A Novel c-Jun N-terminal Kinase (JNK) Signaling Complex Involved in Neuronal Migration during Brain Development

Puckered and JNK signaling in pioneer neurons coordinates the motor activity of the Drosophila embryo

Central nervous system organogenesis is a complex process that obeys precise architectural rules. The impact that nervous system architecture may have on its functionality remains, however, relatively unexplored. To clarify this problem, we analyze the development of the Drosophila embryonic Ventral Nerve Cord (VNC). VNC morphogenesis requires the tight control of Jun kinase (JNK) signaling in a subset of pioneer neurons, exerted in part via a negative feedback loop mediated by the dual specificity phosphatase Puckered. Here we show that the JNK pathway autonomously regulates neuronal electrophysiological properties without affecting synaptic vesicle transport. Manipulating JNK signaling activity in pioneer neurons during early embryogenesis directly influences their function as organizers of VNC architecture and, moreover, uncovers a role in the coordination of the embryonic motor circuitry that is required for hatching. Together, our data reveal critical links, mediated by the control of the JNK signaling cascade by Puckered, between the structural organization of the VNC and its functional optimization.

Interneuron odyssey: molecular mechanisms of tangential migration

Cortical GABAergic interneurons are critical components of neural networks. They provide local and long-range inhibition and help coordinate network activities involved in various brain functions, including signal processing, learning, memory and adaptative responses. Disruption of cortical GABAergic interneuron migration thus induces profound deficits in neural network organization and function, and results in a variety of neurodevelopmental and neuropsychiatric disorders including epilepsy, intellectual disability, autism spectrum disorders and schizophrenia. It is thus of paramount importance to elucidate the specific mechanisms that govern the migration of interneurons to clarify some of the underlying disease mechanisms. GABAergic interneurons destined to populate the cortex arise from multipotent ventral progenitor cells located in the ganglionic eminences and pre-optic area. Post-mitotic interneurons exit their place of origin in the ventral forebrain and migrate dorsally using defined migratory streams to reach the cortical plate, which they enter through radial migration before dispersing to settle in their final laminar allocation. While migrating, cortical interneurons constantly change their morphology through the dynamic remodeling of actomyosin and microtubule cytoskeleton as they detect and integrate extracellular guidance cues generated by neuronal and non-neuronal sources distributed along their migratory routes. These processes ensure proper distribution of GABAergic interneurons across cortical areas and lamina, supporting the development of adequate network connectivity and brain function. This short review summarizes current knowledge on the cellular and molecular mechanisms controlling cortical GABAergic interneuron migration, with a focus on tangential migration, and addresses potential avenues for cell-based interneuron progenitor transplants in the treatment of neurodevelopmental disorders and epilepsy.

Development of an Adverse Outcome Pathway for radiation-induced microcephaly via expert consultation and machine learning

BACKGROUND

Brain development during embryogenesis and in early postnatal life is particularly complex and involves the interplay of many cellular processes and molecular mechanisms, making it extremely vulnerable to exogenous insults, including ionizing radiation (IR). Microcephaly is one of the most frequent neurodevelopmental abnormalities that is characterized by small brain size, and is often associated with intellectual deficiency. Decades of research span from epidemiological data on in utero exposure of the A-bomb survivors, to studies on animal and cellular models that allowed deciphering the most prominent molecular mechanisms leading to microcephaly. The Adverse Outcome Pathway (AOP) framework is used to organize, evaluate and portray the scientific knowledge of toxicological effects spanning different biological levels of organizations, from the initial interaction with molecular targets to the occurrence of a disease or adversity. In the present study, the framework was used in an attempt to organize the current scientific knowledge on microcephaly progression in the context of ionizing radiation (IR) exposure. This work was performed by a group of experts formed during a recent workshop organized jointly by the Multidisciplinary European Low Dose Initiative (MELODI) and the European Radioecology Alliance (ALLIANCE) associations to present the AOP approach and tools. Here we report on the development of a putative AOP for congenital microcephaly resulting from IR exposure based on discussions of the working group and we emphasize the use of a novel machine-learning approach to assist in the screening of the available literature to develop AOPs.

CONCLUSION

The expert consultation led to the identification of crucial biological events for the progression of microcephaly upon exposure to IR, and highlighted current knowledge gaps. The machine learning approach was successfully used to screen the existing knowledge and helped to rapidly screen the body of evidence and in particular the epidemiological data. This systematic review approach also ensured that the analysis was sufficiently comprehensive to identify the most relevant data and facilitate rapid and consistent AOP development. We anticipate that as machine learning approaches become more user-friendly through easy-to-use web interface, this would allow AOP development to become more efficient and less time consuming.

