ABSTRACT
FTSJ1 is a conserved human 2’-O-methyltransferase (Nm-MTase) that modifies several transfer RNAs (tRNAs) at position 32 and the wobble position 34 in the AntiCodon Loop (ACL). Its loss of function has been linked to Non-Syndromic X-Linked Intellectual Disability (NSXLID), and more recently to cancers. However, the molecular mechanisms underlying these pathologies are currently unclear. Here we report a novel FTSJ1 pathogenic variant from a NSXLID patient. Using blood cells derived from this patient and other affected individuals carrying FTSJ1 mutations, we performed an unbiased and comprehensive RiboMethSeq analysis to map the ribose methylation (Nm) on all human tRNAs and identify novel targets. In addition, we performed a transcriptome analysis in these cells and found that several genes previously associated with intellectual disability and cancers were deregulated. We also found changes in the miRNA population that suggest potential cross-regulation of some miRNAs with these key mRNA targets. Finally, we show that differentiation of FTSJ1-depleted human neuronal progenitor cells (NPC) into neurons displays long and thin spine neurites compared to control cells. These defects are also observed in Drosophila and are associated with long term memory deficit in this organism. Altogether, our study adds insight into FTSJ1 pathologies in human and flies by the identification of novel FTSJ1 targets and the defect in neuron morphology.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
● We identify eight novel human FTSJ1 tRNA targets using an unbiased and innovative mapping approach (RiboMethSeq) as well as confirm the previously identified ones. As requested, Table 2 now includes extended referencing in 4 different organisms (Human, Mice, D. melanogaster and S. Cerevisiae). Corresponding details and explanations are now depicted in the adapted section (Results, Material and Methods and Discussion). The new data is shown as new Figure 1 and Table 2. ● We demonstrate for the first time in human cells, that the loss of FTSJ1 in immature neurons (from progenitor cells (NPC) KD for FTSJ1) affects neurogenesis. Furthermore we found that this phenotype is conserved in D. melanogaster and is importantly associated with long term memory (LTM) defects, due to either Nm34 or Nm32 loss on tRNAs. As requested by the 3 Reviewers, two additional genotypes were included, and importantly we show that both ACL modifications are involved in LTM and not in short term memory (STM). The new data is shown as new Figure 6. ● We performed OE and KD experiments of miR-181a-5p, and show that miR-181a-5p is targeting the BTBD3 transcripts, whose product is known to direct the dendritic field orientation during development of the sensory neuron in mice cortex. Strikingly, this silencing is affected in FTJS1 mutated cells giving rise to a deregulation of BTBD3 level. This result, shown here in human cells, is in line with the neuronal morphology observed in human NPC (Figure 4) and flies NMJ (Figure 5), as well as with previously reported data on mice (Nagayoshi et al. 2021). The new data is shown as new Supplemental Figure S4. ● The requested changes for Figure 1, Table 2 and Figure 2A are now embedded in new Figure 1, Table 2 and Figure 2A. ● D. Dimitrova and M. Brazane are co-first authors
