Stages Of Neuronal Maturation Research Articles

Generation of a Dcx-CreERT2 knock-in mouse for genetic manipulation of newborn neurons.

A wide variety of CreERT2 driver lines are available for genetic manipulation of adult-born neurons in the mouse brain. These tools have been instrumental in studying fate potential, migration, circuit integration, and morphology of the stem cells supporting lifelong neurogenesis. Despite a wealth of tools, genetic manipulation of adult-born neurons for circuit and behavioral studies has been limited by poor specificity of many driver lines targeting early progenitor cells and by the inaccessibility of lines selective for later stages of neuronal maturation. We sought to address these limitations by creating a new CreERT2 driver line targeted to the endogenous mouse doublecortin locus as a marker of fate-specified neuroblasts and immature neurons. Our new model places a T2A-CreERT2 cassette immediately downstream of the Dcx coding sequence on the X chromosome, allowing expression of both Dcx and CreERT2 proteins in the endogenous spatiotemporal pattern for this gene. We demonstrate that the new mouse line drives expression of a Cre-dependent reporter throughout the brain in neonatal mice and in known neurogenic niches of adult animals. The line has been deposited with the Jackson Laboratory and should provide an accessible tool for studies targeting fate-restricted neuronal precursors.

Asynchronous transcription and translation of neurotransmitter-related genes characterize the initial stages of neuronal maturation in Drosophila.

Neuron specification and maturation are essential for proper central nervous system development. However, the precise mechanisms that govern neuronal maturation, essential to shape and maintain neuronal circuitry, remain poorly understood. Here, we analyse early-born secondary neurons in the Drosophila larval brain, revealing that the early maturation of secondary neurons goes through 3 consecutive phases: (1) Immediately after birth, neurons express pan-neuronal markers but do not transcribe terminal differentiation genes; (2) Transcription of terminal differentiation genes, such as neurotransmitter-related genes VGlut, ChAT, or Gad1, starts shortly after neuron birth, but these transcripts are, however, not translated; (3) Translation of neurotransmitter-related genes only begins several hours later in mid-pupa stages in a coordinated manner with animal developmental stage, albeit in an ecdysone-independent manner. These results support a model where temporal regulation of transcription and translation of neurotransmitter-related genes is an important mechanism to coordinate neuron maturation with brain development.

Regional Patterning of Adult Neurogenesis in the Homing Pigeon's Brain.

In the avian brain, adult neurogenesis has been reported in the telencephalon of several species, but the functional significance of this trait is still ambiguous. Homing pigeons (Columba livia f.d.) are well-known for their navigational skills. Their brains are functionally adapted to homing with, e.g., larger hippocampi. So far, no comprehensive mapping of adult neuro- and gliogenesis or studies of different developmental neuronal stages in the telencephalon of homing pigeons exists, although comprehensive analyses in various species surely will result in a higher understanding of the functional significance of adult neurogenesis. Here, adult, free flying homing pigeons were treated with 5-bromo-deoxyuridine (BrdU) to label adult newborn cells. Brains were dissected and immunohistochemically processed with several markers (GFAP, Sox2, S100ß, Tbr2, DCX, Prox1, Ki67, NeuN, Calbindin, Calretinin) to study different stages of adult neurogenesis in a quantitative and qualitative way. Therefore, immature and adult newborn neurons and glial cells were analyzed along the anterior–posterior axis. The analysis proved the existence of different neuronal maturation stages and showed that immature cells, migrating neurons and adult newborn neurons and glia were widely and regionally unequally distributed. Double- and triple-labelling with developmental markers allowed a stage classification of adult neurogenesis in the pigeon brain (1: continuity of stem cells/proliferation, 2: fate specification, 3: differentiation/maturation, 4: integration). The most adult newborn neurons and glia were found in the intercalated hyperpallium (HI) and the hippocampal formation (HF). The highest numbers of immature (DCX+) cells were detected in the nidopallium (N). Generally, the number of newborn glial cells exceeded the number of newborn neurons. Individual structures (e.g., HI, N, and HF) showed further variations along the anterior–posterior axis. Our qualitative classification and the distribution of maturing cells in the forebrain support the idea that there is a functional specialization, respectively, that there is a link between brain-structure and function, species-specific requirements and adult neurogenesis. The high number of immature neurons also suggests a high level of plasticity, which points to the ability for rapid adaption to environmental changes through additive mechanisms. Furthermore, we discuss a possible influence of adult neurogenesis on spatial cognition.