Protective effects of berberine on various kidney diseases: Emphasis on the promising effects and the underlined molecular mechanisms

Berberine (BBR) is a pentacyclic benzylisoquinoline alkaloid that can be found in diversity of medicinal plants. BBR has a wide range of pharmacological bioactivities, in addition when administrated orally, it has a broad safety margin. It has been used as an antidiarrheal, antimicrobial, and anti-diabetic drug in Ayurvedic and Chinese medicine. Several scholars have found that BBR has promising renoprotective effects against different renal illnesses, including diabetic nephropathy, renal fibrosis, renal ischemia, renal aging, and renal stones. Also, it has renoprotective effects against nephrotoxicity induced by chemotherapy, heavy metal, aminoglycosides, NSAID, and others. These effects imply that BBR has an evolving therapeutic potential against acute renal failure and chronic renal diseases. Hence, we report herein the beneficial therapeutic renoprotective properties of BBR, as well as the highlighted molecular mechanism. In conclusion, the studies discussed throughout this review will afford a comprehensive overview about renoprotective effect of BBR and its therapeutic impact on different renal diseases.

Paeoniflorin attenuates monocrotaline-induced pulmonary arterial hypertension in rats by suppressing TAK1-MAPK/NF-κB pathways

Pulmonary arterial hypertension (PAH) characterized by pulmonary vascular remodeling is a lethal disease. Paeoniflorin (PF) is a monoterpene glycoside with numerous beneficial functions, such as vasodilation, anti-inflammation and immunomodulation. This study aims to investigate the effects of PF on monocrotaline (MCT)-induced PAH rats. Our data showed that both prophylactic or therapeutic administration of PF alleviated MCT-induced increasing of right ventricular systolic pressure (RVSP), prevented right ventricle hypertrophy and pulmonary arterial remodeling, as well as inhibited inflammatory cell infiltration around pulmonary arteries. Meanwhile, PF blocked MCT-induced endothelial-mesenchymal transition (EndMT) as indicated by the restored expression of endothelial markers in lung. Moreover, PF inhibited MCT-induced down-regulation of bone morphogenetic protein receptor 2 (BMPR2) and suppressed MCT-induced phosphorylation of transforming growth factor-β (TGFβ) activated kinase 1 (TAK1) in vivo. In vitro studies indicated that PF prevented human pulmonary arterial smooth muscle cells (PASMCs) from platelet-derived growth factor-BB (PDGF-BB)-stimulated proliferation and migration. PF also partially reversed TGFβ1, interleukin-1β (IL-1β) and tumor necrosis factor (TNF-α) co-stimulated endothelial-to-mesenchymal transition (EndMT) in cultured human pulmonary artery endothelial cells (HPAECs). Signaling pathway analysis demonstrated that the underlying mechanism might be associated with the inhibition of TAK1-MAPK/NF-κB pathways. Taken together, our results suggested that PF could be a potential drug for the treatment of PAH.

Dysregulated miR-29a-3p/PMP22 Modulates Schwann Cell Proliferation and Migration During Peripheral Nerve Regeneration

Schwann cells switch to a repair phenotype following peripheral nerve injury and create a favorable microenvironment to drive nerve repair. Many microRNAs (miRNAs) are differentially expressed in the injured peripheral nerves and play essential roles in regulating Schwann cell behaviors. Here, we examine the temporal expression patterns of miR-29a-3p after peripheral nerve injury and demonstrate significant up-regulation of miR-29a-3p in injured sciatic nerves. Elevated miR-29a-3p inhibits Schwann cell proliferation and migration, while suppressed miR-29a-3p executes reverse effects. In vivo injection of miR-29a-3p agomir to rat sciatic nerves hinders the proliferation and migration of Schwann cells, delays the elongation and myelination of axons, and retards the functional recovery of injured nerves. Mechanistically, miR-29a-3p modulates Schwann cell activities via negatively regulating peripheral myelin protein 22 (PMP22), and PMP22 extensively affects Schwann cell metabolism. Our results disclose the vital role of miR-29a-3p/PMP22 in regulating Schwann cell phenotype following sciatic nerve injury and shed light on the mechanistic basis of peripheral nerve regeneration.

