The mammalian nervous system is made up of an extraordinary array of diverse cells that form intricate functional connections. The programs underlying cell lineage specification, identity and function of the neuronal subtypes are managed by regulatory proteins and RNAs, which coordinate the succession of steps in a stereotyped temporal order. In the central nervous system (CNS), motor neurons (MNs) are responsible for controlling essential functions such as movement, breathing, and swallowing by integrating signal transmission from the cortex, brainstem, and spinal cord (SC) towards peripheral muscles. A prime role in guiding the progression of progenitor cells towards the MN fate has been largely attributed to protein factors. More recently, the relevance of a class of regulatory RNAs abundantly expressed in the CNS - the long noncoding RNAs (lncRNAs) - has emerged overwhelmingly. LncRNA-driven gene expression control is key to regulating any step of MN differentiation and function, and its derangement profoundly impacts neuronal pathophysiology. Here, we uncover a novel function for the neuronal isoform of HOTAIRM1 (nHOTAIRM1), a lncRNA specifically expressed in the SC. Using a model system that recapitulates spinal MN (spMN) differentiation, we show that nHOTAIRM1 intervenes in the binary cell fate decision between MNs and interneurons, acting as a pro-MN factor. Furthermore, human iPSC-derived spMNs without nHOTAIRM1 display altered neurite outgrowth, with a significant reduction of both branch and junction numbers. Finally, the expression of genes essential for synaptic connectivity and neurotransmission is also profoundly impaired when nHOTAIRM1 is absent in spMNs. Mechanistically, nHOTAIRM1 establishes both direct and indirect interactions with a number of target genes in the cytoplasm, being a novel post-transcriptional regulator of MN biology. Overall, our results indicate that the lncRNA nHOTAIRM1 is essential for the specification of MN identity and the acquisition of proper morphology and synaptic activity of post-mitotic MNs.

The impact of protein-coding genes on cancer onset and progression is a well-establishedparadigm in molecular oncology. Nevertheless, unveiling the contribution of the noncoding genes--including long noncoding RNAs (lncRNAs)--to tumorigenesis represents a great challenge forpersonalized medicine, since they (i) constitute the majority of the human genome, (ii) are essentialand flexible regulators of gene expression and (iii) present all types of genomic alterations describedfor protein-coding genes. LncRNAs have been increasingly associated with cancer, their highlytissue- and cancer type-specific expression making them attractive candidates as both biomarkersand therapeutic targets. Medulloblastoma is one of the most common malignant pediatric braintumors. Group 3 is the most aggressive subgroup, showing the highest rate of metastasis at diagnosis.Transcriptomics and reverse genetics approaches were combined to identify lncRNAs implicatedin Group 3 Medulloblastoma biology. Here we present the first collection of lncRNAs dependenton the activity of the MYC oncogene, the major driver gene of Group 3 Medulloblastoma. Weassessed the expression profile of selected lncRNAs in Group 3 primary tumors and functionallycharacterized these species. Overall, our data demonstrate the direct involvement of three lncRNAsin Medulloblastoma cancer cell phenotypes The impact of protein-coding genes on cancer onset and progression is a well-established paradigm in molecular oncology. Nevertheless, unveiling the contribution of the noncoding genes--including long noncoding RNAs (lncRNAs)--to tumorigenesis represents a great challenge for personalized medicine, since they (i) constitute the majority of the human genome, (ii) are essential and flexible regulators of gene expression and (iii) present all types of genomic alterations described for protein-coding genes. LncRNAs have been increasingly associated with cancer, their highly tissue- and cancer type-specific expression making them attractive candidates as both bi-omarkers and therapeutic targets. Medulloblastoma is one of the most common malignant pediatric brain tumors. Group 3 is the most aggressive subgroup, showing the highest rate of metastasis at diagnosis. Transcriptomics and reverse genetics approaches were combined to identify lncRNAs implicated in Group 3 Medulloblastoma biology. Here we present the first collection of lncRNAs dependent on the activity of the MYC oncogene, the major driver gene of Group 3 Medulloblastoma. We assessed the expression profile of selected lncRNAs in Group 3 primary tumors and functionally characterized these species. Overall, our data demonstrate the direct involvement of three lncRNAs in Medulloblastoma cancer cell phenotypes.