The Role of Microglia in Neuronal ceroid lipofuscionosis

Neuronal ceroid lipofuscionosis (NCL) summarizes a group of human childhood neurodegenerative genetic disorders with occurrence between 1:12,500 and 1:100,000 depending on the genetic background of the population. The phenotypic characteristics of NCL patients include dementia, seizures, and visual loss as an early sign of onset of the disease. So far, 14 disease-causing genes and their genetic mutations are described, however their impact in the fundaments of molecular and cellular dynamics are not well-known. Although mouse models have provided important insights into the disease development from a neuro-centric view, they lack first, the immune-relevant perspective and second, a direct correlation to the human pathophysiology. In addition, several of NCL disease phenotypes could not be recapitulated in mice. In this proposal, we will study the fundaments of NCL from a novel angle, namely focusing on the impact of genetic mutations within the immune-responsive microglia. We have previously shown that microglia in the retina express a set of NCL disease genes exclusively. This is interesting because microglia have been associated with various neurodevelopmental and neurodegenerative diseases. Hence in our study, we will focus on developing human microglia harboring the disease-causing mutations and analyzing their function. For this, we will use a genome-editing strategy, which allows us to perform targeted mutation within the gene locus. We will induce the most frequent mutation into the genes of CLN1 to 3 in human induced pluripotent stem (iPS) cells. These iPS cells have the possibility to differentiate in any neuronal or glial cell type. We will differentiate the mutation-carrying and healthy control iPS cells into microglia. Then we will compare their intracellular alterations such as changes in the lysosomal activity as well as their interaction with the nervous system. The result of this study will provide important insights into the role of microglia in NCL and could offer a new strategy for cell targeted drug approaches.

The role of microglia in Neuronal ceroid lipofuscinosis Neuronal ceroid lipofuscinosis (NCLs) summarize a group of human childhood neurodegenerative genetic disorders with phenotypic characteristics like dementia, seizures, and visual loss. The disease occurrence is between 1:12,500 and 1:100,000 depending on the genetic background of the population. The project 'Role of microglia in neuronal ceroid lipofuscinosis' aimed to develop human cellular models for NCL to elucidate mechanisms underlying the disease development, with emphasis on microglia, the immune cells of the central nervous system, and their interaction with neurons. Microglia have been implicated in numerous neurodegenerative diseases. Their activation or dysfunction by various stimuli or mutations can induce pro-inflammatory effects, altering neuronal function and survival. New insights into NCL human pathological autopsies show that neuronal loss is highest where microglial activation is most pronounced, suggesting a close association of neurodegenerations with neuroimmune processes. Although NCL human autopsy material and mouse models have offered important insights into the disease development, they provide limited sample material and present limitations for a direct correlation to the human pathophysiology. Hence, it was crucial to develop in vitro cellular models that mimic human pathophysiology to address molecular and cellular dynamics. Our research project has established in vitro cell models for a juvenile form of NCL, the CLN3 disease. We have induced mutations into the CLN3 gene in human induced pluripotent stem (hiPS) cells using a genome-editing strategy to mimic the NCL disease in these cells. Since hiPS cells can differentiate into any cell type, we have established and successfully differentiated healthy and mutation-induced hiPS cells into neurons and microglia. Finally, we could study NCL disease in a Petri dish and understand it better. Our results will help us and other scientists to learn how nerve cells and immune cells in the brain talk to each other and methods and drugs to treat this disease. Further, we have established various functional assays such as phagocytosis, apoptosis, and cell proliferation to characterize neurons and microglia in wild type and mutant cell types. The potential impact of our outcomes is high as these models could help gain novel insights into the interplay of microglia and neurons during disease progression and offer a strategy for cell-targeted drug approaches. Finally, we could study NCL disease in a Petri dish and understand it better. Our results will help us and other scientists to learn how nerve cells and immune cells in the brain talk to each other and methods and drugs to treat this disease.