Also, expression of SLC6A5, encoding the glycine transporter 2 (GLYT2), is located to presynaptic elements of glycinergic neurons in brain stem (Zafra et al., 1995) and its expression was reduced in HEL100.2 NPCs at D7 compared with other FXS NPCs (Figure 5D). Here, SLC6A5 is linked to fragile X syndrome.