A Dynamic Splicing Program Ensures Proper Synaptic Connections in the Developing Cerebellum

Tight coordination of gene expression in the developing cerebellum is crucial for establishment of neuronal circuits governing motor and cognitive function. However, transcriptional changes alone do not explain all of the switches underlying neuronal differentiation. Here we unveiled a widespread and highly dynamic splicing program that affects synaptic genes in cerebellar neurons. The motifs enriched in modulated exons implicated the splicing factor Sam68 as a regulator of this program. Sam68 controls splicing of exons with weak branchpoints by directly binding near the 3′ splice site and competing with U2AF recruitment. Ablation of Sam68 disrupts splicing regulation of synaptic genes associated with neurodevelopmental diseases and impairs synaptic connections and firing of Purkinje cells, resulting in motor coordination defects, ataxia, and abnormal social behavior. These findings uncover an unexpectedly dynamic splicing regulatory network that shapes the synapse in early life and establishes motor and cognitive circuitry in the developing cerebellum

A Dynamic Splicing Program Ensures Proper Synaptic Connections in the Developing Cerebellum

Tight coordination of gene expression in the developing cerebellum is crucial for establishment of neuronal circuits governing motor and cognitive function. However, transcriptional changes alone do not explain all of the switches underlying neuronal differentiation. Here we unveiled a widespread and highly dynamic splicing program that affects synaptic genes in cerebellar neurons. The motifs enriched in modulated exons implicated the splicing factor Sam68 as a regulator of this program. Sam68 controls splicing of exons with weak branchpoints by directly binding near the 3′ splice site and competing with U2AF recruitment. Ablation of Sam68 disrupts splicing regulation of synaptic genes associated with neurodevelopmental diseases and impairs synaptic connections and firing of Purkinje cells, resulting in motor coordination defects, ataxia, and abnormal social behavior. These findings uncover an unexpectedly dynamic splicing regulatory network that shapes the synapse in early life and establishes motor and cognitive circuitry in the developing cerebellum

Clinical variability at the mild end of BRAT1-related spectrum: Evidence from two families with genotype–phenotype discordance

Biallelic mutations in the BRAT1 gene, encoding BRCA1-associated ATM activator 1, result in variable phenotypes, from rigidity and multifocal seizure syndrome, lethal neonatal to neurodevelopmental disorder, and cerebellar atrophy with or without seizures, without obvious genotype-phenotype associations. We describe two families at the mildest end of the spectrum, differing in clinical presentation despite a common genotype at the BRAT1 locus. Two siblings displayed nonprogressive congenital ataxia and shrunken cerebellum on magnetic resonance imaging. A third unrelated patient showed normal neurodevelopment, adolescence-onset seizures, and ataxia, shrunken cerebellum, and ultrastructural abnormalities on skin biopsy, representing the mildest form of NEDCAS hitherto described. Exome sequencing identified the c.638dup and the novel c.1395G>A BRAT1 variants, the latter causing exon 10 skippings. The p53-MCL test revealed normal ATM kinase activity. Our findings broaden the allelic and clinical spectrum of BRAT1-related disease, which should be suspected in presence of nonprogressive cerebellar signs, even without a neurodevelopmental disorder

A novel piggybac transposon inducible expression system identifies a role for akt signalling in primordial germ cell migration

In this work, we describe a single piggyBac transposon system containing both a tet-activator and a doxycycline-inducible expression cassette. We demonstrate that a gene product can be conditionally expressed from the integrated transposon and a second gene can be simultaneously targeted by a short hairpin RNA contained within the transposon, both in vivo and in mammalian and avian cell lines. We applied this system to stably modify chicken primordial germ cell (PGC) lines in vitro and induce a reporter gene at specific developmental stages after injection of the transposon-modified germ cells into chicken embryos. We used this vector to express a constitutively-active AKT molecule during PGC migration to the forming gonad. We found that PGC migration was retarded and cells could not colonise the forming gonad. Correct levels of AKT activation are thus essential for germ cell migration during early embryonic development

