GAP43 and Alzheimer disease: Neuronal degeneration and loss are pathological hallmarks of ALS and AD,[22, 23] whereas GAP43 promotes neuronal growth and repair.[24] In this study, we found that GAP43 mRNA was significantly downregulated following TDP‐43 depletion in cortical neurons capable of differentiation, as well as in AD brains with pathological pTDP‐43.