Neuronal Activity Differentially Regulates KCC2 Protein Expression at Distinct Neuronal Maturation Stages

The K+/Cl‐ co‐transporter 2 (KCC2), a protein exclusively expressed in neurons, facilitates the co‐transport of a K+ and a Cl‐ ion across the cell membrane. The developmental shift of GABAA receptor mediated responses from depolarizing to hyperpolarizing is mainly due to a developmental upregulation of KCC2. Moreover, in mature neurons, neuronal activity leads to a decrease in surface expression and phosphorylation of Ser940 residue of KCC2, thereby reducing its activity. KCC2 is additionally phosphorylated at Thr906 and Thr1007, which reduces KCC2 surface expression and thus activity.Given the important role of neuronal activity in regulating KCC2 expression, we sought to investigate the effect of pilocarpine or 4‐aminopyridine (4AP) treatment on KCC2 expression across different maturation stages of neurons using quantitative RT‐PCR, immunocytochemistry (ICC) and immunoblotting. We also investigated the three phosphorylation sites – Ser940, Thr906 and Thr1007 – of KCC2. Immature neurons (day in vitro 4) from embryonic day 18.5 mouse hippocampus were treated with pilocarpine or 4AP (100µM, 60 minutes). The results show that 4AP or pilocarpine treatment has no effect on KCC2 transcript or protein expression, compared to controls. Similarly, ICC and immunoblotting results showed that there was no change in the phosphorylation status of Ser940. ICC results also showed that the phosphorylation status of Thr906 and Thr1007 remained unaltered in immature neurons after pilocarpine treatment.In day in vitro 17 organotypic hippocampal slices cultured from postnatal day 2 mouse pups, immunoblotting showed that treatment with 4AP did not affect KCC2 protein expression. However, in day in vitro 35 organotypic hippocampal slice cultures, 4AP treatment reduced KCC2 whole protein expression.These results demonstrate that neuronal activity has a distinctive effect on KCC2 protein as the neurons mature, suggesting a differential regulation of KCC2 protein at different maturation stages.

In vitro monitoring of HTR2A-positive neurons derived from human-induced pluripotent stem cells

The serotonin 5-HT2A receptor (5-HT2AR) has been receiving increasing attention because its genetic variants have been associated with a variety of neurological diseases. To elucidate the pathogenesis of the neurological diseases associated with 5-HT2AR gene (HTR2A) variants, we have previously established a protocol to induce HTR2A-expressing neurons from human-induced pluripotent stem cells (hiPSCs). Here, we investigated the maturation stages and electrophysiological properties of HTR2A-positive neurons induced from hiPSCs and constructed an HTR2A promoter-specific reporter lentivirus to label the neurons. We found that neuronal maturity increased over time and that HTR2A expression was induced at the late stage of neuronal maturation. Furthermore, we demonstrated successful labelling of the HTR2A-positive neurons, which had fluorescence and generated repetitive action potentials in response to depolarizing currents and an inward current during the application of TCB-2, a selective agonist of 5-HT2ARs, respectively. These results indicated that our in vitro model mimicked the in vivo dynamics of 5-HT2AR. Therefore, in vitro monitoring of the function of HTR2A-positive neurons induced from hiPSCs could help elucidate the pathophysiological mechanisms of neurological diseases associated with genetic variations of the HTR2A gene.