Cytoskeleton and Associated Proteins: Pleiotropic JNK Substrates and Regulators

This review extensively reports data from the literature concerning the complex relationships between the stress-induced c-Jun N-terminal kinases (JNKs) and the four main cytoskeleton elements, which are actin filaments, microtubules, intermediate filaments, and septins. To a lesser extent, we also focused on the two membrane-associated cytoskeletons spectrin and ESCRT-III. We gather the mechanisms controlling cytoskeleton-associated JNK activation and the known cytoskeleton-related substrates directly phosphorylated by JNK. We also point out specific locations of the JNK upstream regulators at cytoskeletal components. We finally compile available techniques and tools that could allow a better characterization of the interplay between the different types of cytoskeleton filaments upon JNK-mediated stress and during development. This overview may bring new important information for applied medical research.

Pathophysiological Significance of WDR62 and JNK Signaling in Human Diseases

The c-Jun N-terminal kinase (JNK) is highly evolutionarily conserved and plays important roles in a broad range of physiological and pathological processes. The WD40-repeat protein 62 (WDR62) is a scaffold protein that recruits different components of the JNK signaling pathway to regulate several human diseases including neurological disorders, infertility, and tumorigenesis. Recent studies revealed that WDR62 regulates the process of neural stem cell mitosis and germ cell meiosis through JNK signaling. In this review we summarize the roles of WDR62 and JNK signaling in neuronal and non-neuronal contexts and discuss how JNK-dependent signaling regulates both processes. WDR62 is involved in various human disorders via JNK signaling regulation, and may represent a promising therapeutic strategy for the treatment of related diseases.

SRPS associated protein WDR60 regulates the multipolar-to-bipolar transition of migrating neurons during cortical development

Mutations of WD40 repeat domain 60 (WDR60) have been identified in short-rib polydactyly syndromes (SRPS I–V), a group of lethal congenital disorders characterized by short ribs, polydactyly, and a range of extraskeletal phenotypes. However, the underlying mechanism is still unclear. Here, we report that WDR60 is essential for embryonic development and plays a critical role in the multipolar-bipolar transition and migration of newborn neurons during brain development. Mechanically, we found that WDR60 was located at the microtubule-organizing center to control microtubule organization and possibly, the trafficking of cellular components. Importantly, the migration defect caused by Wdr60 knockdown could be rescued by the stable form of α-Tubulin, α-Tubulin^K40Q (an acetylation-mimicking mutant). These findings identified a non-cilia function of WDR60 and provided insight into its biological function, as well as the pathogenesis of WDR60 deficiency associated with SRPS.

Maternal folic acid impacts DNA methylation profile in male rat offspring implicated in neurodevelopment and learning/memory abilities

Background

Periconceptional folic acid (FA) supplementation not only reduces the incidence of neural tube defects, but also improves cognitive performances in offspring. However, the genes or pathways that are epigenetically regulated by FA in neurodevelopment were rarely reported.

Methods

To elucidate the underlying mechanism, the effect of FA on the methylation profiles in brain tissue of male rat offspring was assessed by methylated DNA immunoprecipitation chip. Differentially methylated genes (DMGs) and gene network analysis were identified using DAVID and KEGG pathway analysis.

Results

Compared with the folate-normal diet group, 1939 DMGs were identified in the folate-deficient diet group, and 1498 DMGs were identified in the folate-supplemented diet group, among which 298 DMGs were overlapped. The pathways associated with neurodevelopment and learning/memory abilities were differentially methylated in response to maternal FA intake during pregnancy, and there were some identical and distinctive potential mechanisms under FA deficiency or FA-supplemented conditions.

Conclusions

In conclusion, genes and pathways associated with neurodevelopment and learning/memory abilities were differentially methylated in male rat offspring in response to maternal FA deficiency or supplementation during pregnancy.

c-Jun N-Terminal Kinase Inhibitors as Potential Leads for New Therapeutics for Alzheimer's Diseases

Alzheimer's Disease (AD) is becoming more prevalent as the population lives longer. For individuals over 60 years of age, the prevalence of AD is estimated at 40.19% across the world. Regarding the cognitive decline caused by the disease, mitogen-activated protein kinases (MAPK) pathways such as the c-Jun N-terminal kinase (JNK) pathway are involved in the progressive loss of neurons and synapses, brain atrophy, and augmentation of the brain ventricles, being activated by synaptic dysfunction, oxidative stress, and excitotoxicity. Nowadays, AD symptoms are manageable, but the disease itself remains incurable, thus the inhibition of JNK3 has been explored as a possible therapeutic target, considering that JNK is best known for its involvement in propagating pro-apoptotic signals. This review aims to present biological aspects of JNK, focusing on JNK3 and how it relates to AD. It was also explored the recent development of inhibitors that could be used in AD treatment since several drugs/compounds in phase III clinical trials failed. General aspects of the MAPK family, therapeutic targets, and experimental treatment in models are described and discussed throughout this review.

