Parkinson’s disease (PD) is a complex neurodegenerative condition that affects more than 7 million people worldwide and often occurs after the age of 65. The main hallmark of PD is the selective loss of dopaminergic neurons from substantia nigra, which control voluntary movement. Despite recent advances, current PD treatments only ameliorate symptoms but do not prevent neuronal loss and cannot cure the disease. PD aetiology is multifactorial, with genetic and environmental factors interacting via as yet unclear mechanisms to induce PD pathology. Recent studies have proposed that environmental and genetic factors may trigger hyperactivation of DNA mobile elements. These elements can alter the genome by insertional mutagenesis, recombination and deletion, potentially contributing to the susceptibility and pathophysiology of neurological disorders. Long interspersed element-1 (L1) is the only active and autonomous mobile element in the human genome, and accounts for about 17% of human DNA. L1 is active in somatic cells and can ‘jump‘ from one place in the genome to another by first copying itself into RNA and then reversing the process, thus potentially altering the activity of genes were they relocate. We aim to investigate the role of L1 activity at the intersection of environmental and genetic factors known to contribute to PD aetiology and deepen our understanding of how PD develops. Currently, we are establishing the core parameters of L1 mobilisation in PD and also test whether these somatic variants are likely to alter dopaminergic neuron phenotype. To achieve these aims, the project is using imaging techniques in a mouse model combined with genomics in mouse and human samples.