We first made use of human primary fibroblasts derived from patients affected by Familial Dysautonomia (FD) (Figure 4A), a condition characterized by the loss of Elp1 expression (IKBKAP-/-) [34], a key component of the Elongator complex essential for the biosynthesis of mcm5s2U-modified tRNA (Figure 3B) [35]. Here, ELP1 is linked to Riley-Day syndrome.