Specification of spinal cord neurons depends on gene regulation networks that impose distinct fates in neural progenitor cells (NPCs).Olig2 is a key transcription factor in these networks by inducing motor neuron (MN) specification and inhibiting interneuron identity. Despite the critical role of Olig2 in nervous system development and cancer progression, the upstream molecular mechanisms that control

Exploration of non-coding genome has recently uncovered a growing list of formerly unknown regulatory long non-coding RNAs (lncRNAs) with important functions in stem cell pluripotency, development and homeostasis of several tissues. Although thousands of lncRNAs are expressed in mammalian brain in a highly patterned manner, their roles in brain development have just begun to emerge. Recent data suggest key roles for these molecules in gene regulatory networks controlling neuronal and glial cell differentiation. Analysis of the genomic distribution of genes encoding for lncRNAs indicates a physical association of these regulatory RNAs with transcription factors (TFs) with well-established roles in neural differentiation, suggesting that lncRNAs and TFs may form coherent regulatory networks with important functions in neural stem cells (NSCs). Additionally, many studies show that lncRNAs are involved in the pathophysiology of brain-related diseases/disorders. Here we discuss these observations and investigate the links between lncRNAs, brain development and brain-related diseases. Understanding the functions of lncRNAs in NSCs and brain organogenesis could revolutionize the basic principles of developmental biology and neuroscience.

Background Sarcopenia, the age-associated decline in skeletal muscle mass and strength, has long been considered a disease of muscle only, but accumulating evidence suggests that sarcopenia could originate from the neural components controlling muscles. To identify early molecular changes in nerves that may drive sarcopenia initiation, we performed a longitudinal transcriptomic analysis of the sciatic nerve, which governs lower limb muscles, in aging mice. Methods Sciatic nerve and gastrocnemius muscle were obtained from female C57BL/6JN mice aged 5, 18, 21 and 24 months old (n = 6 per age group). Sciatic nerve RNA was extracted and underwent RNA sequencing (RNA-seq). Differentially expressed genes (DEGs) were validated using quantitative reverse transcription PCR (qRT-PCR). Functional enrichment analysis of clusters of genes associated with patterns of gene expression across age groups (adjusted P-value < 0.05, likelihood ratio test [LRT]) was performed. Pathological skeletal muscle aging was confirmed between 21 and 24 months by a combination of molecular and pathological biomarkers. Myofiber denervation was confirmed with qRT-PCR of Chrnd, Chrng, Myog, Runx1 and Gadd45ɑ in gastrocnemius muscle. Changes in muscle mass, cross-sectional myofiber size and percentage of fibres with centralized nuclei were analysed in a separate cohort of mice from the same colony (n = 4-6 per age group). ResultsWe detected 51 significant DEGs in sciatic nerve of 18-month-old mice compared with 5-month-old mice (absolute value of fold change > 2; false discovery rate [FDR] < 0.05). Up-regulated DEGs included Dbp (log 2 fold change [LFC] = 2.63, FDR < 0.001) and Lmod2 (LFC = 7.52, FDR = 0.001). Down-regulated DEGs included Cdh6 (LFC = À21.38, FDR < 0.001) and Gbp1 (LFC = À21.78, FDR < 0.001). We validated RNA-seq findings with qRT-PCR of various up-and down-regulated genes including Dbp and Cdh6. Up-regulated genes (FDR < 0.1) were associated with the AMP-activated protein kinase signalling pathway (FDR = 0.02) and circadian rhythm (FDR = 0.02), whereas down-regulated DEGs were associated with biosynthesis and metabolic pathways (FDR < 0.05). We identified seven significant clusters of genes (FDR < 0.05, LRT) with similar expression patterns across groups. Functional enrichment analysis of these clusters revealed biological processes that may be implicated in age-related changes in skeletal muscles and/or sarcopenia initiation including extracellular matrix organization and an immune response (FDR < 0.05). Conclusions Gene expression changes in mouse peripheral nerve were detected prior to disturbances in myofiber innervation and sarcopenia onset. These early molecular changes we report shed a new light on biological processes that may be implicated in sarcopenia initiation and pathogenesis. Future studies are warranted to confirm the disease modifying and/or biomarker potential of the key changes we report here.

