This identifies nine key regulators acting additively to determine the peak phase and amplitude of each regulatory element. Strikingly, these factors can also generate constitutive, non-rhythmic activity through destructive interference. Validating its power, the model accurately predicts the impact of GRH-1/Grainyhead perturbation on both chromatin and transcript dynamics. This work provides a conceptual framework for understanding how combinatorial, non-cooperative transcription factor binding schedules complex gene expression patterns in development and other dynamic biological processes.

systems biology↗

bioRxiv2025

The eutherian-specific histone H3.4 promotes germ cell development and reproductive fitness

Many genes encoding chromatin proteins are subject to evolutionary selection driving reproductive fitness. In mice and men, the histone H3.4 variant is essential to spermatogenesis. Here we define the evolutionary origin and molecular-physiological roles of sequence variation in H3f4 for male germ cell development in mice. Our phylogenetic analyses indicate that eutherian H3f4 orthologs originate from an ancestral H3.2 gene existing prior to the divergence of eutherian and marsupial mammals over 100 million years ago. Positioned in truncated histone gene clusters, eutherian H3f4 orthologs show increased non-synonymous and synonymous substitution rates compared to orthologous marsupial H3.2 loci located in typically large histone clusters. To determine the impact of sequence divergence on reproductive fitness, we reverted non-synonymously substituted residues in H3f4 to those present in canonical H3.1 (H3f4V24A, H3f4H42R, H3f4S98A). Hemizygous expression of such triply reverted H3f4H3.1 allele on a H3f4-deficiency background caused an >40% reduction in testis weight associated with impaired meiotic DNA double strand break repair, death of pachytene spermatocytes, impaired differentiation of spermatids and aberrant expression of thousands of genes during spermatid elongation. Hemizygous expression of individual residue substitution alleles revealed residues V24 and H42 of H3.4 to promote spermatogenesis, while residue S98 is neutral. Together, our study shows that H3f4 has been subject to positive evolutionary selection, promoting male reproductive fitness.

genetics↗

bioRxiv2024

Ubiquitination mediates protein localization in RNA virus-infected cells

Viruses trigger monocytes proinflammatory and antiviral responses. Ubiquitination, a post-translational modification primarily marking proteins for degradation, regulates cellular responses to virus infection. However, a comprehensive analysis of virus-induced ubiquitination in monocytes is lacking. Here we identified a widespread increase of ubiquitination under viral RNA challenge or influenza infection in monocytes. Systematic proteome studies revealed that influenza infection elicits dynamic ubiquitinome alterations, with a notable transition from early to late stage. Most of this increased ubiquitination is not proteolytic and targets proteins involved in subcellular localization, such as the mitochondrial protein COA7 which, when ubiquitinated during infection, translocates to the nucleus and inhibits stress granules formation and TNF- expression. Blocking ubiquitination halts viral ribonucleoproteins nuclear export, highlighting ubiquitinations importance for protein localization during virus infection.

molecular biology↗

bioRxiv2022

Single-cell analysis reveals inter- and intratumour heterogeneity in metastatic breast cancer

Metastasis is the leading cause of cancer-related deaths of breast cancer patients. Some cancer cells in a tumour go through successive steps, referred to as the metastatic cascade, and give rise to metastases at a distant site. We know that the plasticity and heterogeneity of cancer cells play critical roles in metastasis but the precise underlying molecular mechanisms remain elusive. Here we aimed to identify molecular mechanisms of metastasis during colonization, one of the most important yet poorly understood steps of the cascade. We performed single-cell RNA-Seq (scRNA-Seq) on tumours and matched lung macrometastases of patient-derived xenografts of breast cancer. After correcting for confounding factors such as the cell cycle and the percentage of detected genes (PDG), we identified cells in three states in both tumours and metastases. Gene-set Enrichment Analysis revealed biological processes specific to proliferation and invasion in two states. Our findings suggest that these states are a balance between epithelial-to-mesenchymal (EMT) and mesenchymal-to-epithelial transitions (MET) traits that results in so-called partial EMT phenotypes. Analysis of the top Differentially Expressed Genes (DEGs) between these cell states revealed a common set of partial EMT Transcriptions Factors (TFs) controlling gene expression, including ZNF750, OVOL2, TP63, TFAP2C and HEY2. Our data suggest that the TFs related to EMT delineate different cell states in tumours and metastases. The results highlight the marked interpatient heterogeneity of breast cancer but identify common features of single cells from five models of metastatic breast cancer.

cancer biology↗

bioRxiv2021

Nonlinear control of transcription through enhancer-promoter interactions

Chromosome structure in mammals is thought to regulate transcription by modulating the three-dimensional interactions between enhancers and promoters, notably through CTCF-mediated interactions and topologically associating domains (TADs)1-4. However, how chromosome interactions are actually translated into transcriptional outputs remains unclear. To address this question we use a novel assay to position an enhancer at a large number of densely spaced chromosomal locations relative to a fixed promoter, and measure promoter output and interactions within a genomic region with minimal regulatory and structural complexity. Quantitative analysis of hundreds of cell lines reveal that the transcriptional effect of an enhancer depends on its contact probabilities with the promoter through a non-linear relationship. Mathematical modeling and validation against experimental data further provide evidence that nonlinearity arises from transient enhancer-promoter interactions being memorized into longer-lived promoter states in individual cells, thus uncoupling the temporal dynamics of interactions from those of transcription. This uncovers a potential mechanism for how enhancers control transcription across large genomic distances despite rarely meeting their target promoters, and for how TAD boundaries can block distal enhancers. We finally show that enhancer strength additionally determines not only absolute transcription levels, but also the sensitivity of a promoter to CTCF-mediated functional insulation. Our unbiased, systematic and quantitative measurements establish general principles for the context-dependent role of chromosome structure in long-range transcriptional regulation.

molecular biology↗