Role In Cortical Development Research Articles

Basal forebrain cholinergic neurons have specific characteristics during the perinatal period.

Cholinergic neurons of the basal forebrain (BF) represent the main source of cholinergic innervation of large parts of the neocortex and are involved in adults in the modulation of attention, memory, and arousal. During the first postnatal days, they play a crucial role in the development of cortical neurons and cortical cytoarchitecture. However, their characteristics, during this period have not been studied. To understand how they can fulfill this role, we investigated the morphological and electrophysiological maturation of cholinergic neurons of the substantia innominata-nucleus basalis of Meynert complex (SI/NBM) in the perinatal period in mice. We show that cholinergic neurons, whether or not they express γ-aminobutyric acid (GABA) as a co-transmitter, are already functional at embryonic day 18 (E18). Until the end of the first postnatal week, they constitute a single population of neurons with a well-developed dendritic tree, a spontaneous activity including bursting periods, and a short latency response to depolarizations (early-firing). They are excited by both their GABAergic and glutamatergic afferents. During the second postnatal week, a second, less excitable, neuronal population emerges, with a longer delay response to depolarizations (late-firing), together with the hyperpolarizing action of GABAAR-mediated currents. This classification into early-firing (40%) and late-firing (60%) neurons, is again independent of the co-expression of GABAergic markers. These results strongly suggest that during the first postnatal week, the specific properties of developing SI/NBM cholinergic neurons allow them to spontaneously release acetylcholine, or acetylcholine and GABA, into the developing cortex.Significance statement During early postnatal days, basal forebrain cholinergic neurons from the substantia innominata-nucleus basalis of Meynert complex (SI/NBM) play a crucial role in cortical development. However, their morphological and electrophysiological characteristics have not been studied during this period. Here we show that perinatal SI/NBM cholinergic, whether they still/have co-expressed GABAergic markers, belong to a single, homogeneous population of spontaneously active, early-firing, bursting neurons, activated by both glutamatergic and GABAergic afferents until the GABAARs-mediated current polarity shift from excitatory to inhibitory has occurred. This early high excitability suggests that they can release acetylcholine or acetylcholine and GABA into the developing cortical layers and fulfill their well-described role on the early development of cortical neurons and networks.

GTF2I dosage regulates neuronal differentiation and social behavior in 7q11.23 neurodevelopmental disorders.

Copy number variations at 7q11.23 cause neurodevelopmental disorders with shared and opposite manifestations. Deletion causes Williams-Beuren syndrome featuring hypersociability, while duplication causes 7q11.23 microduplication syndrome (7Dup), frequently exhibiting autism spectrum disorder (ASD). Converging evidence indicates GTF2I as key mediator of the cognitive-behavioral phenotypes, yet its role in cortical development and behavioral hallmarks remains largely unknown. We integrated proteomic and transcriptomic profiling of patient-derived cortical organoids, including longitudinally at single-cell resolution, to dissect 7q11.23 dosage-dependent and GTF2I-specific disease mechanisms. We observed dosage-dependent impaired dynamics of neural progenitor proliferation, transcriptional imbalances, and highly specific alterations in neuronal output, leading to precocious excitatory neuron production in 7Dup, which was rescued by restoring physiological GTF2I levels. Transgenic mice with Gtf2i duplication recapitulated progenitor proliferation and neuronal differentiation defects alongside ASD-like behaviors. Consistently, inhibition of lysine demethylase 1 (LSD1), a GTF2I effector, was sufficient to rescue ASD-like phenotypes in transgenic mice, establishing GTF2I-LSD1 axis as a molecular pathway amenable to therapeutic intervention in ASD.

