SUMMARYMulti-lineage neuronal, astrocytic and oligodendrocytic potential is considered a neural stem cell (NSC) trait. However, hippocampal NSCs generate neurons and astrocytes but not oligodendrocytes in vivo and how this is regulated is unknown. Here we show that the RNAseIII Drosha is an intrinsic regulator of stem cell maintenance and differentiation in the adult mouse hippocampus. Inactivation of Drosha results in exhaustion of the NSC pool, premature arrest of neurogenesis, and induction of oligodendrocyte fate commitment. Drosha silences Nuclear Factor IB (NFIB) in hippocampal NSCs by targeting a double-stranded hairpin in the NFIB mRNA, thereby repressing its expression in a Dicer and miRNA-independent manner. We show that NFIB is required and sufficient for oligodendrocyte fate and knockdown of NFIB rescues neurogenesis by Drosha-deficient hippocampal NSCs. Our findings reveal a novel mechanism for stem cell maintenance and oligodendrocyte fate restriction in the adult hippocampus.3

Olfactory receptors (ORs) and down-stream functional signaling molecules adenylyl cyclase 3 (AC3), olfactory G protein α subunit (Gαolf), OR transporters receptor transporter proteins 1 and 2 (RTP1 and RTP2), receptor expression enhancing protein 1 (REEP1), and UDP-glucuronosyltransferases (UGTs) are expressed in neurons of the human and murine central nervous system (CNS). In vitro studies have shown that these receptors react to external stimuli and therefore are equipped to be functional. However, ORs are not directly related to the detection of odors. Several molecules delivered from the blood, cerebrospinal fluid, neighboring local neurons and glial cells, distant cells through the extracellular space, and the cells’ own self-regulating internal homeostasis can be postulated as possible ligands. Moreover, a single neuron outside the olfactory epithelium expresses more than one receptor, and the mechanism of transcriptional regulation may be different in olfactory epithelia and brain neurons. OR gene expression is altered in several neurodegenerative diseases including Parkinson’s disease (PD), Alzheimer’s disease (AD), progressive supranuclear palsy (PSP) and sporadic Creutzfeldt-Jakob disease (sCJD) subtypes MM1 and VV2 with disease-, region- and subtype-specific patterns. Altered gene expression is also observed in the prefrontal cortex in schizophrenia with a major but not total influence of chlorpromazine treatment. Preliminary parallel observations have also shown the presence of taste receptors (TASRs), mainly of the bitter taste family, in the mammalian brain, whose function is not related to taste. TASRs in brain are also abnormally regulated in neurodegenerative diseases. These seminal observations point to the need for further studies on ORs and TASRs chemoreceptors in the mammalian brain.

Huntington disease (HD) is a neurodegenerative disorder caused by a CAG repeat expansion in the gene coding for huntingtin protein.Several mechanisms have been proposed by which mutant huntingtin (mHtt) may trigger striatal neurodegeneration, including mitochondrial dysfunction, oxidative stress, and apoptosis. Furthermore, mHtt induces DNA damage and activates a stress response. In this context, p53 plays a crucial role in mediating mHtt toxic effects. Here we have dissected the pathway of p53 activation by mHtt in human neuronal cells and in HD mice, with the aim of highlighting critical nodes that may be pharmacologically manipulated for therapeutic intervention. We demonstrate that expression of mHtt causes increased phosphorylation of p53 on Ser46, leading to its interaction with phosphorylation-dependent prolyl isomerase Pin1 and consequent dissociation from the apoptosis inhibitor iASPP, thereby inducing the expression of apoptotic target genes. Inhibition of Ser46 phosphorylation by targeting homeodomain-interacting protein kinase 2 (HIPK2), PKCδ, or ataxia telangiectasia mutated kinase, as well as inhibition of the prolyl isomerase Pin1, prevents mHttdependent apoptosis of neuronal cells. These results provide a rationale for the use of small-molecule inhibitors of stress-responsive protein kinases and Pin1 as a potential therapeutic strategy for HD treatment.