JNK Signaling Regulates Cellular Mechanics of Cortical Interneuron Migration

Aberrant migration of inhibitory interneurons can alter the formation of cortical circuitry and lead to severe neurologic disorders including epilepsy, autism, and schizophrenia. However, mechanisms involved in directing the migration of interneurons remain incompletely understood. Using a mouse model, we performed live-cell confocal microscopy to explore the mechanisms by which the c-Jun NH₂-terminal kinase (JNK) pathway coordinates leading process branching and nucleokinesis, two cell biological processes that are essential for the guided migration of cortical interneurons. Pharmacological inhibition of JNK signaling disrupts the kinetics of leading process branching, rate and amplitude of nucleokinesis, and leads to the rearward mislocalization of the centrosome and primary cilium to the trailing process. Genetic loss of Jnk from interneurons also impairs leading process branching and nucleokinesis, suggesting that important mechanics of interneuron migration depend on the intrinsic activity of JNK. These findings highlight key roles for JNK signaling in leading process branching, nucleokinesis, and the trafficking of centrosomes and cilia during interneuron migration, and further implicates JNK signaling as an important mediator of cortical development.

Molecular mechanisms of cell polarity in a range of model systems and in migrating neurons

Cell polarity is defined as the asymmetric distribution of cellular components along an axis. Most cells, from the simplest single-cell organisms to highly specialized mammalian cells, are polarized and use similar mechanisms to generate and maintain polarity. Cell polarity is important for cells to migrate, form tissues, and coordinate activities. During development of the mammalian cerebral cortex, cell polarity is essential for neurogenesis and for the migration of newborn but as-yet undifferentiated neurons. These oriented migrations include both the radial migration of excitatory projection neurons and the tangential migration of inhibitory interneurons. In this review, I will first describe the development of the cerebral cortex, as revealed at the cellular level. I will then define the core molecular mechanisms - the Par/Crb/Scrib polarity complexes, small GTPases, the actin and microtubule cytoskeletons, and phosphoinositides/PI3K signaling - that are required for asymmetric cell division, apico-basal and front-rear polarity in model systems, including C elegans zygote, Drosophila embryos and cultured mammalian cells. As I go through each core mechanism I will explain what is known about its importance in radial and tangential migration in the developing mammalian cerebral cortex.

JNK signaling is required for proper tangential migration and laminar allocation of cortical interneurons

The precise migration of cortical interneurons is essential for the formation and function of cortical circuits, and disruptions to this key developmental process are implicated in the etiology of complex neurodevelopmental disorders, including schizophrenia, autism and epilepsy. We have recently identified the Jun N-terminal kinase (JNK) pathway as an important mediator of cortical interneuron migration in mice, regulating the proper timing of interneuron arrival into the cortical rudiment. In the current study, we demonstrate a vital role for JNK signaling at later stages of corticogenesis, when interneurons transition from tangential to radial modes of migration. Pharmacological inhibition of JNK signaling in ex vivo slice cultures caused cortical interneurons to rapidly depart from migratory streams and prematurely enter the cortical plate. Similarly, genetic loss of JNK function led to precocious stream departure ex vivo, and stream disruption, morphological changes and abnormal allocation of cortical interneurons in vivo These data suggest that JNK signaling facilitates the tangential migration and laminar deposition of cortical interneurons, and further implicates the JNK pathway as an important regulator of cortical development.

Crosstalk Between Signaling Pathways Involved in the Regulation of Airway Smooth Muscle Cell Hyperplasia

Increased ASM mass, primarily due to ASM hyperplasia, has been recognized as a hallmark of airway remodeling in asthma. Increased ASM mass is the major contributor to the airway narrowing, thus worsening the bronchoconstriction in response to stimuli. Inflammatory mediators and growth factors released during inflammation induce increased ASM mass surrounding airway wall via increased ASM proliferation, diminished ASM apoptosis and increased ASM migration. Several major pathways, such as MAPKs, PI3K/AKT, JAK2/STAT3 and Rho kinase, have been reported to regulate these cellular activities in ASM and were reported to be interrelated at certain points. This article aims to provide an overview of the signaling pathways/molecules involved in ASM hyperplasia as well as the mapping of the interplay/crosstalk between these major pathways in mediating ASM hyperplasia. A more comprehensive understanding of the complexity of cellular signaling in ASM cells will enable more specific and safer drug development in the control of asthma.

