SLC4A4 and obesity due to melanocortin 4 receptor deficiency: The mEC1 population showed an obesity-induced downregulation of transporters of major ions (Slc34a1, Slc4a4, Slc22a8, Slc13a1, Slc22a18 and Slc5a12), neutral amino acids (Slc6a19) and glucose (Slc5a2; Extended Data Fig. 7i).