Epigenetic effects of folate and related B vitamins on brain health throughout life: Scientific substantiation and translation of the evidence for health improvement strategies

Suboptimal status of folate and/or interrelated B vitamins (B12 , B6 and riboflavin) can perturb one-carbon metabolism and adversely affect brain development in early life and brain function in later life. Human studies show that maternal folate status during pregnancy is associated with cognitive development in the child, whilst optimal B vitamin status may help to prevent cognitive dysfunction in later life. The biological mechanisms explaining these relationships are not clear but may involve folate-related DNA methylation of epigenetically controlled genes related to brain development and function. A better understanding of the mechanisms linking these B vitamins and the epigenome with brain health at critical stages of the lifecycle is necessary to support evidence-based health improvement strategies. The EpiBrain project, a transnational collaboration involving partners in the United Kingdom, Canada and Spain, is investigating the nutrition-epigenome-brain relationship, particularly focussing on folate-related epigenetic effects in relation to brain health outcomes. We are conducting new epigenetics analysis on bio-banked samples from existing well-characterised cohorts and randomised trials conducted in pregnancy and later life. Dietary, nutrient biomarker and epigenetic data will be linked with brain outcomes in children and older adults. In addition, we will investigate the nutrition-epigenome-brain relationship in B vitamin intervention trial participants using magnetoencephalography, a state-of-the-art neuroimaging modality to assess neuronal functioning. The project outcomes will provide an improved understanding of the role of folate and related B vitamins in brain health, and the epigenetic mechanisms involved. The results are expected to provide scientific substantiation to support nutritional strategies for better brain health across the lifecycle.

A8 REPEATED SUBMERGENCE OF AIR-LIQUID INTERFACE COLONOID CULTURES IMPAIRS INFLAMMATORY AND REGENERATIVE RESPONSES

Background

Damage in the intestinal epithelium is repaired via de-differentiation of mature intestinal epithelial cells to a stem-like state. Indeed, literature has primarily focused on acute forms of intestinal damage, but there is a lack of models to study how intestinal stem cells function after chronic injury, such as in inflammatory bowel disease (IBD). A previous report found that growth of mouse intestinal organoids in air-liquid interface (ALI) follows by submergence caused differentiation and reversible injury, but this has not been demonstrated in human cells or with repeated cycles of injury. Understanding how chronic damage alters human intestinal stem cell fate and function is imperative to developing novel therapies that repair the epithelium in people with IBD

Aims

To develop a robust in vitro model to differentiate and damage human intestinal epithelial cells, with or without the addition of bacterial flagellin to mimic pathogen exposure.

Methods

Human colonoid monolayers were seeded on Transwell inserts for 10 days until fully confluent and then differentiated by removing the apical media to create ALI growth conditions for 7 days. To induce damage, media was added to the apical side of the Transwell, with or without the addition of flagellin in the basolateral compartment. Following submergence induced damage, the apical media was removed and collected for chemokine analysis, and the cells were grown back in ALI for 3 days to recover them from injury. This cycle was repeated 5 times to induce chronic damage. Cells were collected for qPCR analysis, immunofluorescence imaging, RNA sequencing and DNA methylation analysis

Results

Repeated rounds of damage impaired the ability of intestinal epithelial cells (IECs) to respond to TLR stimulation (a decrease in basolateral IL-8 with each round), likely due to a decrease in TLR signaling pathways, as demonstrated by GSEA and qPCR. Chronic submergence damage led to an increase in differentiation of cells expressing MUC2, SLC26a3 and CHGA, and a decrease in stemness as shown by qPCR for BMI1, HOPX, and LGR5. After several rounds of damage, colonoid monolayers were unable to regrow as monolayers after passaging, likely due to a decrease in YAP signaling. We also identified mRNA expression and DNA methylation changes in genes associated with IBD and colon cancer.

Conclusions

We have developed a novel chronic damage model of recurrent IEC injury, which possibly mimics pathologies seen in people with inflammatory bowel disease. This model can be used to understand how chronic damage alters the ability of IECs to respond to pathogens and regenerate to repair and protect the epithelium from further damage.

Funding Agencies

CCC

Identification of a nucleic acid-binding region within the largest subunit of Drosophila melanogaster RNA polymerase II

The largest and the second-largest subunit of the multisubunit eukaryotic RNA polymerases are involved in interaction with the DNA template and the nascent RNA chain. Using Southwestern DNA-binding techniques and nitrocellulose filter binding assays of bacterially expressed fusion proteins, we have identified a region of the largest, 215-kDa, subunit of Drosophila RNA polymerase II that has the potential to bind nucleic acids nonspecifically. This nucleic acid-binding region is located between amino acid residues 309-384 and is highly conserved within the largest subunits of eukaryotic and bacterial RNA polymerases. A homology to a region of the DNA-binding cleft of Escherichia coli DNA polymerase I involved in binding of the newly synthesized DNA duplex provides indirect evidence that the nucleic acid-binding region of the largest subunit participates in interaction with double-stranded nucleic acids during transcription. The nonspecific DNA-binding behavior of the region is similar to that observed for the native enzyme in nitrocellulose filter binding assays and that of the separated largest subunit in Southwestern assays. A high content of basic amino acid residues is consistent with the electrostatic nature of nonspecific DNA binding by RNA polymerases.