A study of DNA methylation in the prefrontal cortex of heterozygous GBA1 mutant mice
Luke Stephen Weymouth, Jennifer L Imm, Millie Sander, Jonathan T Brown, Katie Lunnon, Adam R. Smith- Psychiatry and Mental health
- Cellular and Molecular Neuroscience
- Geriatrics and Gerontology
- Neurology (clinical)
- Developmental Neuroscience
- Health Policy
- Epidemiology
Abstract
Background
Epigenome‐wide association studies (EWAS) of DNA methylation are being undertaken in Parkinson’s disease (PD) and Dementia with Lewy bodies (DLB) post‐mortem brain to identify novel disease mechanisms. However, there is considerable heterogeneity in clinical and neuropathological manifestation, as well as the contribution of post‐mortem factors, which can confound smaller studies. The heterozygous GBA1 (D409V/WT) mouse model of DLB presents α‐synuclein deposition, cognitive decline and cholinergic dysfunction. We have undertaken the first systematic investigation of DNA methylation in these mice to identify changes related to α‐synuclein deposition. We have also explored the effect of varying post‐mortem interval (PMI) on DNA methylation patterns, to allow us to better interpret human studies.
Method
In total we profiled DNA methylation using the Illumina Infinium Mouse Methylation BeadChip array in 58 mice, corresponding to 28 GBA1 D409V/WT and 30 WT mice aged 8‐23 months. Within each age group we divided mice into 5 further groups to also explore the effect of PMI: +0hrs, +24hrs, +48hrs, +72hrs & +96 hrs respectively. The mice were culled and those in the +0hrs group were immediately dissected with the prefrontal cortex being flash frozen and stored in the freezer. Mice assigned to other PMI groups were culled and stored at 4 degrees for the relevant PMI before dissection and flash freezing. DNA was extracted, bisulfite treated and then profiled for DNA methylation.
Result
Of the 58 mice that were sourced it was ensured that D409V/WT mice and WT mice were balanced between the 5 PMI groups. We have investigated the effect of phenotype, neuropathology and PMI on DNA methylation levels using linear regression models.
Conclusion
Teasing apart the effect varying PMI has on DNA methylation in post mortem brain samples will be a great aid when analysing such data going forward in large human EWASs. We have collated an in vivo study cohort to investigate DNA methylation patterns in the heterozygous D409V/WT mouse compared to WT, and interrogated the effect PMI has on the quality of methylation data. More broadly our study of PMI will have relevance to interpreting the results of human EWAS of DLB and other dementias.