We characterized the 3’ end sequence of the lncMN3 transcript using rapid amplification of cDNA ends (RACE) and we confirmed the existence of the annotated isoform (Appendix Fig. S1A).

The analysis of the expression profile of lncMN3 during mESCs in vitro differentiation to MNs indicated that while it is not expressed in mESCs, it starts to be present in embryoid bodies at day 5 (EB5), reaches its maximum in EBs at day 6 (EB6) and decreases in the mixed population containing MNs (DIV3) obtained after cells dissociation (Fig. 1B). The observed decrease in expression is probably caused by a dilution effect due to the experimental protocol used for MN differentiation (Wichterle and Peljto, 2008) rather than to a real down-regulation. In fact, the MN population obtained upon EBs dissociation accounts for 40% of the mixed neural cell population; moreover, in contrast to the mixed population which continues to divide, MNs are postmitotic cells and their amount is diluted as differentiation proceeds (Capauto et al, 2018).