Transmembrane and coiled‐coil 2 (TMCC2) forms an evolutionarily conserved complex with the amyloid protein precursor (APP) [1, 2], the source of the Aβ peptide whose accumulation as amyloid plaques in the brain defines Alzheimer's disease (AD). The gene discussed is TMCC2; the disease is early-onset autosomal dominant Alzheimer disease.