Biology subjects

Zahnow, F.

Publications and source records attributed to Zahnow, F..

3 recordsLinked to original sources

bioRxiv2024

The evolutionary path of the epithelial sodium channel delta-subunit in Cetartiodactyla points to a role in sodium sensing

The epithelial sodium channel (ENaC) plays a key role in osmoregulation in tetrapod vertebrates and is a candidate receptor for salt taste sensation. There are four ENaC subunits (, {beta}, {gamma}, {delta}) which form {beta}{gamma}- or {delta}{beta}{gamma} ENaCs. While {beta}{gamma}-ENaC is a maintenance protein controlling sodium and potassium homeostasis, {delta}{beta}{gamma}-ENaC might represent a stress protein monitoring high sodium concentrations. The {delta}-subunit emerged with water-to-land transition of tetrapod vertebrate ancestors. We investigated the evolutionary path of ENaC-coding genes in Cetartiodactyla, a group comprising even-toed ungulates and the cetaceans (whales/dolphins) which transitioned from terrestrial to marine environments in the Eocene. The genes SCNN1A (-ENaC), SCNN1B ({beta}-ENaC) and SCNN1G ({gamma}-ENaC) are intact in all 22 investigated cetartiodactylan families. While SCNN1D ({delta}-ENaC) is intact in terrestrial Artiodactyla, it is a pseudogene in 12 cetacean families. A fusion of SCNN1D exons 11 and 12 under preservation of the open reading frame was observed in the Antilopinae, representing a new feature of this clade. Transcripts of SCNN1A, SCNN1B and SCNN1G were present in kidney and lung tissues of Bottlenose dolphins, highlighting {beta}{gamma}-ENaCs role as a maintenance protein. Consistent with SCNN1D loss, Bottlenose dolphins and Beluga whales did not show behavioural differences to stimuli with or without sodium in seawater-equivalent concentrations. These data suggest a function of {delta}-ENaC as a sodium sensing protein which might have become obsolete in cetaceans after the migration to high-salinity marine environments. Consistently, there is reduced selection pressure or pseudogenisation of SCNN1D in other marine mammals, including sirenians, pinnipeds and sea otter.

evolutionary biology↗

bioRxiv2024

Loss of SMARCB1 evokes targetable epigenetic vulnerabilities in Epithelioid Sarcoma

Dysfunction of epigenetic modulators, such as the SWI/SNF complex, is a wide-spread but relatively ill-defined feature of a broad spectrum of cancer entities. Among SWI/SNF-mutant entities, SMARCB1-deficient cancers, such as the highly aggressive Epithelioid Sarcoma (EpS), are characterized by this genetic event in an otherwise rather silent mutational landscape. This renders EpS an ideal model to study how epigenetic reprogramming by a single mutation can contribute to tumorigenesis. Hence, to characterize and compare the function of the SMARCB1-deficient, residual and the physiological SWI/SNF complex in cancer, we generated a panel of SMARCB1 re-expressing EpS cell lines and employed a functional multi-omics approach. Here, we show that SWI/SNF holds canonical characteristics of both tumor-suppressors and proto-oncogenes due to its multi-faceted role in the regulation of the epigenome. Our data indicates that the loss of SMARCB1 causes an overall loss of SWI/SNF chromatin affinity at cis-regulatory enhancer elements, inducing a preference for uncontrolled proliferation and cell cycle progression as opposed to development and differentiation. We further demonstrate that EpS cell lines depend on residual SWI/SNF action to maintain clonogenicity and proliferation. Consequently, EpS cell lines exhibit markedly increased sensitivity to pharmacological inhibition of the residual SWI/SNF when compared with SWI/SNF-proficient cancer entities. Collectively, our results from the EpS model shed new light on how a single mutation can rewire the pleiotropic effects of an epigenetic master regulator and provide inroads for therapeutic intervention.

cancer biology↗

bioRxiv2022

Chromosome 8 gain drives poor patient outcome via expression of 4E-BP1 in Ewing sarcoma

Chromosome 8 (chr8) gains are common in cancer. However, their potential contribution to tumor heterogeneity is largely unexplored. Ewing sarcoma (EwS) is characterized by pathognomonic FET::ETS fusions but a general paucity of other recurrent somatic mutations that could explain the observed clinical diversity. In EwS, chr8 gains are the second most common genetic alteration rendering EwS an ideal model to investigate the relevance of chr8 gains in an otherwise silent genomic context. Here, we report that chr8 gain-driven gene expression patterns correlate with poor overall survival of EwS patients. This effect is predominantly mediated by increased expression of the translation initiation factor binding protein 4E-BP1 encoded by EIF4EBP1 on chr8. High EIF4EBP1 expression showed the strongest association with poor patient survival among all chr8-encoded genes and correlated with chr8 gains in EwS tumors. Similar findings were made in numerous entities of The Cancer Genome Atlas (TCGA). Integrated multi-omics profiling uncovered that 4E-BP1 orchestrates a pro-proliferative proteomic network. Consistently, silencing of 4E-BP1 in the EwS model reduced cell proliferation, clonogenicity, spheroidal growth in vitro, and tumorigenesis in vivo. Drug screens and functional assays revealed that high 4E-BP1 expression sensitizes for pharmacological CDK4/6 inhibition in preclinical models. Collectively, we establish chr8 gains and high 4E-BP1 expression as prognostic biomarkers in EwS and demonstrate that their association with patient outcome is primarily mediated by 4E-BP1 orchestrating a pro-proliferative proteomic network sensitizing EwS for CDK4/6 inhibitors. Our data suggest that testing for chr8 gains may improve risk-stratification and therapeutic management in EwS and other cancers.

cancer biology↗