BackgroundSarcopenia, the age-associated decline in skeletal muscle mass and strength, has long been considered a disease of muscle only, but accumulating evidence suggests that sarcopenia could originate from the neural components controlling muscles. To identify early molecular changes in the efferent nerves that may drive sarcopenia initiation, we performed a longitudinal transcriptomic analysis of the sciatic nerve in aging mice.MethodsSciatic nerve and gastrocnemius muscle were obtained from young adult, middleaged, old, and sarcopenic (5,18, 21 and 24 months old, respectively) C57BL/6J female mice (n=6 per age group). Sciatic nerve RNA was extracted and subjected to RNA sequencing (RNA-seq), with real-time quantitative reverse transcription PCR (qRT-PCR) validation of differentially expressed genes (DEGs). Functional enrichment analysis of clusters of genes associated with patterns of gene expression across age groups was performed. Sarcopenia was confirmed with qRT-PCR of previously established markers of sarcopenia onset in gastrocnemius muscle.ResultsWe detected 33 significant DEGs in sciatic nerve of 18-month-old mice compared to 5-month-old mice (absolute value of fold change > 2; false discovery rate [FDR] < 0.05) which we validated with qRT-PCR of the three top up- and down-regulated genes. Up-regulated genes were associated with circadian rhythm and the AMPK signaling pathway, while down-regulated genes were associated with biosynthesis and metabolic pathways and circadian rhythm. Strikingly, we detected a significant increase in Myog expression (log2 fold change = 18.93, FDR q-value = 1.54×10−12) in sciatic nerve of 18-month-old mice, before up-regulation in muscle was observed. We identified seven clusters of genes with similar expression patterns across groups. Functional enrichment analysis of these clusters revealed biological processes that may be implicated in sarcopenia initiation including extracellular matrix organization and circadian regulation of gene expression.ConclusionsGene expression changes in mouse peripheral nerve can be detected prior to overt clinical onset of sarcopenia. These early molecular changes we report shed a new light on biological processes that may be implicated in sarcopenia initiation and pathogenesis. Future studies will validate which of the key changes we reported have disease modifying and/or biomarker potential.

Τα κυτταρικά συστήματα αποικοδόμησης πρωτεϊνών επηρεάζουν ουσιαστικά τα σηματοδοτικά μονοπάτια και μοριακά δίκτυα που ρυθμίζουν την οργανογένεση. Παρ'όλο που η αποικοδόμηση πρωτεϊνών μέσω αυτοφαγίας έχει συσχετιστεί πολύ ισχυρά με τη λειτουργία του εγκεφάλου και σχετικές ασθένειες, η συμμετοχή αυτής στην ανάπτυξη του νευρικού συστήματος παραμένει ασαφής. Η Αυτοφαγία Διαμεσολαβούμενη απο Σαπερόνες, ένα από τα κύρια λυσοσωμικά μονοπάτια, έχει συνδεθεί άμεσα με νευροεκφυλιστικές ασθένειες και ασθένειες σχετικές με την ανάπτυξη του εγκεφάλου, παρ' όλ' αυτά δεν υπάρχει κάτι γνωστό σχετικά με το φυσιολογικό ρόλο αυτής στην ανάπτυξη του εγκεφάλου των θηλαστικών. Με αυτή την εργασία παρουσιάζουμε ένα καινοτόμο ρυθμιστικό ρόλο της Αυτοφαγίας Διαμεσολαβούμενης απο Σαπερόνες, κατά τη διαφοροποίηση των Νευρικών Βλαστικών κυττάρων (ΝΒΚ) κατά τη διάρκεια της ανάπτυξης. Συγκεκριμένα, παρουσιάζουμε πως αυτό το μονοπάτι αυτοφαγίας είναι σημαντικά ενεργό στα ΝΒΚ και πως η LAMP2A, η βασικότερη πρωτεΐνη του μονοπατιού, μαζί με την HSC70 (HSPA8), ένα επιπλέον κομβικό μόριο για αυτό το αυτοφαγικό μονοπάτι, εκφράζονται σημαντικά και στα ΝΒΚ και στο εμβρυονικό εγκέφαλο των τρωκτικών. Επιπλέον, η LAMP2A συσχετίζεται με την έναρξη της νευρογένεσης. Πιο σημαντικά ακόμα, παρατηρείται πως υπερέκφραση και αποσιώπηση της LAMP2A οδηγεί στην ενεργοποίηση της νευρογένεσης κατά την διαφοροποίηση των ΝΒΚ. Σχετικά με τον μηχανισμό, στην μελέτη αυτή παρουσιάζεται πως η LAMP2A επηρεάζει την κυτταρική διαφοροποίηση των ΝΒΚ παρεμβαίνοντας στο NOTCH1 σηματοδοτικό μονοπάτι. Η υπερέκφραση της LAMP2A καταστέλλει την έκφραση του NICD (του ενδοκυτταρικού τμήματος της NOTH1 πρωτεΐνης που λειτουργεί ως μεταγραφικός παράγοντας στον πυρήνα) όπως επίσης και την έκφραση των γονιδίων που επάγει το NICD, το HES5 και HES1. Επιπρόσθετα, το γνωστό και αναγνωρίσιμο μοτίβο των πρωτεϊνών-στόχων στην αμινοξική τους αλληλουχία( KFERQ-like motif) της Αυτοφαγίας Διαμεσολαβούμενης απο Σαπερόνες , αναγνωρίστηκε στο NICD και φαίνεται να καθορίζει την ενεργότητά του σχετικά με την μεταγραφή των γονιδίων-στόχων. Η ρύθμιση αυτή φαίνεται να συμβαίνει μέσω της αποικοδόμησης της πρωτεΐνης NICD από το μονοπάτι της Αυτοφαγίας . Εν κατακλείδι, τα δεδομένα που προκύπτουν από την παρούσα εργασία οδηγούν στο συμπέρασμα ενός νέου ουσιαστικού ρόλου της LAMP2A και της Αυτοφαγίας Διαμεσολαβούμενης απο Σαπερόνες στην ρύθμιση της νευρονικής μοίρας του κυττάρου μέσω στόχευσης του NICD, επομένως και της ενεργότητας του NOTCH1 σηματοδοτικού μονοπατιού.