Molecular and cellular logic of cerebral cortex development, evolution, and disease

Editorial on the Research Topic Molecular and cellular logic of cerebral cortex development, evolution, and diseas

Human Neural Stem Cell Systems to Explore Pathogen-Related Neurodevelopmental and Neurodegenerative Disorders

Building and functioning of the human brain requires the precise orchestration and execution of myriad molecular and cellular processes, across a multitude of cell types and over an extended period of time. Dysregulation of these processes affects structure and function of the brain and can lead to neurodevelopmental, neurological, or psychiatric disorders. Multiple environmental stimuli affect neural stem cells (NSCs) at several levels, thus impairing the normal human neurodevelopmental program. In this review article, we will delineate the main mechanisms of infection adopted by several neurotropic pathogens, and the selective NSC vulnerability. In particular, TORCH agents, i.e., Toxoplasma gondii, others (including Zika virus and Coxsackie virus), Rubella virus, Cytomegalovirus, and Herpes simplex virus, will be considered for their devastating effects on NSC self-renewal with the consequent neural progenitor depletion, the cellular substrate of microcephaly. Moreover, new evidence suggests that some of these agents may also affect the NSC progeny, producing long-term effects in the neuronal lineage. This is evident in the paradigmatic example of the neurodegeneration occurring in Alzheimer's disease

Zika Virus Disrupts Phospho-TBK1 Localization and Mitosis in Human Neuroepithelial Stem Cells and Radial Glia

Graphical Abstract Highlights d Derivation of human neocortical and spinal cord neuroepithelial stem (NES) cells d Zika virus (ZIKV) infects NES cells and radial glia, impairing mitosis and survival d ZIKV induces mitochondrial sequestration of centrosomal phospho-TBK1 d Nucleoside analogs inhibit ZIKV replication, protecting NES cells from cell death In Brief Onorati et al. establish neuroepithelial stem (NES) cells as a model for studying human neurodevelopment and ZIKV-induced microcephaly. Together with analyses in human brain slices and microcephalic human fetal tissue, they find that ZIKV predominantly infects NES and radial glial cells, reveal a pivotal role for pTBK1, and find that nucleoside analogs inhibit ZIKV replication, protecting NES cells from cell death

GPCRs signaling in striatal neurons: modulation of AMPA phosphorylation by group I metabotropic glutamate receptors

The striatum is the main input structure of the basal ganglia circuit and receives a dense glutamatergic innervation from several areas of cortex and thalamus. Glutamate acts on striatal neurons through two main classes of receptors, namely ionotropic and metabotropic receptors. Ionotropic receptors include AMPA (3-hydroxy-5-methylisoxazole-4-propionic acid), NMDA (N-methyl-D-aspartic acid) and kainate receptors, whereas metabotropic glutamate receptors (mGluRs) include three groups of receptors classified on the basis of their pharmacology and signaling properties. Group I mGluRs are widely expressed in striatum and enclose two receptor subtypes, mGlu1 and mGlu5. Phosphorylation is an important mechanism for the post-translational modulation of ionotropic glutamate receptors, and in this study, I investigated the regulation of AMPA receptor GluR1 subunit phosphorylation by the stimulation of group I mGluRs in the mouse dorsal striatum. To this purpose, I used striatal slices as experimental model of investigation. Stimulation of group I mGluRs with DHPG (3,5-dihydroxyphenylglycine) was found to increase GluR1 phosphorylation at the cAMP-dependent protein kinase (PKA) site, Ser845, in a concentration-dependent manner. This effect was abolished by treating striatal slices with the selective mGlu5 antagonist MPEP (2-methyl-6-(phenylethynyl) pyridine hydrochloride) but not with the selective mGlu1 antagonist LY367385, thus suggesting a major contribution of mGlu5 receptors in the phosphorylation of GluR1 at Ser845. Blockade of dopamine D1 receptors with SCH23390 did not affect phosphorylation of Ser845 evoked by stimulation of group I mGluRs. Conversely, blockade of adenosine A2A receptors with ZM241385, or treatment with adenosine deaminase (ADA) which converts endogenous adenosine to inosine, abolished the effect of DHPG. These results suggest that mGlu5 receptors require endogenous adenosine, and consequently the activation of A2A receptors, to promote phosphorylation of GluR1 at Ser845. Direct stimulation of A2A receptors with the selective agonist CGS21680 did not produce any significant effect on phosphorylation of GluR1. However, co-treatment of striatal slices with DHPG restored the increase in phosphorylation of Ser845. These findings demonstrate that mGlu5 receptors enhance phosphorylation of GluR1 at Ser845 potentiating the effect of endogenous adenosine on A2A receptors. Since adenosine A2A receptors in striatum are selectively expressed in striatopallidal neurons, the results presented here also indicate that the effect exerted by mGlu5 receptors occurs selectively in this neuronal subpopulation. The increase in Ser845 phosphorylation was also found to be dependent on DARPP-32 (Dopamine and cAMP-regulated phosphoprotein of 32 kDa), a protein highly enriched in striatal neurons. Indeed, the effect produced by DHPG was abolished in mutant mice in which the PKA phosphorylation site on DARPP-32 was mutated into an alanin residue. When phosphorylated by PKA, DARPP-32 inhibits protein phosphatase-1 (PP-1), which dephosphorylates GluR1 at Ser845. Therefore, these results suggest that DARPP-32-mediated inhibition of PP-1 is necessary to preserve the effect of DHPG on AMPA receptors. Collectively, these data demonstrate that stimulation of mGlu5 receptors enhances the phosphorylation of GluR1 subunit at Ser845 in striatopallidal neurons, through two pathways: a direct pathway, in which mGlu5 receptors activate PKA recruiting the A2A receptors signal transduction machinery thus potentiating the effect of endogenous adenosine, and an indirect pathway, in which the increment in phosphorylation is obtained through an inhibition of dephosphorylation mediated by DARPP-32. These findings clarify the molecular mechanisms underlying the glutamatergic neurotransmission in striatum, which is involved in the striatal synaptic plasticity and consequently in behavioral and cognitive functions of this nucleus