Differential Influence of Sample Sex and Neuronal Maturation on mRNA and Protein Transport in Induced Human Neurons.

Nucleocytoplasmic transport (NCT) across thenuclear envelope (NE) is tightly regulated in eukaryotic cells and iscritical for maintaining cellular homeostasis. Its dysregulationleads to aging and neurodegeneration. Because they maintainaging-associated hallmarks, directly reprogrammed neurons from human fibroblasts are invaluable in understanding NCT. However, it is not clear whether NCT activity is influenced by neuronal maturation and sample sex [a key biological variable emphasized by the National Institutes of Health (NIH) policy]. We examined here NCT activity at the single-cell level by measuring mRNA subcellular distribution and protein transport in directly induced motor neurons (diMNs) from adult human fibroblasts. The results show that mRNA subcellular distribution but not protein transport is affected by neuronal maturation stages, whereas both transport processes are not influenced by the sample sex. This study also provides quantitative methods and optimized conditions for measuring NCTs of mRNAs or protein cargoes, establishing a robust way for future functional examinations of NCT activity in directly induced neurons from diseased human patients.

The pharmacological reduction of hippocampal neurogenesis attenuates the protective effects of cannabidiol on cocaine voluntary intake.

The administration of cannabidiol has shown promising evidence in the treatment of some neuropsychiatric disorders, including cocaine addiction. However, little information is available as to the mechanisms by which cannabidiol reduces drug use and compulsive seeking. We investigated the role of adult hippocampal neurogenesis in reducing cocaine voluntary intake produced by repeated cannabidiol treatment in mice. Cocaine intake was modelled using the intravenous cocaine self-administration procedure in CD1 male mice. Cannabidiol (20mg/kg) reduced cocaine self-administration behaviour acquisition and total cocaine intake and enhanced adult hippocampal neurogenesis. Our results show that a 6-day repeated temozolomide treatment (25mg/kg/day), a chemotherapy drug that blocks hippocampal neurogenesis, prevented cannabidiol-induced increment in the early stages of neuronal maturation and differentiation, without altering the basal levels of BrdU/NeuN and doublecortin immunostaining. The reduction of total cocaine intake and operant behaviour acquisition observed following cannabidiol exposure was attenuated by temozolomide treatment. Our results also show a similar effect of temozolamide on a cannabidiol-induced improvement of novel object recognition memory, a task influenced by the proneurogenic effects of cannabidiol (10 and 20mg/kg). The anxiolytic effects of cannabidiol (10 and 20mg/kg), however, remained unaffected after its proneurogenic effects decreased. The present study confirms that adult hippocampal neurogenesis is one of the mechanisms by which cannabidiol lowers cocaine reinforcement and demonstrates the functional implication of adult hippocampal neurogenesis in cocaine voluntary consumption in mice. Such findings highlight the possible use of cannabidiol for developing new pharmacotherapies to manage cocaine use disorders.

JNK Isoforms Are Involved in the Control of Adult Hippocampal Neurogenesis in Mice, Both in Physiological Conditions and in an Experimental Model of Temporal Lobe Epilepsy.

Neurogenesis in the adult dentate gyrus (DG) of the hippocampus allows the continuous generation of new neurons. This cellular process can be disturbed under specific environmental conditions, such as epileptic seizures; however, the underlying mechanisms responsible for their control remain largely unknown. Although different studies have linked the JNK (c-Jun-N-terminal-kinase) activity with the regulation of cell proliferation and differentiation, the specific function of JNK in controlling adult hippocampal neurogenesis is not well known. The purpose of this study was to analyze the role of JNK isoforms (JNK1/JNK2/JNK3) in adult-hippocampal neurogenesis. To achieve this goal, we used JNK-knockout mice (Jnk1-/-, Jnk2-/-, and Jnk3-/-), untreated and treated with intraperitoneal injections of kainic acid (KA), as an experimental model of epilepsy. In each condition, we identified cell subpopulations at different stages of neuronal maturation by immunohistochemical specific markers. In physiological conditions, we evidenced that JNK1 and JNK3 control the levels of one subtype of early progenitor cells (GFAP+/Sox2+) but not the GFAP+/Nestin+ cell subtype. Moreover, the absence of JNK1 induces an increase of immature neurons (Doublecortin+; PSA-NCAM+ cells) compared with wild-type (WT). On the other hand, Jnk1-/- and Jnk3-/- mice showed an increased capacity to maintain hippocampal homeostasis, since calbindin immunoreactivity is higher than in WT. An important fact is that, after KA injection, Jnk1-/- and Jnk3-/- mice show no increase in the different neurogenic cell subpopulation analyzed, in contrast to what occurs in WT and Jnk2-/- mice. All these data support that JNK isoforms are involved in the adult neurogenesis control.

