MAPT and early-onset autosomal dominant Alzheimer disease: Recent studies have implicated dysregulated piRNA pathways in neurodevelopmental and neurodegenerative disorders, such as Alzheimer's disease,[40, 41] Parkinson's disease,[42, 43] and autism spectrum disorders.[44] For instance, altered piRNA expression profiles have been observed in brain tissues of patients with Alzheimer's disease, potentially contributing to aberrant tau phosphorylation and amyloid‐β accumulation through interactions with synaptic plasticity‐related genes.