SLC6A19 and Hartnup disease: In conclusion, the neutral amino acid transporter B0AT1, with Hartnup disease-associated mutations, has been experimentally shown to exhibit ER retention, suggesting the involvement of ERAD pathway in its pathogenesis (Christianson et al., 2011; Gariballa and Ali, 2020; Gariballa et al., 2024; Meusser et al., 2005; Qi et al., 2017; Tepedelen et al., 2019; Zacchi et al., 2022).