Dagmar iber 3,4 , christian Beisel 5 , erik van nimwegen 2 & Verdon taylor 1* Neural stem cells (NSCs) generate neurons of the cerebral cortex with distinct morphologies and functions. How specific neuron production, differentiation and migration are orchestrated is unclear. Hippo signaling regulates gene expression through Tead transcription factors (TFs). We show that Hippo transcriptional coactivators Yap1/Taz and the Teads have distinct functions during cortical development. Yap1/Taz promote NSC maintenance and Satb2 + neuron production at the expense of Tbr1 + neuron generation. However, Teads have moderate effects on NSC maintenance and do not affect Satb2 + neuron differentiation. Conversely, whereas Tead2 blocks Tbr1 + neuron formation, Tead1 and Tead3 promote this early fate. In addition, we found that Hippo effectors regulate neuronal migration to the cortical plate (CP) in a reciprocal fashion, that ApoE, Dab2 and Cyr61 are Tead targets, and these contribute to neuronal fate determination and migration. Our results indicate that multifaceted Hippo signaling is pivotal in different aspects of cortical development. NSCs of the developing cerebral cortex form the ventricular zone (VZ) lining the lumen of the neural tube 1-5. NSCs in the dorsal anterior forebrain are the major source of the projection neurons of the cerebral cortex 4,5. The mechanisms controlling the patterning and cell fate specification of these stem cells during early brain development are not clearly understood. Although various signaling pathways including Notch, Wnt, Shh, FGFs, TGF-β, Retinoic acid, Reelin and Hippo are known to regulate NSC proliferation and to control fate decisions, neurogenesis, and gliogenesis; the crosstalk between the different signaling pathways and the integration of these signals on target genes governing complex cell fate choices is unclear 1-3. Hippo signaling is evolutionarily conserved and a regulator of organ size control and tissue homeostasis 6-9. The pathway is regulated by numerous stimuli including G-protein coupled receptor signaling, mechanical stress, cellular energy status, cell-cell contact and cell-extra-cellular matrix interactions 6-8. Hippo signaling employs a cascade of phosphorylation steps mediated by the kinases Mst1/2 and Lats1/2 8-10. Lats1/2 phosphorylate the transcriptional coregulators Yap1 and Taz to promote cytoplasmic retention and subsequent degradation 6-8. When Hippo signaling is inactive, Yap1/Taz translocate to the nucleus and form multiple complexes with different DNA binding partners including TEADs, SMADs, and Runx TFs (Fig. S1a) 8-10. The Teads are major regulators of Hippo target genes in many systems including cancer 8,11,12. Fat4 and Dchs are receptor and ligand, respectively, of the Hippo pathway in embryonic NSCs. Knockdown of Fat4 results in increased proliferation in the developing nervous system and reduction of neuronal differentiation 13,14. Mutations in FAT4 and DCHS cause Van Maldergem syndrome in humans, an autosomal-recessive disorder characterized by in...

BackgroundThe mesencephalic dopaminergic (mDA) cell system is composed of two major groups of projecting cells in the Substantia Nigra (SN) (A9 neurons) and the Ventral Tegmental Area (VTA) (A10 cells). Selective degeneration of A9 neurons occurs in Parkinson’s disease (PD) while abnormal function of A10 cells has been linked to schizophrenia, attention deficit and addiction. The molecular basis that underlies selective vulnerability of A9 and A10 neurons is presently unknown.ResultsBy taking advantage of transgenic labeling, laser capture microdissection coupled to nano Cap-Analysis of Gene Expression (nanoCAGE) technology on isolated A9 and A10 cells, we found that a subset of Olfactory Receptors (OR)s is expressed in mDA neurons. Gene expression analysis was integrated with the FANTOM5 Helicos CAGE sequencing datasets, showing the presence of these ORs in selected tissues and brain areas outside of the olfactory epithelium. OR expression in the mesencephalon was validated by RT-PCR and in situ hybridization. By screening 16 potential ligands on 5 mDA ORs recombinantly expressed in an heterologous in vitro system, we identified carvone enantiomers as agonists at Olfr287 and able to evoke an intracellular Ca2+ increase in solitary mDA neurons. ORs were found expressed in human SN and down-regulated in PD post mortem brains.ConclusionsOur study indicates that mDA neurons express ORs and respond to odor-like molecules providing new opportunities for pharmacological intervention in disease.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-729) contains supplementary material, which is available to authorized users.