TSEN54 and pontocerebellar hypoplasia: Morpholino knockdown of endogenous rars2 in zebrafish leads to underdevelopment and structural abnormalities within the brain, mirroring morphological defects induced by knockdown of the tsen54 gene that encodes tRNA-splicing endonuclease complex, which like RARS2, has been linked to pontocerebellar hypoplasia (PCH) in human patients (Kasher et al., 2011).