Hypoxic stress is an early pathogenic event in human VCP-mutant ALS astrocytes.

Astrocytes are essential regulators of neuronal health, and their dysfunction contributes to neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS). Using human induced pluripotent stem cell (iPSC)-derived astrocytes carrying ALS-associated VCP mutations, we uncover cell-autonomous activation of the hypoxia response under basal conditions. VCP-mutant astrocytes exhibit increased nuclear hypoxia-inducible factor (HIF)-1ɑ, mitochondrial depolarization, and lipid droplet accumulation. Mimicking hypoxia in control astrocytes by HIF-1ɑ stabilization with dimethyloxalylglycine recapitulates these phenotypes. Transcriptomic and CUT&RUN profiling reveal direct HIF-1ɑ binding to canonical hypoxia-responsive genes in VCP-mutant astrocytes and a transcriptional signature of metabolic reprogramming and mitochondrial dysfunction under normoxia. Furthermore, conditioned medium from hypoxia-exposed astrocytes fails to rescue RNA-binding protein mislocalization in motor neurons, unlike medium from healthy counterparts. Together, these findings demonstrate that aberrant HIF-1ɑ activation drives astrocytic dysfunction and compromises neuronal support, identifying hypoxic stress as an early and functionally consequential event in VCP-mutant ALS, with therapeutic implications for targeting HIF-1ɑ signaling.