MKK7, the essential regulator of JNK signaling involved in cancer cell survival: a newly emerging anticancer therapeutic target

One of the mitogen-activated protein kinases (MAPKs), c-Jun NH2-terminal protein kinase (JNK) plays an important role in regulating cell fate, such as proliferation, differentiation, development, transformation, and apoptosis. Its activity is induced through the interaction of MAPK kinase kinases (MAP3Ks), MAPK kinases (MAP2Ks), and various scaffolding proteins. Because of the importance of the JNK cascade to intracellular bioactivity, many studies have been conducted to reveal its precise intracellular functions and mechanisms, but its regulatory mechanisms remain elusive. In this review, we discuss the molecular characterization, activation process, and physiological functions of mitogen-activated protein kinase kinase 7 (MKK7), the MAP2K that most specifically controls the activity of JNK. Understanding the role of MKK7/JNK signaling in physiological conditions could spark new hypotheses for targeted anticancer therapies.

Overlapping migratory mechanisms between neural progenitor cells and brain tumor stem cells

Neural stem cells present in the subventricular zone (SVZ), the largest neurogenic niche of the mammalian brain, are able to self-renew as well as generate neural progenitor cells (NPCs). NPCs are highly migratory and traverse the rostral migratory stream (RMS) to the olfactory bulb, where they terminally differentiate into mature interneurons. NPCs from the SVZ are some of the few cells in the CNS that migrate long distances during adulthood. The migratory process of NPCs is highly regulated by intracellular pathway activation and signaling from the surrounding microenvironment. It involves modulation of cell volume, cytoskeletal rearrangement, and isolation from compact extracellular matrix. In malignant brain tumors including high-grade gliomas, there are cells called brain tumor stem cells (BTSCs) with similar stem cell characteristics to NPCs but with uncontrolled cell proliferation and contribute to tumor initiation capacity, tumor progression, invasion, and tumor maintenance. These BTSCs are resistant to chemotherapy and radiotherapy, and their presence is believed to lead to tumor recurrence at distal sites from the original tumor location, principally due to their high migratory capacity. BTSCs are able to invade the brain parenchyma by utilizing many of the migratory mechanisms used by NPCs. However, they have an increased ability to infiltrate the tight brain parenchyma and utilize brain structures such as myelin tracts and blood vessels as migratory paths. In this article, we summarize recent findings on the mechanisms of cellular migration that overlap between NPCs and BTSCs. A better understanding of the intersection between NPCs and BTSCs will to provide a better comprehension of the BTSCs' invasive capacity and the molecular mechanisms that govern their migration and eventually lead to the development of new therapies to improve the prognosis of patients with malignant gliomas.

Spatiotemporal Regulation of Rho GTPases in Neuronal Migration

Neuronal migration is essential for the orchestration of brain development and involves several contiguous steps: interkinetic nuclear movement (INM), multipolar–bipolar transition, locomotion, and translocation. Growing evidence suggests that Rho GTPases, including RhoA, Rac, Cdc42, and the atypical Rnd members, play critical roles in neuronal migration by regulating both actin and microtubule cytoskeletal components. This review focuses on the spatiotemporal-specific regulation of Rho GTPases as well as their regulators and effectors in distinct steps during the neuronal migration process. Their roles in bridging extracellular signals and cytoskeletal dynamics to provide optimal structural support to the migrating neurons will also be discussed.

SGTb regulates a surface localization of a guidance receptor BOC to promote neurite outgrowth

Neuritogenesis is a critical event for neuronal differentiation and neuronal circuitry formation during neuronal development and regeneration. Our previous study revealed a critical role of a guidance receptor BOC in a neuronal differentiation and neurite outgrowth. However, regulatory mechanisms for BOC signaling pathway remain largely unexplored. In the current study, we have identified Small glutamine-rich tetratricopeptide repeat (TPR)-containing b (SGTb) as a BOC interacting protein through yeast two-hybrid screening. Like BOC, SGTb is highly expressed in brain and P19 embryonal carcinoma (EC) cells differentiated into neuronal cells. BOC and SGTb proteins co-precipitate in mouse brain and differentiated P19 EC cells. Furthermore, BOC and SGTb co-localize in neurites and especially are concentrated at the tip of neurites in various neuronal cells. SGTb depletion attenuates neuronal differentiation of P19 cells through reduction of the surface level of BOC. Additionally, SGTb depletion causes BOC localization at neurite tip, coinciding with decreased p-JNK levels critical for actin cytoskeleton remodeling. The overexpression of SGTb or BOC restores JNK activation in BOC or SGTb-depleted cells, respectively. Finally, SGTb elevates the level of surface-resident BOC in BOC-depleted cells, restoring JNK activation. Taken together, our data suggest that SGTb interacts with BOC and regulates its surface level and consequent JNK activation, thereby promoting neuronal differentiation and neurite outgrowth.

