A replicated astrocyte long non-coding RNA signature of Alzheimer's disease is inverted in amyotrophic lateral sclerosis.
Reactive astrocyte transitions are central to neurological disease, yet their long non-coding RNA (lncRNA) regulators remain poorly defined, and single-nucleus studies frequently treat nuclei rather than donors as replicates. This study analyses publicly available human single-nucleus RNA sequencing from four disorders using donors as the unit of inference throughout: Alzheimer's disease (AD; middle temporal gyrus, 88 donors), C9orf72-associated amyotrophic lateral sclerosis and ALS/frontotemporal dementia (ALS; frontal cortex), multiple sclerosis (MS; cortex and white matter), and major depressive disorder (MDD; amygdala). The public MDD release pools nuclei by condition, so that arm cannot support donor-level inference and is exploratory only. Covariate-adjusted pseudobulk analysis of 70,009 CE astrocytes, controlling for sex, age at death and assay chemistry, identified 1,019 down-regulated autosomal lncRNAs after sex-chromosome transcripts were removed. This signature was not attributable to astrocyte subtype composition, which did not differ between groups, and 99.9% of members remained down-regulated within the dominant homeostatic subtype alone. The signature replicated in an independent AD cohort (32 of 41 testable members concordant; resampling P < 0.0001). Testing it outside AD gave a directional result: it was concordant in the MS discovery cohort (P < 0.0001) but inconclusive in an independent MS cohort in which the transcripts lay near the detection floor, and it was reproducibly inverted in ALS, in the C9orf72 discovery cohort and in an independent motor-cortex cohort not restricted to C9orf72 carriers. The inversion survived negative controls for global normalisation and expression level. These astrocyte lncRNA changes are therefore disorder-specific rather than pan-neuroinflammatory.