Activation of the PI3K/AKT/mTOR Pathway in Cajal–Retzius Cells Leads to Their Survival and Increases Susceptibility to Kainate-Induced Seizures

Cajal-Retzius cells (CRs) are a class of transient neurons in the mammalian cortex that play a critical role in cortical development. Neocortical CRs undergo almost complete elimination in the first two postnatal weeks in rodents and the persistence of CRs during postnatal life has been detected in pathological conditions related to epilepsy. However, it is unclear whether their persistence is a cause or consequence of these diseases. To decipher the molecular mechanisms involved in CR death, we investigated the contribution of the PI3K/AKT/mTOR pathway as it plays a critical role in cell survival. We first showed that this pathway is less active in CRs after birth before massive cell death. We also explored the spatio-temporal activation of both AKT and mTOR pathways and reveal area-specific differences along both the rostro-caudal and medio-lateral axes. Next, using genetic approaches to maintain an active pathway in CRs, we found that the removal of either PTEN or TSC1, two negative regulators of the pathway, lead to differential CR survivals, with a stronger effect in the Pten model. Persistent cells in this latter mutant are still active. They express more Reelin and their persistence is associated with an increase in the duration of kainate-induced seizures in females. Altogether, we show that the decrease in PI3K/AKT/mTOR activity in CRs primes these cells to death by possibly repressing a survival pathway, with the mTORC1 branch contributing less to the phenotype.

A Human-Specific De Novo Gene Promotes Cortical Expansion and Folding.

Newly originated de novo genes have been linked to the formation and function of the human brain. However, how a specific gene originates from ancestral noncoding DNAs and becomes involved in the preexisting network for functional outcomes remains elusive. Here, a human-specific de novo gene, SP0535, is identified that is preferentially expressed in the ventricular zone of the human fetal brain and plays an important role in cortical development and function. In human embryonic stem cell-derived cortical organoids, knockout of SP0535compromises their growth and neurogenesis. In SP0535transgenic (TG) mice, expression of SP0535induces fetal cortex expansion and sulci and gyri-like structure formation. The progenitors and neurons in the SP0535TG mouse cortex tend to proliferate and differentiate in ways that are unique to humans. SP0535TG adult mice also exhibit improved cognitive ability and working memory. Mechanistically, SP0535interacts with the membrane protein Na+ /K+ ATPase subunit alpha-1 (ATP1A1) and releases Src from the ATP1A1-Src complex, allowing increased level of Src phosphorylation that promotes cell proliferation. Thus, SP0535is the first proven human-specific de novo gene that promotes cortical expansion and folding, and can function through incorporating into an existing conserved molecular network.

Longitudinal Effects of Asymptomatic C9orf72 Carriership on Brain Morphology.

We investigated effects of C9orf72 repeat expansion and gene expression on longitudinal cerebral changes before symptom onset. We enrolled 79 asymptomatic family members (AFMs) from 9 families with C9orf72 repeat expansion. Twenty-eight AFMs carried the mutation (C9+). Participants had up to 3 magnetic resonance imaging (MRI) scans, after which we compared motor cortex and motor tracts between C9+ and C9- AFMs using mixed effects models, incorporating kinship to correct for familial relations and lessen effects of other genetic factors. We also compared cortical, subcortical, cerebellar, and connectome structural measurements in a hypothesis-free analysis. We correlated regional C9orf72 expression in donor brains with the pattern of cortical thinning in C9+ AFMs using meta-regression. For comparison, we included 42 C9+ and 439 C9- patients with amyotrophic lateral sclerosis (ALS) in this analysis. C9+ AFM motor cortex had less gyrification and was thinner than in C9- AFMs, without differences in motor tracts. Whole brain analysis revealed thinner cortex and less gyrification in parietal, occipital, and temporal regions, smaller thalami and right hippocampus, and affected frontotemporal connections. Thinning of bilateral precentral, precuneus, and left superior parietal cortex was faster in C9+ than in C9- AFMs. Higher C9orf72 expression correlated with thinner cortex in both C9+ AFMs and C9+ ALS patients. In asymptomatic C9orf72 repeat expansion carriers, brain MRI reveals widespread features suggestive of impaired neurodevelopment, along with faster decline of motor and parietal cortex than found in normal aging. C9orf72 expression might play a role in cortical development, and consequently explain the specific brain abnormalities of mutation carriers. ANN NEUROL 2023;93:668-680.

Meningeal defects and focal cortical dysplasia: an unrecognized relationship? Illustrative case.