MEKK3 coordinates with FBW7 to regulate WDR62 stability and neurogenesis

Mutations of WD repeat domain 62 (WDR62) lead to autosomal recessive primary microcephaly (MCPH), and down-regulation of WDR62 expression causes the loss of neural progenitor cells (NPCs). However, how WDR62 is regulated and hence controls neurogenesis and brain size remains elusive. Here, we demonstrate that mitogen-activated protein kinase kinase kinase 3 (MEKK3) forms a complex with WDR62 to promote c-Jun N-terminal kinase (JNK) signaling synergistically in the control of neurogenesis. The deletion of Mekk3, Wdr62, or Jnk1 resulted in phenocopied defects, including premature NPC differentiation. We further showed that WDR62 protein is positively regulated by MEKK3 and JNK1 in the developing brain and that the defects of wdr62 deficiency can be rescued by the transgenic expression of JNK1. Meanwhile, WDR62 is also negatively regulated by T1053 phosphorylation, leading to the recruitment of F-box and WD repeat domain-containing protein 7 (FBW7) and proteasomal degradation. Our findings demonstrate that the coordinated reciprocal and bidirectional regulation among MEKK3, FBW7, WDR62, and JNK1, is required for fine-tuned JNK signaling for the control of balanced NPC self-renewal and differentiation during cortical development.

Microcephaly is a neural developmental disorder characterized by significantly reduced brain size and variable intellectual disability. WD repeat domain 62 (WDR62) was identified as the second most common gene for autosomal recessive primary microcephaly (MCPH) in human. Here, we studied the underlying regulatory mechanism of WDR62 and the impact on generation of new neurons. We show that mitogen-activated protein kinase kinase kinase 3 (Mekk3), Wdr62, and c-Jun N-terminal kinase 1 (Jnk1) knockout (KO) mice have defects in the generation and maturation of neurons. We demonstrate that WDR62 stability is positively regulated by a mitogen-activated protein kinase kinase kinase (MAPKKK), MEKK3, but negatively regulated by the E3 ligase, F-box and WD repeat domain-containing protein 7 (FBW7). These positive and negative factors calibrate the strength of the activity of the JNK signaling pathway, which controls self-renewal and differentiation of neural progenitor cells (NPCs) during brain development. This finding improves our understanding of the molecular pathogenesis of MCPH.

cTAGE5/MEA6 plays a critical role in neuronal cellular components trafficking and brain development

Normal neural development is essential for the formation of neuronal networks and brain function. Cutaneous T cell lymphoma-associated antigen 5 (cTAGE5)/meningioma expressed antigen 6 (MEA6) plays a critical role in the secretion of proteins. However, its roles in the transport of nonsecretory cellular components and in brain development remain unknown. Here, we show that cTAGE5/MEA6 is important for brain development and function. Conditional knockout of cTAGE5/MEA6 in the brain leads to severe defects in neural development, including deficits in dendrite outgrowth and branching, spine formation and maintenance, astrocyte activation, and abnormal behaviors. We reveal that loss of cTAGE5/MEA6 affects the interaction between the coat protein complex II (COPII) components, SAR1 and SEC23, leading to persistent activation of SAR1 and defects in COPII vesicle formation and transport from the endoplasmic reticulum to the Golgi, as well as disturbed trafficking of membrane components in neurons. These defects affect not only the transport of materials required for the development of dendrites and spines but also the signaling pathways required for neuronal development. Because mutations in cTAGE5/MEA6 have been found in patients with Fahr's disease, our study potentially also provides insight into the pathogenesis of this disorder.