Precise temporal regulation of alternative splicing during neural development

Alternative splicing (AS) is one crucial step of gene expression that must be tightly regulated during neurodevelopment. However, the precise timing of developmental splicing switches and the underlying regulatory mechanisms are poorly understood. Here we systematically analyze the temporal regulation of AS in a large number of transcriptome profiles of developing mouse cortices, in vivo purified neuronal subtypes, and neurons differentiated in vitro. Our analysis reveals early-switch and late-switch exons in genes with distinct functions, and these switches accurately define neuronal maturation stages. Integrative modeling suggests that these switches are under direct and combinatorial regulation by distinct sets of neuronal RNA-binding proteins including Nova, Rbfox, Mbnl, and Ptbp. Surprisingly, various neuronal subtypes in the sensory systems lack Nova and/or Rbfox expression. These neurons retain the “immature” splicing program in early-switch exons, affecting numerous synaptic genes. These results provide new insights into the organization and regulation of the neurodevelopmental transcriptome.

Actin Waves Do Not Boost Neurite Outgrowth in the Early Stages of Neuron Maturation.

During neurite development, Actin Waves (AWs) emerge at the neurite base and move up to its tip, causing a transient retraction of the Growth Cone (GC). Many studies have shown that AWs are linked to outbursts of neurite growth and, therefore, contribute to the fast elongation of the nascent axon. Using long term live cell-imaging, we show that AWs do not boost neurite outgrowth and that neurites without AWs can elongate for several hundred microns. Inhibition of Myosin II abolishes the transient GC retraction and strongly modifies the AWs morphology. Super-resolution nanoscopy shows that Myosin IIB shapes the growth cone-like AWs structure and is differently distributed in AWs and GCs. Interestingly, depletion of membrane cholesterol and inhibition of Rho GTPases decrease AWs frequency and velocity. Our results indicate that Myosin IIB, membrane tension, and small Rho GTPases are important players in the regulation of the AW dynamics. Finally, we suggest a role for AWs in maintaining the GCs active during environmental exploration.

Noonan syndrome-associated SHP2 mutation differentially modulates the expression of postsynaptic receptors according to developmental maturation

Glutamate is the major excitatory neurotransmitter in the central nervous system, and related signaling involves both AMPA and NMDA subtype receptors. The expression of glutamate receptors is dynamically regulated during development. Recent studies showed that the dysregulation of glutamate receptor expression and function is associated with neurodevelopmental disorders including intellectual disability. Previously, a Noonan syndrome (NS)-associated SHP2 mutation (SHP2D61G) was shown to increase the synaptic delivery of AMPA receptor, subsequently impairing synaptic plasticity and learning in adult mice. However, how the mutant SHP2 affects glutamate receptor expression during development is not known. Here, we found that the SHP2D61G differentially regulates the expression of AMPA and NMDA receptors depending on the stage of neuronal maturation. In cultured neurons (immature stage; DIV 6), overexpression of SHP2D61G significantly increased the average size and the number of NMDA receptor-containing particles, but not those with AMPA receptors. In early matured neurons (DIV 12), SHP2D61G significantly increased only the average size of AMPA receptor particles, and subsequently increased their number in matured neurons (DIV 18). Importantly, all the changes described above for SHP2D61G neurons were reversed by inhibiting MAPK. These data demonstrate that the increased activation of MAPK signaling pathway by SHP2D61G could deregulate the surface expression of synaptic receptors during neuronal development, which likely contributes to cognitive impairments in NS patients.

