Moreover, OSN-specific expression of the Swedish mutated form of the human APP gene disrupted the precise projections of their axons to the OB during synapse formation in 3-month-old Tg2576 mice without OSN death.20 Therefore, it is possible that abnormal axonal projections of OSNs are involved in the earlier olfactory dysfunction and in turn induce the cell death of OSNs with aberrant projections, resulting in more severe dysfunction in the early stage of AD. The gene discussed is APP; the disease is Alzheimer disease.