WDR62 mediates TNFα-dependent JNK activation via TRAF2-MLK3 axis

The mitogen-activated protein kinases (MAPKs) regulate a variety of cellular processes. The three main MAPK cascades are the extracellular signal-regulated kinases (ERK), c-Jun N-terminal kinase (JNK), and p38 kinases. A typical MAPK cascade is composed of MAP3K-MAP2K-MAPK kinases that are held by scaffold proteins. Scaffolds function to assemble the protein tier and contribute to the specificity and efficacy of signal transmission. WD repeat domain 62 (WDR62) is a JNK scaffold protein, interacting with JNK, MKK7, and several MAP3Ks. The loss of WDR62 in human leads to microcephaly and pachygyria. Yet the role of WDR62 in cellular function is not fully studied. We used the CRISPR/Cas9 and short hairpin RNA approaches to establish a human breast cancer cell line MDA-MB-231 with WDR62 loss of function and studied the consequence to JNK signaling. In growing cells, WDR62 is responsible for the basal expression of c-Jun. In stressed cells, WDR62 specifically mediates TNFα-dependent JNK activation through the association with both the adaptor protein, TNF receptor-associated factor 2 (TRAF2), and the MAP3K protein, mixed lineage kinase 3. TNFα-dependent JNK activation is mediated by WDR62 in HCT116 and HeLa cell lines as well. MDA-MB-231 WDR62-knockout cells display increased resistance to TNFα-induced cell death. Collectively, WDR62 coordinates the TNFα receptor signaling pathway to JNK activation through association with multiple kinases and the adaptor protein TRAF2.

From Neural Crest Development to Cancer and Vice Versa: How p75NTR and (Pro)neurotrophins Could Act on Cell Migration and Invasion?

The p75 neurotrophin receptor (p75^NTR), also known as low-affinity nerve growth factor, belongs to the tumor necrosis factor family of receptors. p75^NTR is widely expressed in the nervous system during the development, as well as, in the neural crest population, since p75^NTR has been described as ubiquitously expressed and considered as a neural crest marker. Neural crest cells (NCCs) constitute an transient population accurately migrating and invading, with precision, defined sites of the embryo. During migration, NCCs are guided along distinct migratory pathways by specialized molecules present in the extracellular matrix or on the surfaces of those cells. Two main processes direct NCC migration during the development: (1) an epithelial-to-mesenchymal transition and (2) a process known as contact inhibition of locomotion. In adults, p75^NTR remains expressed by NCCs and has been identified in an increasing number of cancer cells. Nonetheless, the regulation of the expression of p75^NTR and the underlying mechanisms in stem cell biology or cancer cells have not yet been sufficiently addressed. The main objective of this review is therefore to analyze elements of our actual knowledge regarding p75^NTR roles during the development (mainly focusing on neural crest development) and see how we can transpose that information from development to cancer (and vice versa) to better understand the link between p75^NTR and cell migration and invasion. In this review, we successively analyzed the molecular mechanisms of p75^NTR when it interacts with several coreceptors and/or effectors. We then analyzed which signaling pathways are the most activated or linked to NCC migration during the development. Regarding cancer, we analyzed the described molecular pathways underlying cancer cell migration when p75^NTR was correlated to cancer cell migration and invasion. From those diverse sources of information, we finally summarized potential molecular mechanisms underlying p75^NTR activation in cell migration and invasion that could lead to new research areas to develop new therapeutic protocols.

Novel biomolecular information in rotenone-induced cellular model of Parkinson's disease

In order to uncover the remarkable pathogenic genes or molecular pathological process in Parkinson's disease (PD), we employed a microarray analysis upon the cellular PD model induced by rotenone. Compared to the control group, 2174 genes were screened out to be expressed differently in the rotenone-induced group by certain criterion. GO analysis and the pathways analysis showed the significant enrichment of genes that were associated with the biological process of cell cycle, apoptotic process, organelle fusion, mitochondrial lesion, endoplasmic reticulum stress and so on. Among these significant DE genes, some were sorted out to be involved in cell cycle and protein processing in endoplasmic reticulum. As the PPI network analysis showed, the interaction relationship of the DEGs involved in the process of protein generation in endoplasmic reticulum(ER) was clearly showed up. As a prediction, we emphasized the genes EDEM1, ATF4, TRAF2 might play central roles in the protein misfolding process during the progression of Parkinson's disease and these new-found genes might be the future research focus and therapeutic targets in PD.

American Strain of Zika Virus Causes More Severe Microcephaly Than an Old Asian Strain in Neonatal Mice

Zika virus (ZIKV) has evolved from an overlooked mosquito-borne flavivirus into a global health threat due to its astonishing causal link to microcephaly and other disorders. ZIKV has been shown to infect neuronal progenitor cells of the fetal mouse brain, which is comparable to the first-trimester human fetal brain, and result in microcephaly. However, whether there are different effects between the contemporary ZIKV strain and its ancestral strain in the neonatal mouse brain, which is comparable with the second-trimester human fetal brain, is unclear. Here we adopted a mouse model which enables us to study the postnatal effect of ZIKV infection. We show that even 100 pfu of ZIKV can replicate and infect neurons and oligodendrocytes in most parts of the brain. Compared with the ancestral strain from Cambodia (CAM/2010), infection of the ZIKV strain from Venezuela (VEN/2016) leads to much more severe microcephaly, accompanied by more neuronal cell death, abolishment of oligodendrocyte development, and a more dramatic immune response. The serious brain damage caused by VEN/2016 infection would be helpful to elucidate why the American strain resulted in severe neurovirulence in infants and will provide clinical guidance for the diagnosis and treatment of infection by different ZIKV strains.