BACKGROUNDFocal cortical dysplasias (FCDs) are a heterogenous cluster of histopathologic entities classically associated with medically refractory epilepsy. Because there is substantial histopathologic variation among different types of FCD, there are likely multiple pathogenic mechanisms leading to these disorders. The meninges are known to play a role in cortical development, and disruption of meningeal-derived signaling pathways has been shown to impact neurodevelopment. To our knowledge, there has not yet been an investigation into whether genetic pathways regulating meningeal development may be involved in the development of FCD.OBSERVATIONSThe authors reported a patient with refractory epilepsy and evidence of FCD on imaging who received surgical intervention and was found to have an unusual dural anomaly overlying a region of type Ic FCD. To the authors’ knowledge, this was the first report describing a lesion of this nature in the context of FCD.LESSONSThe dural anomaly exhibited by the patient presented what could be a potentially novel pathogenic mechanism of FCD. Resection of the cortical tissue underlying the dural anomaly resulted in improvement in seizure control. Although the pathogenesis is unclear, this case highlighted the importance of further investigation into the developmental origins of FCD, which may help elucidate whether a connection between meningeal development and FCD exists.

Meis1 plays roles in cortical development through regulation of cellular proliferative capacity in the embryonic cerebrum.

Meis1 (myeloid ecotropic insertion site 1) is known to be related to embryonic development and cancer. In this study, to analyze the function of Meis1 in neural stem cells, we crossed Meis1fl/fl (Meis1 floxed) mice with Nestin-Cre mice. The results showed that Meis1-conditional knockout mice showed cerebral cortex malformation. The mice had a significantly thinner cortex than wildtype mice. At E14.5, BrdU incorporation and Pax6-positive radial glial cells were significantly decreased in the cerebral cortex of Meis1 knockout embryos as compared with wild-type embryos, whereas Tbr2-positive intermediate progenitors and NeuN-positive differentiated neurons were not. Cell death detected by immunostaining with cleaved caspase3 antibody showed no difference in the cortex between knockout and wild-type embryos. Furthermore, knockout of Meis1 in embryo by in utero electroporation showed that cellular migration was disturbed during cortical development. Therefore, Meis1 could play important roles during cortical development through the regulation of cell proliferation and migration in the embryonic cerebral cortex.

Neonatal Isoflurane Does Not Affect Sleep Architecture and Minimally Alters Neuronal Beta Oscillations in Adolescent Rats.

General anesthetics are neurotoxic to the developing rodent and primate brains leading to neurocognitive and socio-affective impairment later in life. In addition, sleep patterns are important predictors of cognitive outcomes. Yet, little is known about how anesthetics affect sleep-wake behaviors and their corresponding oscillations. Here we examine how neonatal general anesthesia affects sleep and wake behavior and associated neuronal oscillations. We exposed male and female rat pups to either 6 h of continuous isoflurane or sham anesthesia (compressed air) at the peak of their brain development (postnatal day 7). One cohort of animals was used to examine neurotoxic insult 2 h post-anesthesia exposure. At weaning age, a second cohort of rats was implanted with cortical electroencephalogram electrodes and allowed to recover. During adolescence, we measured sleep architecture (divided into wake, non-rapid eye movement, and rapid eye movement sleep) and electroencephalogram power spectra over a 24 h period. We found that exposure to neonatal isoflurane caused extensive neurotoxicity but did not disrupt sleep architecture in adolescent rats. However, these animals had a small but significant reduction in beta oscillations, specifically in the 12–20 Hz beta 1 range, associated with wake behavior. Furthermore, beta oscillations play a critical role in cortical development, cognitive processing, and homeostatic sleep drive. We speculate that dysregulation of beta oscillations may be implicated in cognitive and socio-affective outcomes associated with neonatal anesthesia.

