Rapid proteolysis of RAD21 in primary cells defines the role of cohesin in cell type-specific gene expression

Cohesin contributes to the organisation of the mammalian genome in 3D space, but its role in gene regulation remains poorly understood. To address this role, I have implemented a system that enables temporal control over cohesin function in primary mammalian cells by the inducible cleavage of the essential cohesin subunit RAD21, using tobacco etch virus protease (RAD21-TEV). Building on previous work in the lab that had linked cohesin to the expression of inflammatory genes, I used RAD21-TEV to show that genes encoding key mediators of the macrophage inflammatory response are directly reliant on cohesin for their correct expression. The deregulation of these genes led to the collapse of the macrophage response to microbial signals. I next investigated the role of cohesin in neuronal gene expression, because patients with mutations in cohesin and cohesin regulators show intellectual disability as a feature of Cornelia de Lange Syndrome (CdLS). Using RAD21-TEV in mature mouse neurons, I was able to show that acute and chronic cohesin depletion resulted in similar deregulation of neuronal genes. This indicated that cohesin was continuously required for neuronal gene expression. Interestingly, cohesin-dependent neuronal gene expression could be rescued by restoring cohesin after a period of cohesin depletion. To test the relevance of these findings to human disease, I isolated neuronal nuclei from postmortem CdLS and control brains. RNA-sequencing showed similar gene expression changes in human as in mouse cohesin-deficient neurons. These studies advance our understanding of cohesin's role in gene regulation, and suggest that the impact of cohesin deficiency on neuronal gene expression may in principle be reversible.Open Acces