Setting a highway for converting skin into neurons

Direct conversion of human skin fibroblasts into induced neuronal (iN) cells has been recently achieved by using different combinations of transcription factors eventually associated with microRNAs. These findings lay the ground for a straightforward and efficient generation of human neurons in vitro with elaborated functional properties instrumental for disease modeling and cell-based approaches of brain repair

Microcephaly-associated protein WDR62 shuttles from the Golgi apparatus to the spindle poles in human neural progenitors

WDR62 is a spindle pole-associated scaffold protein with pleiotropic functions. Recessive mutations in WDR62 cause structural brain abnormalities and account for the second most common cause of autosomal recessive primary microcephaly (MCPH), indicating WDR62 as a critical hub for human brain development. Here, we investigated WDR62 function in corticogenesis through the analysis of a C-terminal truncating mutation (D955AfsX112). Using induced Pluripotent Stem Cells (iPSCs) obtained from a patient and his unaffected parent, as well as isogenic corrected lines, we generated 2D and 3D models of human neurodevelopment, including neuroepithelial stem cells, cerebro-cortical progenitors, terminally differentiated neurons, and cerebral organoids. We report that WDR62 localizes to the Golgi apparatus during interphase in cultured cells and human fetal brain tissue, and translocates to the mitotic spindle poles in a microtubule-dependent manner. Moreover, we demonstrate that WDR62 dysfunction impairs mitotic progression and results in alterations of the neurogenic trajectories of iPSC neuroderivatives. In summary, impairment of WDR62 localization and function results in severe neurodevelopmental abnormalities, thus delineating new mechanisms in the etiology of MCPH

Rapid generation of functional dopaminergic neurons from human induced pluripotent stem cells through a single-step procedure using cell lineage transcription factors

Current protocols for in vitro differentiation of human induced pluripotent stem cells (hiPSCs) to generate dopamine (DA) neurons are laborious and time-expensive. In order to accelerate the overall process, we have established a fast protocol by expressing the developmental transcription factors ASCL1, NURR1, and LMX1A. With this method, we were able to generate mature and functional dopaminergic neurons in as few as 21 days, skipping all the intermediate steps for inducting and selecting embryoid bodies and rosette-neural precursors. Strikingly, the resulting neuronal conversion process was very proficient, with an overall efficiency that was more than 93% of all the coinfected cells. hiPSC-derived DA neurons expressed all the critical molecular markers of the DA molecular machinery and exhibited sophisticated functional features including spontaneous electrical activity and dopamine release. This one-step protocol holds important implications for in vitro disease modeling and is particularly amenable for exploitation in high-throughput screening protocols

Remote control of induced dopaminergic neurons in parkinsonian rats

Direct lineage reprogramming through genetic-based strategies enables the conversion of differentiated somatic cells into functional neurons and distinct neuronal subtypes. Induced dopaminergic (iDA) neurons can be generated by direct conversion of skin fibroblasts; however, their in vivo phenotypic and functional properties remain incompletely understood, leaving their impact on Parkinson's disease (PD) cell therapy and modeling uncertain. Here, we determined that iDA neurons retain a transgene-independent stable phenotype in culture and in animal models. Furthermore, transplanted iDA neurons functionally integrated into host neuronal tissue, exhibiting electrically excitable membranes, synaptic currents, dopamine release, and substantial reduction of motor symptoms in a PD animal model. Neuronal cell replacement approaches will benefit from a system that allows the activity of transplanted neurons to be controlled remotely and enables modulation depending on the physiological needs of the recipient; therefore, we adapted a DREADD (designer receptor exclusively activated by designer drug) technology for remote and real-time control of grafted iDA neuronal activity in living animals. Remote DREADD-dependent iDA neuron activation markedly enhanced the beneficial effects in transplanted PD animals. These data suggest that iDA neurons have therapeutic potential as a cell replacement approach for PD and highlight the applicability of pharmacogenetics for enhancing cellular signaling in reprogrammed cell-based approaches