ECCO Grant Serotonin gets into your genes: the role of histone serotonylation in inflammatory response and visceral hypersensitivity in Crohn’s Disease

More than 70% of CD patients experience visceral hypersensitivity (VH) despite reaching remission. VH treatment is difficult because the mechanism of its complication is unknown. Serotonin is mainly produced in the gut and regulates several physiological processes, such as intestinal immunity and pain. Disturbances in serotonin levels are associated with CD severity and VH. Intriguingly, we have recently observed that serotonin can covalently bind to glutamine at position 5 on histone H3 tail, leading to histone serotonylation (H3Q5ser) in peripheral blood mononuclear cells (PBMCs). Another study has demonstrated that H3Q5ser can also occur in cultured neuronal cells. Our objective is to investigate the role of this newly discovered epigenetic signature (H3Q5ser) in immune cells and enteric neurons in CD and its potential impact on the transcriptional programs of the inflammatory response and VH. To accomplish this goal, we will first determine the concentrations of serotonin in the mucosa and serum of active CD patients compared to healthy controls and establish how these levels relate to the enhancement of H3Q5ser in immune cells and enteric neurons. To study the functional role of H3Q5ser in cell activation, we will use site-directed or oligonucleotide- mediated mutagenesis to induce a point mutation in cultured enteric neuron cell lines and PBMCs to remove the binding site for serotonin on histone. Both wild-type and mutant cells will be incubated with or without serotonin and subjected to chromatin immunoprecipitation sequencing and RNA sequencing profiling to investigate the effect of H3Q5ser on the transcriptional programs associated with inflammation and VH. This project will provide a comprehensive understanding of the impact of the changes in serotonin concentrations on H3Q5ser-related gene expression in CD- associated VH and the inflammatory response. Our anticipated impact is subsequent studies that monitor H3Q5ser in VH in CD patients during treatment.