The human TRM82 ortholog WDR4 was associated with reduced tRNA m7G modification and a distinct form of microcephalic primordial dwarfism [29]; METTL1 or WDR4 knock out mouse embryonic stem cells showed defects in self renewal and differentiation [46]; and METTL1 was also responsible for m7G modification of mammalian miRNAs and mRNAs [55,56]. Here, WDR4 is linked to isolated growth hormone deficiency type IA.