MOLECULAR PROFILING OF MICROGLIA-ASTROCYTE CROSSTALK IN C9ORF72 ALS/FTD REVEALS DYSREGULATION OF CRITICAL SIGNALING PATHWAYS

Amyotrophic Lateral Sclerosis (ALS) is a neurodegenerative disease characterized by the loss of motor neurons, and frontotemporal dementia (FTD) is a dementia syndrome caused by the degeneration of the frontal and temporal lobes. The most common genetic cause of both these diseases is the C9orf72 hexanucleotide repeat expansion (HRE). Much of the knowledge in C9orf72-ALS/FTD disease pathogenesis has come through investigations of neuronal disease mechanisms with little focused on glial cells or glia-glia cell interaction.
To investigate this knowledge gap, I utilized human C9orf72 patient derived induced pluripotent stem cells (iPSCs) differentiated into microglia and cortical astrocytes. I evaluated cell and non-cell autonomous functions of microglia and astrocytes by analyzing their secreted factors, and exposing them to the opposite glia-conditioned media. A glia crosstalk molecular profile has been generated using transcriptomic, proteomic, and multiplexed ELISA analysis.
Our results indicate greater responsiveness of microglia to astrocytic signals when compared to astrocytes provided microglial signals. Microglia appear to upregulate a signaling pathway involving THBS1-VEGF-PKC which can lead to a reduction in the critical antioxidant mRNA glutamate-cystine ligase catalytic subunit (GCLC). In astrocytes, we identified an increase in protein of a previously identified ALS susceptibility gene, zeta crystallin (CRYZ) which is predicted to interact with the KEAP1-NRF2 oxidative stress pathway. Additionally, we observed an increase in a kinesin superfamily protein, KIF13A, which is a critical component of the golgi-plasma membrane endosomal pathway.
Together, these data provide a framework for identifying novel biomarkers and therapeutic targets arising from dysregulated microglia–astrocyte crosstalk in ALS/FTD.