Expression of ALS-PFN1 impairs vesicular degradation in iPSC-derived microglia

Abstract

Microglia play a pivotal role in neurodegenerative disease pathogenesis, but the mechanisms underlying microglia dysfunction and toxicity remain to be fully elucidated. To investigate the effect of neurodegenerative disease-linked genes on the intrinsic properties of microglia, we studied microglia-like cells derived from human induced pluripotent stem cells (iPSCs), termed iMGs, harboring mutations in profilin-1 (PFN1) that are causative for amyotrophic lateral sclerosis (ALS). ALS-PFN1 iMGs exhibited lipid dysmetabolism and deficits in phagocytosis, a critical microglia function. Our cumulative data implicate an effect of ALS-linked PFN1 on the autophagy pathway, including enhanced binding of mutant PFN1 to the autophagy signaling molecule PI3P, as an underlying cause of defective phagocytosis in ALS-PFN1 iMGs. Indeed, phagocytic processing was restored in ALS-PFN1 iMGs with Rapamycin, an inducer of autophagic flux. These outcomes demonstrate the utility of iMGs for neurodegenerative disease research and highlight microglia vesicular degradation pathways as potential therapeutic targets for these disorders.

Recent insights from human induced pluripotent stem cell models into the role of microglia in amyotrophic lateral sclerosis

“…Introducing ALS‐associated mutations ( C71G, M114T ) in profilin‐1 ( PFN1 ) to iPSC microglia caused significant proteomic and transcriptomic dysregulation associated with microglial lipid metabolism and vesicular degradation. [ 3 ] Interestingly, LPS stimulation produced no difference in cytokine release of IL6, IL10, CCL5, and TNF‐α between PFN1 mutant and wildtype microglia after 6 and 24‐h, suggesting PFN1 is not involved in microglial inflammation. Instead, PFN1 mutants exhibited increased pHrodo bioparticle signal upon phagocytic uptake.…”

“…Impairments in autophagy and lysosomal degradation were found in C9orf72 and PFN1 mutant microglia. [3,6] There is evidence for changes in phagocytosis, [3,6] but it remains unclear whether phagocytosis is decreased or increased and whether this is a true effect or due to impairments in the autophagy-lysosome pathway. Increased calcium signaling was found in FUS mutant microglia.…”

“…Some ALS‐associated genes are highly expressed in microglia, including C9orf72 , FUS, PFN1, OPTN , and TBK1 , suggesting that mutations in these genes could have ALS‐relevant effects on microglial biology. [ 1–3 ] Indeed, an activated microglial state has been described in animal models and human post‐mortem studies, suggesting microglia have an early anti‐inflammatory effect during in ALS, followed by a late proinflammatory phenotype (reviewed in more detail in ref. [1]).…”

“…There is notable overlap with the related condition frontotemporal dementia (FTD), with microglial biology. [1][2][3] Indeed, an activated microglial state has been described in animal models and human post-mortem studies, suggesting microglia have an early anti-inflammatory effect during in ALS, followed by a late proinflammatory phenotype (reviewed in more detail in ref. [1]).…”

Development of a high-throughput, quantitative platform using human cerebral organoids to study virus-induced neuroinflammation in Alzheimer’s disease

“…Given these exciting prior discoveries, we sought to identify molecular and cellular biomarkers to develop high-throughput, quantitative assays around the use of human cerebral organoids, specifically for virus-induced neuroinflammation in AD. Microglia, the resident immune cells in the central nervous system, are differentiated from the mesodermal lineage in-vitro 45,46 . As such, it was widely thought that cerebral organoids did not contain microglia and would not produce interferon response upon viral infection.…”