TARDBP and Alzheimer disease: The serotonergic system is also implicated in AD (Trillo et al., 2013; Šimić et al., 2017) and some studies suggest that loss of serotonergic input is associated with early behavioral changes in AD, including increased agitation and loss of emotional regulation, clinical features that manifest before the later onset of memory loss and may also correlate with concomitant TDP-43 pathology (Sennik et al., 2017; Elferink et al., 2015; Simic et al., 2009).