In silico analysis of glycosylation pattern in 5th-6th repeat sequence of reelin glycoprotein

Reelin is an extracellular matrix glycoprotein that plays a key role in cortical development, maturation, synaptic plasticity, and memory formation in the adult mammalian brain. Glycosylation is a significant post- and co-translational modification of proteins. Although glycosylation contributes to the characteristic of proteins from their production to molecular interactions, the knowledge about the glycosylation pattern of reelin is very limited. In this study, we aimed to predict the potential glycosylation pattern of the 5th-6th repeat of central reelin fragment that responsible for their signaling, by using in silico methods. We found that the predicted glycosylation pattern of the 5th-6th repeat of human reelin was highly conserved between vertebrate species. However, this conservation was not observed in analyzed invertebrates. For the first time, we described the sites of glycosylation at a three-dimensional protein structure in human reelin. Because the sites were very closed to EGF-like repeats and receptor binding sites, they could contribute the interaction with a partner of reelin in addition to the effect of thermostability to protein. Many of the residues related glycosylation were also conserved in analyzed species. These findings may guide biochemical, genetic, and glycobiology base on further experiments about reelin glycosylation. The understanding of reelin glycosylation might change the point of view of treatment for many pathological conditions in neurodegenerative diseases such as Alzheimer’s disease. Communicated by Ramaswamy H. Sarma

Macromolecule suppressed GABA levels show no relationship with age in a pediatric sample

The inhibitory neurotransmitter γ-Aminobutyric acid (GABA) plays a crucial role in cortical development. Therefore, characterizing changes in GABA levels during development has important implications for the study of healthy development and developmental disorders. Brain GABA levels can be measured non-invasively using GABA-edited magnetic resonance spectroscopy (MRS). However, the most commonly used editing technique to measure GABA results in contamination of the GABA signal with macromolecules (MM). Therefore, GABA measured using this technique is often referred to as GABA+ . While few in number, previous studies have shown GABA+ levels increase with age during development. However, these studies are unable to specify whether it is specifically GABA that is increasing or, instead, if levels of MM increase. In this study, we use a GABA-editing technique specifically designed to suppress the MM signal (MM-supp GABA). We find no relationship between MM-supp GABA and age in healthy children aged 7–14 years. These findings suggest that the relationship between GABA+ and age is driven by changes in MM levels, not by changes in GABA levels. Moreover, these findings highlight the importance of accounting for MM levels in MRS quantification.

Assessment of radial glia in the frontal lobe of fetuses with Down syndrome

Down syndrome (DS) occurs with triplication of human chromosome 21 and is associated with deviations in cortical development evidenced by simplified gyral appearance and reduced cortical surface area. Radial glia are neuronal and glial progenitors that also create a scaffolding structure essential for migrating neurons to reach cortical targets and therefore play a critical role in cortical development. The aim of this study was to characterise radial glial expression pattern and morphology in the frontal lobe of the developing human fetal brain with DS and age-matched controls. Secondly, we investigated whether microstructural information from in vivo magnetic resonance imaging (MRI) could reflect histological findings from human brain tissue samples. Immunohistochemistry was performed on paraffin-embedded human post-mortem brain tissue from nine fetuses and neonates with DS (15–39 gestational weeks (GW)) and nine euploid age-matched brains (18–39 GW). Radial glia markers CRYAB, HOPX, SOX2, GFAP and Vimentin were assessed in the Ventricular Zone, Subventricular Zone and Intermediate Zone. In vivo diffusion MRI was used to assess microstructure in these regions in one DS (21 GW) and one control (22 GW) fetal brain. We found a significant reduction in radial glial progenitor SOX2 and subtle deviations in radial glia expression (GFAP and Vimentin) prior to 24 GW in DS. In vivo, fetal MRI demonstrates underlying radial projections consistent with immunohistopathology. Radial glial alterations may contribute to the subsequent simplified gyral patterns and decreased cortical volumes observed in the DS brain. Recent advances in fetal MRI acquisition and analysis could provide non-invasive imaging-based biomarkers of early developmental deviations.

NCAM2 Regulates Dendritic and Axonal Differentiation through the Cytoskeletal Proteins MAP2 and 14-3-3.