Thinking with your stomach? Gut feelings on microbiome modulation of brain structure and function (Commentary on Luczynski etal.).

Is that a rumbling I feel in my stomach? Or perhaps it is the trillions of bacteria down there who are in revolt, fomenting (or fermenting!) a microbial revolution? No active biologist or medical researcher can easily ignore the revolution in gut microbiome research in recent years. It seems that the gut microbiome, the entire microbial ecosystem occupying the gastrointestinal ecological niche, can impact almost every organ in the human body, not least of which being the brain. The gut microbiome has been found to signal to both the developing and adult mammalian brain, modulating both health and disease states (Cryan and Dinan, 2012; Mayer et al., 2014). This article is protected by copyright. All rights reserved.

Task Learning Promotes Plasticity of Interneuron Connectivity Maps in the Olfactory Bulb.

Elucidating patterns of functional synaptic connectivity and deciphering mechanisms of how plasticity influences such connectivity is essential toward understanding brain function. In the mouse olfactory bulb (OB), principal neurons (mitral/tufted cells) make reciprocal connections with local inhibitory interneurons, including granule cells (GCs) and external plexiform layer (EPL) interneurons. Our current understanding of the functional connectivity between these cell types, as well as their experience-dependent plasticity, remains incomplete. By combining acousto-optic deflector-based scanning microscopy and genetically targeted expression of Channelrhodopsin-2, we mapped connections in a cell-type-specific manner between mitral cells (MCs) and GCs or between MCs and EPL interneurons. We found that EPL interneurons form broad patterns of connectivity with MCs, whereas GCs make more restricted connections with MCs. Using an olfactory associative learning paradigm, we found that these circuits displayed differential features of experience-dependent plasticity. Whereas reciprocal connectivity between MCs and EPL interneurons was nonplastic, the connections between GCs and MCs were dynamic and adaptive. Interestingly, experience-dependent plasticity of GCs occurred only in certain stages of neuronal maturation. We show that different interneuron subtypes form distinct connectivity maps and modes of experience-dependent plasticity in the OB, which may reflect their unique functional roles in information processing. Deducing how specific interneuron subtypes contribute to normal circuit function requires understanding the dynamics of their connections. In the olfactory bulb (OB), diverse interneuron subtypes vastly outnumber principal excitatory cells. By combining acousto-optic deflector-based scanning microscopy, electrophysiology, and genetically targeted expression of Channelrhodopsin-2, we mapped the functional connectivity between mitral cells (MCs) and OB interneurons in a cell-type-specific manner. We found that, whereas external plexiform layer (EPL) interneurons show broadly distributed patterns of stable connectivity with MCs, adult-born granule cells show dynamic and plastic patterns of synaptic connectivity with task learning. Together, these findings reveal the diverse roles for interneuons within sensory circuits toward information learning and processing.

The Temporal Expression Pattern of Alpha-Synuclein Modulates Olfactory Neurogenesis in Transgenic Mice