Ror2 Enhances Polarity and Directional Migration of Primordial Germ Cells

The trafficking of primordial germ cells (PGCs) across multiple embryonic structures to the nascent gonads ensures the transmission of genetic information to the next generation through the gametes, yet our understanding of the mechanisms underlying PGC migration remains incomplete. Here we identify a role for the receptor tyrosine kinase-like protein Ror2 in PGC development. In a Ror2 mouse mutant we isolated in a genetic screen, PGC migration and survival are dysregulated, resulting in a diminished number of PGCs in the embryonic gonad. A similar phenotype in Wnt5a mutants suggests that Wnt5a acts as a ligand to Ror2 in PGCs, although we do not find evidence that WNT5A functions as a PGC chemoattractant. We show that cultured PGCs undergo polarization, elongation, and reorientation in response to the chemotactic factor SCF (secreted KitL), whereas Ror2 PGCs are deficient in these SCF-induced responses. In the embryo, migratory PGCs exhibit a similar elongated geometry, whereas their counterparts in Ror2 mutants are round. The protein distribution of ROR2 within PGCs is asymmetric, both in vitro and in vivo; however, this asymmetry is lost in Ror2 mutants. Together these results indicate that Ror2 acts autonomously to permit the polarized response of PGCs to KitL. We propose a model by which Wnt5a potentiates PGC chemotaxis toward secreted KitL by redistribution of Ror2 within the cell

Raccontare storie personali in classe. Dalla ricerca all'innovazione educativa

Il volume presenta i principali risultati di una ricerca svolta nell’ambito del progetto europeo SHARMED (Shared Memories and Dialogues), che ha riguardato la promozione di nuove esperienze di facilitazione della partecipazione degli studenti in classi multiculturali di scuole primarie e secondarie di primo grado, con un’attenzione particolare per la narrazione delle differenze culturali e la promozione del dialogo con gli studenti nell’interazione in classe, dialogo basato sulla promozione dell’equità, sull’empowerment e sul riconoscimento dei contributi dei bambini. I processi principali del progetto che vengono discussi nel volume sono: 1. La raccolta, l’utilizzo e l’archiviazione di materiali visuali, in particolare fotografie, riguardanti le memorie dei bambini e delle loro famiglie. 2. La produzione in classe delle narrazioni dei bambini riguardanti le loro memorie personali. 3. La facilitazione di descrizione, comparazione e condivisione di fotografie e storie attraverso una comunicazione dialogica. 4. La valutazione degli interventi da parte di bambini e insegnanti 5. Il progetto di formazione di insegnanti e facilitatori derivante dalla ricerca. Obiettivo generale del volume è spiegare come sono stati realizzati questi processi e con quali risultati nelle classi in cui è stato realizzato il progetto. Il volume evidenzia in particolare: 1. L’uso della fotografia e la competenza nel trattare e comparare materiali visuali relativamente alla memoria personale e culturale dei bambini. 2. La tipologia di narrazioni prodotte nelle classi a partire dalle fotografie. 3. L’applicazione di metodi di facilitazione all’uso di materiali visuali e alla produzione delle narrazioni. 4. L’analisi e la valutazione delle attività in classe riguardanti il significato (a) dei metodi di facilitazione e dell’uso dei materiali visuali, (b) della partecipazione dei bambini e delle loro narrazioni. 5. Il programma di formazione per gli insegnanti coinvolti, basato su un pacchetto che include anche un Massive Online Open Course (MOOC). I concetti chiave utilizzati e spiegati nel volume riguardano: l’uso sociale della fotografia, il significato sociale della memoria, la narrazione, la facilitazione della partecipazione e dell’agency, la gestione dei conflitti, la comunicazione interculturale nelle classi. Il progetto è stato realizzato in tre paesi (Germania, Italia e Regno Unito). Il volume presenta tuttavia i risultati conseguiti in Italia e nel Regno Unito. Il volume è basato su interventi di facilitazione in 32 classi scolastiche, per un totale di un centinaio di incontri in classe, sulle interviste alle insegnanti coinvolte e sulla combinazione tra un questionario di valutazione e un focus group rivolti ai bambini