Printed Poster | Session 1

013 – Microglia distinct and disease associated protein signature in ALS.

Romina Barreto-Núñez (1) – Louis-Charles Béland (1) – Hejer Boutej (1) – Luis Barbeito (2) – Jasna Kriz (3)
Université Laval, Faculty of Medicine, Quebec, Canada (1) – Institut Pasteur de Montevideo, Neurodegeneration Lab, Montevideo, Uruguay (2) – Université Laval, Department of Psychiatry and Neuroscience, Faculty of Medicine,, Quebec, Canada (3)

Microglial cells are the principal immune cells of the brain and main effectors of innate immune response after injuries and in chronic neurodegeneration. However, their role in chronic neurodegenerative disorders is complex. Initially beneficial, over the course of disease microglial cells acquire reactive and highly toxic phenotypes. One of our recent studies suggests that a shift from beneficial to detrimental cellular phenotypes, in the SOD1G93A ALS mouse model, coincides with a loss of capacity of microglia to maintain immune homeostasis. We hypothesized that the appearance of neurotoxic microglia phenotype in ALS is the consequence of the disease-induced de-differentiation of microglia into aberrant cells leading to a loss of normal immune function thus contributing to disease progression.

While recent studies uncovered several disease associated changes in microglia at gene/RNA level, the actual cell specific signature at protein level remains elusive. Our research aims to study and identify the cell specific molecular signature of aberrant microglia at protein level that appears exclusively in the symptomatic phase of disease in SOD1G93A mouse model.

To assess cell specific changes in microglia at protein level in vitro and in vivo we took advantage of a double transgenic mouse model CD11prom-Flag/EGFP-RPL10a;SOD1G93A recently developed in our lab. First, we isolated and characterized the aberrant microglial cells from the spinal cord of symptomatic animals in vitro. Second, we performed the modified Translating Ribosome Affinity Purification (TRAP) methodology for the isolation of the stabilized polysome complexes together with attached peptides. Microglia proteome/peptides will be analyzed by label free high sensitivity mass spectrometry (LC-MS/MS).

We isolated and characterized the aberrant microglial cells from the spinal cord of symptomatic animals. These cells appeared exclusively in the symptomatic phase and shown a disease associated profile. We identified a distinct, disease associated protein signature in chronically activated ALS microglia. Functionally, aberrant microglial cells showed a marked deregulation of innate immune response and phagocytic activity. Together our results provide the first comprehensive analysis of disease associated microglia proteome. Further research is needed to better understand how the observed disease-associated shift in microglia protein expression contributes to disease progression.