Neural cell adhesion molecule 2 (NCAM2) is involved in the development and plasticity of the olfactory system. Genetic data have implicated the NCAM2 gene in neurodevelopmental disorders including Down syndrome and autism, although its role in cortical development is unknown. Here, we show that while overexpression of NCAM2 in hippocampal neurons leads to minor alterations, its downregulation severely compromises dendritic architecture, leading to an aberrant phenotype including shorter dendritic trees, retraction of dendrites, and emergence of numerous somatic neurites. Further, our data reveal alterations in the axonal tree and deficits in neuronal polarization. In vivo studies confirm the phenotype and reveal an unexpected role for NCAM2 in cortical migration. Proteomic and cell biology experiments show that NCAM2 molecules exert their functions through a protein complex with the cytoskeletal-associated proteins MAP2 and 14-3-3γ and ζ. We provide evidence that NCAM2 depletion results in destabilization of the microtubular network and reduced MAP2 signal. Our results demonstrate a role for NCAM2 in dendritic formation and maintenance, and in neural polarization and migration, through interaction of NCAM2 with microtubule-associated proteins.

Evolutionary Gain of Dbx1 Expression Drives Subplate Identity in the Cerebral Cortex

Changes in transcriptional regulation through cis-regulatory elements are thought to drive brain evolution. However, how this impacts the identity ofprimate cortical neurons is still unresolved. Here,we show that primate-specific cis-regulatory sequences upstream of the Dbx1 gene promote human-like expression in the mouse embryonic cerebral cortex, and this imparts cell identity. Indeed, while Dbx1 is expressed in highly restricted cortical progenitors in the mouse ventral pallium, it is maintained in neurons in primates. Phenocopy of the primate-like Dbx1 expression in mouse cortical progenitors induces ectopic Cajal-Retzius and subplate (SP) neurons, which are transient populations playing crucial roles in cortical development. A conditional expression solely in neurons uncouples mitotic and postmitotic activities of Dbx1 and exclusively promotes a SP-like fate. Our results highlight how transcriptional changes of a single fate determinant in postmitotic cells may contribute to the expansion of neuronal diversity during cortical evolution.

Polymicrogyria associated with 17p13.3p13.2 duplication: Case report and review of the literature

We present the case of a male infant with bilateral perisylvian polymicrogyria associated with a de novo duplication of chromosome region 17p13.3p13.2. To our knowledge, this is the first report of polymicrogyria associated with the 17p13.3 contiguous gene duplication syndrome. Testing for known monogenic causes of polymicrogyria was negative and there was no clinical evidence of an acquired prenatal cause. Given the critical, dose-sensitive role that the 17p13.3 region plays in brain development, we suggest that the chromosome duplication is the most likely explanation for the polymicrogyria. Clinical and functional studies have demonstrated deleterious effects of increased LIS1 expression on the developing brain and the contribution of YWHAE to the brain phenotype of the 17p13 duplication syndrome. There is also evidence that CRK, the other candidate gene in this region, via interaction with LIS1, plays a critical role in cortical development. In addition to LIS1, YWHAE and CRK, our patient's chromosome duplication involves at least 100 other genes, less than half of which are annotated at the time of writing. It is expected that the ongoing use of chromosome microarray and next-generation sequencing to investigate the genetic causes of brain malformations will continue to extend our understanding of the 17p13 region and of the contributions of the genes in this region to cortical development.

FOXP2 exhibits projection neuron class specific expression, but is not required for multiple aspects of cortical histogenesis.

The expression patterns of the transcription factor FOXP2 in the developing mammalian forebrain have been described, and some studies have tested the role of this protein in the development and function of specific forebrain circuits by diverse methods and in multiple species. Clinically, mutations in FOXP2 are associated with severe developmental speech disturbances, and molecular studies indicate that impairment of Foxp2 may lead to dysregulation of genes involved in forebrain histogenesis. Here, anatomical and molecular phenotypes of the cortical neuron populations that express FOXP2 were characterized in mice. Additionally, Foxp2 was removed from the developing mouse cortex at different prenatal ages using two Cre-recombinase driver lines. Detailed molecular and circuit analyses were undertaken to identify potential disruptions of development. Surprisingly, the results demonstrate that Foxp2 function is not required for many functions that it has been proposed to regulate, and therefore plays a more limited role in cortical development than previously thought.

