CEBS update: curated toxicology database with enhanced tools for data integration.

The Chemical Effects in Biological Systems database (CEBS) contains extensive toxicology study results and metadata from the Division of the National Toxicology Program (NTP) and other studies of environmental health interest. This resource grants public access to search and collate data from over 10 250 studies for 12 750 test articles (chemicals, environmental agents). CEBS has made considerable strides over the last 5 years to integrate growing internal data repositories into data warehouses and data marts to better serve the public with high quality curated datasets. This effort includes harmonizing legacy terms and metadata to current standards, mapping test articles to external identifiers, and aligning terms to OBO (Open Biological and Biomedical Ontology) Foundry ontologies. The data are made available through the CEBS Homepage (https://cebs.niehs.nih.gov/cebs/), guided search applications, flat files on FTP (file transfer protocol), and APIs (application programming interface) for user access and to provide a bridge for computational tools. The user interface is intuitive with a single search bar to query keywords related to study metadata, publications, and data availability. Results are consolidated to single pages for each test article with NTP conclusions, publications, individual studies, data collections, and links to related test articles and projects available together.

Functional impact of cancer-associated cohesin variants on gene expression and cellular identity.

Cohesin is a ring-shaped protein complex that controls dynamic chromosome structure. Cohesin activity is important for a variety of biological processes, including formation of DNA loops that regulate gene expression. The precise mechanisms by which cohesin shapes local chromosome structure and gene expression are not fully understood. Recurrent mutations in cohesin complex members have been reported in various cancers, though it is not clear whether many cohesin sequence variants have phenotypes and contribute to disease. Here, we utilized CRISPR/Cas9 genome editing to introduce a variety of cohesin sequence variants into murine embryonic stem cells and investigate their molecular and cellular consequences. Some of the cohesin variants tested caused changes to transcription, including altered expression of gene encoding lineage-specifying developmental regulators. Altered gene expression was also observed at insulated neighborhoods, where cohesin-mediated DNA loops constrain potential interactions between genes and enhancers. Furthermore, some cohesin variants altered the proliferation rate and differentiation potential of murine embryonic stem cells. This study provides a functional comparison of cohesin variants found in cancer within an isogenic system, revealing the relative roles of various cohesin perturbations on gene expression and maintenance of cellular identity.

Distinct and overlapping roles of STAG1 and STAG2 in cohesin localization and gene expression in embryonic stem cells.

BACKGROUND: The three-dimensional organization of the genome in the nucleus plays an integral role in many biological processes, including gene expression. The genome is folded into DNA loops that bring together distal regulatory elements and genes. Cohesin, a ring-shaped protein complex, is a major player in the formation of DNA loops. Cohesin is composed of a core trimer and one of two variant STAG subunits, STAG1 or STAG2. It is not understood whether variant STAG proteins give rise to cohesin complexes with distinct functions. Recent studies have begun to characterize the roles of STAG1 and STAG2, with partially contradictory results. RESULTS: Here, we generate stable single-knockout embryonic stem cell lines to investigate the individual contributions of STAG1 and STAG2 in regulating cohesin chromosomal localization and function. We report both overlapping roles for STAG1 and STAG2 in cohesin localization and somewhat distinct roles in gene expression. STAG1 and STAG2 occupy the same sites across the genome, yet do not exist together in a higher order complex. Despite their shared localization, STAG1 and STAG2 have both distinct and redundant effects on gene expression. Loss of both STAG1 and STAG2 causes widespread transcriptome dysregulation, altered cohesin DNA occupancy, and reduced cell proliferation. CONCLUSIONS: Together, this work reveals the requirement of at least one STAG protein for proper cohesin function. STAG1 and STAG2 have independent roles in cohesin localization and both overlapping and distinct roles in gene expression. The roles of STAG1 and STAG2 in mouse embryonic stem cells may be somewhat different than in other cell types, due to their relative expression levels. These results advance our understanding of the link between mammalian genome organization and gene expression during development and disease contexts.