Microglia programs under PARK7/DJ-1 deficiency, a genetic cause of Parkinson's disease

Microglia, the resident immune cells of the central nervous system, play a critical role in neuroinflammatory responses associated with Parkinson’s disease (PD). Their activation and the resulting inflammatory cascades are significant contributors to PD pathology, especially in the pres-ence of oxidative stress. Approximately 10% of PD cases are linked to genetic factors, including mu-tations in the PARK7 gene that lead to a deficiency in DJ-1, a protein with vital antioxidant functions. DJ-1 is known to protect cells against reactive oxygen species, but the specific mechanisms by which DJ-1 deficiency contributes to the development of early-onset PD remain unclear. We sum-marize and discuss the functions of DJ-1 in microglia and find a significant effect on its immune and neuroinflammatory responses. This PhD project explores microglial transcriptional, functional and morphological changes during DJ-1 deficiency between PARK7/DJ-1 knockout (KO) mice and wildtype (WT) controls. Both groups were evaluated under baseline conditions and after adminis-tering lipopolysaccharide (LPS) to induce an immune response for 6 and 24 hours. Through single-cell and bulk RNA sequencing, along with multicolor flow cytometry and immunofluores-cence analyses, we identified unique activation profiles in DJ-1-deficient microglia. We describe in detail an optimized protocol for extracting up to sixteen morphological features of microglia from mouse brain tissue. Our findings indicate that microglia isolated from PARK7/DJ-1 KO mice exhibit a unique transcrip-tional profile, particularly evident in type II interferon and DNA damage re-sponse signaling, following LPS stimulation compared to wildtype mice. Similarly, human PARK7/DJ-1 mutant iPSC-derived microglia showed comparable transcriptional signatures, highlighting the translational relevance of our findings. These transcriptional alterations were also reflected mor-phologically, with microglia from LPS-treated PARK7/DJ-1 KO mice displaying a less amoeboid cell shape compared with wildtype mice. These observations suggest that the underlying oxidative stress arising from PARK7/DJ-1 deficiency impacts microglial activation states. As balanced immune responses are crucial for CNS homeostasis, compromised microglial responses under DJ-1 deficien-cy could contribute to PD development and progression.