Layer-specific involvement of endocannabinoid signaling in muscarinic-induced long-term depression in layer 2/3 pyramidal neurons of rat visual cortex

Neuromodulatory facilitation of long-term synaptic plasticity is important in learning, memory, and experience-dependent cortical plasticity. Although muscarinic-induced long-term depression (mLTD) in the visual cortex is well known, its cellular mechanisms are not fully understood yet. Since endocannabinoid signaling mediates presynaptic expression of LTD in various brain areas including the primary visual cortex of rats, we investigated the involvement of endocannabinoids in the induction of mLTD in different dendritic compartments of layer 2/3 pyramidal neurons. With an unloading experiment of FM1-43 as an indicator of synaptic vesicle recycling, we confirmed that layer 1 and layer 4 stimulations mainly activated distal apical (in layer 1) and perisomatic (in layer 2/3) dendritic compartments, respectively. Bath application of muscarine (10 min) induced LTD in synaptic inputs activated by stimulation of layers 1 (L1-mLTD) and 4 (L2/3-mLTD). Both mLTDs were blocked by intracellular Ca2+ chelator BAPTA and bath application of NMDA receptor antagonist d-AP5. However, only L2/3-mLTD exhibited an increase in paired-pulse ratio. In addition, only L2/3-mLTD was blocked by treatment with CB1 receptor antagonist AM251. Both mLTDs were blocked by intracellular NMDA receptor antagonist MK801, but not by glia-specific metabolic inhibitor fluoroacetate, implying that neither presynaptic NMDA receptors nor astrocytes are involved in mLTD. These results suggest that L2/3-mLTD is expressed presynaptically via retrograde endocannabinoid signaling while L1-mLTD is endocannabinoid independent in layer 2/3 pyramidal neurons of the visual cortex. Therefore, layer-specific involvement of endocannabinoids in the induction of mLTD might play an important role in cortical development and information processing in the neocortex.

Cenpj Regulates Cilia Disassembly and Neurogenesis in the Developing Mouse Cortex.

Primary cilia are microtubule-based protuberances that project from the eukaryotic cell body to sense the extracellular environment. Ciliogenesis is closely correlated to the cell cycle and defects of cilia are related to human systemic diseases such as primary ciliary dyskinesia. However, the role of ciliogenesis in cortical development remains unclear. Here, we demonstrate that Cenpj, a protein that is required for centriole biogenesis, plays a role in regulating cilium disassembly in vivo Depletion of Cenpj in neural progenitor cells results in long cilia and abnormal cilia disassembly. Radial glial cells Cenpj depletion exhibit uncompleted cell division, reduced cell proliferation, and increased cell apoptosis in the developing mouse cerebrum cortex, leading to microcephaly. In addition, Cenpj depletion causes long and thin primary cilia and motile cilia in adult neural stem cells and reduced cell proliferation in the subventricular zone. Furthermore, we show that Cenpj regulates cilia disassembly and neurogenesis through Kif2a, a plus-end-directed motor protein. These data collected from mice of both sexes provide insights into how ciliogenesis plays roles in cortical development and how primary microcephaly is induced by Cenpj mutations in humans.SIGNIFICANCE STATEMENT Autosomal recessive primary microcephaly is a neurodevelopmental disorder with the major symptoms of reduction of circumference of the head, brain volume, and cortex thickness with normal brain architecture in birth. We used conditional Cenpj deletion mice and found that neural progenitor cells (NPCs) exhibited long primary cilia and abnormal cilium appendages. The defective cilium disassembly caused by Cenpj depletion might correlate to reduced cell proliferation, uncompleted cell division, cell apoptosis, and microcephaly in mice. Cenpj also regulates the cilium structure of adult neural stem cells and adult neurogenesis in mice. Additionally, our results illustrate that Cenpj regulates cilia disassembly and neurogenesis through Kif2a, indicating that primary cilia dynamics play a crucial role in NPC mitosis and adult neurogenesis.

Proteomic analysis of FOXP proteins reveals interactions between cortical transcription factors associated with neurodevelopmental disorders.

