Deleting TREM2 exacerbated tau accumulation and spreading, and promoted brain atrophy only if Aβ pathology is present, indicating that TREM2 may slow AD progression and reduce tau-driven neurodegeneration by restricting the degree to which Aβ facilitates the spreading of pathogenic tau (Lee et al. 2021). The gene discussed is TREM2; the disease is Alzheimer disease.