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The infection of an American strain of ZIKV leads to more severe microcephaly than the ancestral Asian strain.

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American strain infects more cells, and induces more dramatic immune response and cell death than ancestral Asian strain.

World attention has been drawn to a global Zika virus (ZIKV) outbreak due to its unexpected causal link to congenital brain abnormalities, especially microcephaly. Infection of pregnant women with the American Zika strain, but not the ancestral Asian strain, can result in microcephaly in infants. However, the phenotypic difference between the contemporary American strain and ancestral Asian strain of ZIKV is still unclear. We employed the ZIKV infection model of a neonatal mouse brain to compare the difference between these two strains. We find that infection by the American strain leads to more severe microcephaly than the ancestral Asian strain.

Joint Toxicity of Different Heavy Metal Mixtures after a Short-Term Oral Repeated-Administration in Rats

The systemic toxicity of different combinations of heavy metal mixtures (HMMs) was studied according to equivalent proportions of the eight most common detectable heavy metals found in fish consumption in the Ningbo area of China. The ion mass proportions of Zn, Cu, Mn, Cr, Ni, Cd, Pb, and Hg were 1070.0, 312.6, 173.1, 82.6, 30.0, 13.3, 6.6, and 1.0, respectively. In this study, 10 experimental groups were set as follows: M8 (Pb + Cd + Hg + Ni + Cu + Zn + Mn + Cr); M5 (Pb + Cd + Hg + Ni + Cr); M4A (Pb + Cd + Hg + Ni); M4B (Cu + Zn + Mn + Cr); M3 (Cu + Zn + Mn); Cr; Cu; Zn; Mn; and control. Sprague Dawley (SD) rats were orally treated with a single dose of each group every three days (10 times in total) for 34 days. After Morris water maze test, blood and tissue samples were collected to obtain biochemical, histopathological and western blot analysis. Results show abnormalities could be observed in different treatment groups, the M4B combination had the most significant change compared to all other groups. In conclusion, combination HMMs may have adverse effects on the hematologic, hepatic, renal and neurobehavioral function, and may also disturb electrolyte and lipid balance. Why M4B combination generated much higher toxic effects than any other combination mixtures or individual heavy metal needs to be further evaluated.

Neuronal Migration and AUTS2 Syndrome

Neuronal migration is one of the pivotal steps to form a functional brain, and disorganization of this process is believed to underlie the pathology of psychiatric disorders including schizophrenia, autism spectrum disorders (ASD) and epilepsy. However, it is not clear how abnormal neuronal migration causes mental dysfunction. Recently, a key gene for various psychiatric diseases, the Autism susceptibility candidate 2 (AUTS2), has been shown to regulate neuronal migration, which gives new insight into understanding this question. Interestingly, the AUTS2 protein has dual functions: Cytoplasmic AUTS2 regulates actin cytoskeleton to control neuronal migration and neurite extension, while nuclear AUTS2 controls transcription of various genes as a component of the polycomb complex 1 (PRC1). In this review, we discuss AUTS2 from the viewpoint of human genetics, molecular function, brain development, and behavior in animal models, focusing on its role in neuronal migration.

Disruptions in asymmetric centrosome inheritance and WDR62-Aurora kinase B interactions in primary microcephaly

Recessive mutations in WD repeat domain 62 (WDR62) cause microcephaly and a wide spectrum of severe brain malformations. Disruption of the mouse ortholog results in microcephaly underlain by reduced proliferation of neocortical progenitors during late neurogenesis, abnormalities in asymmetric centrosome inheritance leading to neuronal migration delays, and altered neuronal differentiation. Spindle pole localization of WDR62 and mitotic progression are defective in patient-derived fibroblasts, which, similar to mouse neocortical progenitors, transiently arrest at prometaphase. Expression of WDR62 is closely correlated with components of the chromosome passenger complex (CPC), a key regulator of mitosis. Wild type WDR62, but not disease-associated mutant forms, interacts with the CPC core enzyme Aurora kinase B and staining of CPC components at centromeres is altered in patient-derived fibroblasts. Our findings demonstrate critical and diverse functions of WDR62 in neocortical development and provide insight into the mechanisms by which its disruption leads to a plethora of structural abnormalities.