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.