BackgroundAdult neurogenesis mirrors the brain´s endogenous capacity to generate new neurons throughout life. In the subventricular zone/ olfactory bulb system adult neurogenesis is linked to physiological olfactory function and has been shown to be impaired in murine models of neuronal alpha-Synuclein overexpression. We analyzed the degree and temporo-spatial dynamics of adult olfactory bulb neurogenesis in transgenic mice expressing human wild-type alpha-Synuclein (WTS) under the murine Thy1 (mThy1) promoter, a model known to have a particularly high tg expression associated with impaired olfaction.ResultsSurvival of newly generated neurons (NeuN-positive) in the olfactory bulb was unchanged in mThy1 transgenic animals. Due to decreased dopaminergic differentiation a reduction in new dopaminergic neurons within the olfactory bulb glomerular layer was present. This is in contrast to our previously published data on transgenic animals that express WTS under the control of the human platelet-derived growth factor β (PDGF) promoter, that display a widespread decrease in survival of newly generated neurons in regions of adult neurogenesis, resulting in a much more pronounced neurogenesis deficit. Temporal and quantitative expression analysis using immunofluorescence co-localization analysis and Western blots revealed that in comparison to PDGF transgenic animals, in mThy1 transgenic animals WTS is expressed from later stages of neuronal maturation only but at significantly higher levels both in the olfactory bulb and cortex.ConclusionsThe dissociation between higher absolute expression levels of alpha-Synuclein but less severe impact on adult olfactory neurogenesis in mThy1 transgenic mice highlights the importance of temporal expression characteristics of alpha-Synuclein on the maturation of newborn neurons.

Time course of spinal doublecortin expression in developing rat and porcine spinal cord: implication in in vivo neural precursor grafting studies.

Expression of doublecortin (DCX), a 43-53 kDa microtubule binding protein, is frequently used as (i) an early neuronal marker to identify the stage of neuronal maturation of in vivo grafted neuronal precursors (NSCs), and (ii) a neuronal fate marker transiently expressed by immature neurons during development. Reliable identification of the origin of DCX-immunoreactive cells (i.e., host vs. graft) requires detailed spatial and temporal mapping of endogenous DCX expression at graft-targeted brain or spinal cord regions. Accordingly, in the present study, we analyzed (i) the time course of DCX expression in pre- and postnatal rat and porcine spinal cord, and (ii) the DCX expression in spinally grafted porcine-induced pluripotent stem cells (iPS)-derived NSCs and human embryonic stem cell (ES)-derived NSCs. In addition, complementary temporospatial GFAP expression study in porcine spinal cord was also performed. In 21-day-old rat fetuses, an intense DCX immunoreactivity distributed between the dorsal horn (DH) and ventral horn was seen and was still present in the DH neurons on postnatal day 20. In animals older than 8 weeks, no DCX immunoreactivity was seen at any spinal cord laminae. In contrast to rat, in porcine spinal cord (gestational period 113-114 days), DCX was only expressed during the pre-natal period (up to 100 days) but was no longer present in newborn piglets or in adult animals. Immunohistochemical analysis was confirmed with a comparable expression profile by western blot analysis. Contrary, the expression of porcine GFAP started within 70-80 days of the pre-natal period. Spinally grafted porcine iPS-NSCs and human ES-NSCs showed clear DCX expression at 3-4 weeks postgrafting. These data indicate that in spinal grafting studies which employ postnatal or adult porcine models, the expression of DCX can be used as a reliable marker of grafted neurons. In contrast, if grafted neurons are to be analyzed during the first 4 postnatal weeks in the rat spinal cord, additional markers or grafted cell-specific labeling techniques need to be employed to reliably identify grafted early postmitotic neurons and to differentiate the DCX expression from the neurons of the host.

Genetics studies indicate that neural induction and early neuronal maturation are disturbed in autism.

Postmortem neuropathological studies of autism consistently reveal distinctive types of malformations, including cortical dysplasias, heterotopias, and various neuronomorphometric abnormalities. In keeping with these observations, we review here that 88% of high-risk genes for autism influence neural induction and early maturation of the neuroblast. In addition, 80% of these same genes influence later stages of differentiation, including neurite and synapse development, suggesting that these gene products exhibit long-lasting developmental effects on cell development as well as elements of redundancy in processes of neural proliferation, growth, and maturation. We also address the putative genetic overlap of autism with conditions like epilepsy and schizophrenia, with implications to shared and divergent etiologies. This review imports the necessity of a frameshift in our understanding of the neurodevelopmental basis of autism to include all stages of neuronal maturation, ranging from neural induction to synaptogenesis.