FOXP transcription factors play important roles in neurodevelopment, but little is known about how their transcriptional activity is regulated. FOXP proteins cooperatively regulate gene expression by forming homo- and hetero-dimers with each other. Physical associations with other transcription factors might also modulate the functions of FOXP proteins. However, few FOXP-interacting transcription factors have been identified so far. Therefore, we sought to discover additional transcription factors that interact with the brain-expressed FOXP proteins, FOXP1, FOXP2 and FOXP4, through affinity-purifications of protein complexes followed by mass spectrometry. We identified seven novel FOXP-interacting transcription factors (NR2F1, NR2F2, SATB1, SATB2, SOX5, YY1 and ZMYM2), five of which have well-estabslished roles in cortical development. Accordingly, we found that these transcription factors are co-expressed with FoxP2 in the deep layers of the cerebral cortex and also in the Purkinje cells of the cerebellum, suggesting that they may cooperate with the FoxPs to regulate neural gene expression in vivo. Moreover, we demonstrated that etiological mutations of FOXP1 and FOXP2, known to cause neurodevelopmental disorders, severely disrupted the interactions with FOXP-interacting transcription factors. Additionally, we pinpointed specific regions within FOXP2 sequence involved in mediating these interactions. Thus, by expanding the FOXP interactome we have uncovered part of a broader neural transcription factor network involved in cortical development, providing novel molecular insights into the transcriptional architecture underlying brain development and neurodevelopmental disorders.

In Vitro Effects of Wistar Rat Prenatal and Postnatal Cerebrospinal Fluid on Neural Differentiation and P roliferation of Mesenchymal Stromal Cells Derived from Bone Marrow.

Objective Cerebrospinal fluid (CSF) plays an important role in cortical development during the fetal stages. Embryonic CSF (E-CSF) consists of numerous neurotrophic and growth factors that regulate neurogenesis, differentiation, and proliferation. Mesenchymal stem cells (MSCs) are multi-potential stem cells that can differentiate into mesenchymal and non-mesenchymal cells, including neural cells. This study evaluates the prenatal and postnatal effects of CSF on proliferation and neural differentiation of bone marrow MSCs (BM-MSCs) at gestational ages E19, E20, and the first day after birth (P1). Materials and Methods In this experimental study, we confirmed the mesenchymal nature of BM-MSCs according to their adherence properties and surface markers (CD44, CD73 and CD45). The multi-potential characteristics of BM- MSCs were verified by assessments of the osteogenic and adipogenic potentials of these cells. Under appropriate in vitro conditions, the BM-MSCs cultures were incubated with and without additional pre- and postnatal CSF. The MTT assay was used to quantify cellular proliferation and viability. Immunocytochemistry was used to study the expression of MAP-2 and β-III tubulin in the BM-MSCs. We used ImageJ software to measure the length of the neurites in the cultured cells. Results BM-MSCs differentiated into neuronal cell types when exposed to basic fibroblast growth factor (b-FGF). Viability and proliferation of the BM-MSCs conditioned with E19, E20, and P1 CSF increased compared to the control group. We observed significantly elevated neural differentiation of the BM-MSCS cultured in the CSF-supplemented medium from E19 compared to cultures conditioned with E20 and P1 CSF group. ConclusionThe results have confirmed that E19, E20, and P1 CSF could induce proliferation and differentiation of BM-MSCs though they are age dependent factors. The presented data support a significant, conductive role of CSF components in neuronal survival, proliferation, and differentiation.

Unique spatiotemporal requirements for intraflagellar transport genes during forebrain development

Primary cilia are organelles extended from virtually all cells and are required for the proper regulation of a number of canonical developmental pathways. The role in cortical development of proteins important for ciliary form and function is a relatively understudied area. Here we have taken a genetic approach to define the role in forebrain development of three intraflagellar transport proteins known to be important for primary cilia function. We have genetically ablated Kif3a, Ift88, and Ttc21b in a series of specific spatiotemporal domains. The resulting phenotypes allow us to draw several conclusions. First, we conclude that the Ttc21b cortical phenotype is not due to the activity of Ttc21b within the brain itself. Secondly, some of the most striking phenotypes are from ablations in the neural crest cells and the adjacent surface ectoderm indicating that cilia transduce critical tissue—tissue interactions in the developing embryonic head. Finally, we note striking differences in phenotypes from ablations only one embryonic day apart, indicating very discrete spatiotemporal requirements for these three genes in cortical development.