TAFA5 and early-onset autosomal dominant Alzheimer disease: Understanding the function of FAM19A5 in the brain is of particular importance because recent clinical studies have revealed the genetic association of FAM19A5 with brain development-related symptoms, such as ADHD and autism (Kashevarova et al., 2018), and degenerative disease, such as Alzheimer disease (Herold et al., 2016; Mez et al., 2017).