The Philosopher’s Stone of Reprogramming

A hierarchical transcriptional mechanism governs direct conversion of mouse embryonic fibroblasts to neurons.

Functional recovery of the dentate gyrus after a focal lesion is accompanied by structural reorganization in the adult rat

The adult brain is highly plastic and tends to undergo substantial reorganization after injury to compensate for the lesion effects. It has been shown that such reorganization mainly relies on anatomical and biochemical modifications of the remaining cells which give rise to a network rewiring without reinstating the original morphology of the damaged region. However, few studies have analyzed the neurorepair potential of a neurogenic structure. Thus, the aim of this work was to analyze if the DG could restore its original morphology after a lesion and to establish if the structural reorganization is accompanied by behavioral and electrophysiological recovery. Using a subepileptogenic injection of kainic acid (KA), we induced a focal lesion in the DG and assessed in time (1) the loss and recovery of dependent and non dependent DG cognitive functions, (2) the anatomical reorganization of the DG using a stereological probe and immunohistochemical markers for different neuronal maturation stages and, (3) synaptic plasticity as assessed through the induction of in vivo long-term potentiation (LTP) in the mossy fiber pathway (CA3-DG). Our results show that a DG focal lesion with KA leads to a well delimited region of neuronal loss, disorganization of the structure, the loss of associated mnemonic functions and the impairment to elicit LTP. However, behavioral and synaptic plasticity expression occurs in a time dependent fashion and occurs along the morphological restoration of the DG. These results provide novel information on neural plasticity events associated to functional reorganization after damage.

A non-invasive method to isolate the neuronal linage from the nasal epithelium from schizophrenic and bipolar diseases

Brain imaging and histopathological studies suggest that neurodevelopmental anomalies play a key role in the etiology of schizophrenia (SZ) and bipolar disorder (BD). New neuron formation and maturation occur in human olfactory epithelium throughout life. Therefore, the olfactory epithelium has been proposed as a model to study alterations in neurodevelopment, particularly in some psychiatric diseases. However, former studies were done with olfactory epithelium biopsies taken post mortem or under anesthesia from patients with SZ and BD. In this work we have developed a new method to obtain viable neural precursors by exfoliation of the anterior region of the medial lateral turbinate of the nasal cavity from healthy controls, and ambulatory patients. Cells were propagated to establish neural precursor banks. Thawed cells showed cytoskeletal phenotypes typical of developing neurons. They also conserved the ability to differentiate in presence of 2mM dibutyril-cyclic adenosine monophosphate, and maintained voltage-operated Ca2+ currents in culture. Moreover, proportions of neuronal maturation stages were maintained in cultured exfoliates obtained from SZ and BD patients. Data support that neural precursors obtained from a nasal exfoliate are an excellent experimental model to later approach studies on biomarkers, neural development and cellular alterations in the pathophysiology of SZ and BD.

Fluid accumulation in the fetal extracerebral spaces: External hydrocephalus or subdural hygromas?

External hydrocephalus is defined as enlargement of the subarachnoidal space with accumulation of cerebrospinal fluid (CSF). In adults, there are several reasons for external hydrocephalus, such as disruption of CSF resorption or meningeal inflammations. During fetal development the occurrence of external hydrocephalus is a very rare event and pathogenetic mechanism as well as neuropathological classification considerably differs from that of adults. Here we report on a 25th gestational week fetus with the ultrasonic diagnosis of an external hydrocephalus with macrocephalus and microencephaly. Neuropathological examination revealed extensive subdural hygroma, associated with chronic subdural haemorrhages. The central nervous system (CNS) showed a distinct microencephaly with pronounced neocortical migration defects and various stages of neuronal maturation. Due to our findings we were able to exclude the diagnosis of an external hydrocephalus. Instead, we suggest, that the atrophic hemispheres lead to a chronic stretch of the bridging veins with drainage of fluid into the subdural space.