In our case, expression in the retina led to an unexpected discovery that Tom40 overexpression drives retinal neurodegeneration, providing insight into a strong risk factor in Alzheimer’s disease afforded by intronic ′523 TOMM40 variants that exhibit comparable levels of increased TOMM40 expression (Roses et al., 2010 ▸). Here, TOMM40 is linked to early-onset autosomal dominant Alzheimer disease.