Although diabetic encephalopathy (DE) is a major late complication of diabetes, the pathophysiology of postural instability in DE remains poorly understood. Prior studies have suggested that neuronal apoptosis is closely associated with cognitive function, but the mechanism remains to be elucidated. Green tea, which is a non-fermented tea, contains a number of tea polyphenols, alkaloids, amino acids, polysaccharides and other components. Some studies have found that drinking green tea can reduce the incidence of neurodegenerative diseases and improve cognitive dysfunction. We previously found that myosin light chain kinase (MLCK) regulates apoptosis in high glucose-induced hippocampal neurons. In neurodegenerative diseases, including Alzheimer's disease and Parkinson's disease, activation of the JNK signaling pathway promotes neuronal apoptosis. However, the relationship between JNK and MLCK remains to be elucidated. Green tea serum was obtained using seropharmacological methods and applied to hippocampal neurons. In addition, a type 1 diabetes rat model was established and green tea extract was administered, and the Morris water maze test, Cell Counting Kit-8 assays, flow cytometry, western blotting and terminal deoxynucleotidyl transferase-mediated dUTP nick end-labelling assays were used to examine the effects of green tea on hippocampal neuronal apoptosis in diabetic rats. The results demonstrated that green tea can protect against hippocampal neuronal apoptosis by inhibiting the JNK/MLCK pathway and ultimately improves cognitive function in diabetic rats. The present study provided novel insights into the neuroprotective effects of green tea.

• JNK/myosin light chain kinase signaling pathway
• cognitive function
• diabetic encephalopathy
• green tea
• hippocampal neuron apoptosis

• Behavior
• Cognition
• Signal transduction
• Synapse
• Vitamin B12

• Animals
• Behavior, Animal/drug effects
• Brain/physiopathology
• Cognition/drug effects
• Disease Models, Animal
• Glucocorticoids/pharmacology
• Hippocampus/drug effects
• Hippocampus/physiopathology
• Hydrocortisone/administration & dosage
• Hydrocortisone/pharmacology
• Male
• Memory
• Mice, Knockout
• Neuronal Plasticity/drug effects
• Neuronal Plasticity/physiology
• Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha/metabolism
• Receptors, Cell Surface/deficiency
• Receptors, Cell Surface/metabolism
• Receptors, Glucocorticoid/metabolism
• Signal Transduction/drug effects
• Stress, Physiological/drug effects
• Vitamin B 12 Deficiency/physiopathology
• Mice

• DEHP
• dendritic spine
• hippocampus
• synapse
• synaptic plasticity

• Animals
• Dendritic Spines
• Diethylhexyl Phthalate/toxicity
• Female
• Hippocampus
• Humans
• Male
• Maternal Exposure
• Neuronal Plasticity
• Phthalic Acids
• Pregnancy
• Prenatal Exposure Delayed Effects
• Rats
• Rats, Wistar

Cell-cell interaction as one of the niche signals plays an important role in the balance of stem cell quiescence and proliferation or differentiation. In order to address the effect and the possible mechanisms of cell-cell connection on neural stem/progenitor cells (NSCs/NPCs) proliferation and differentiation, upon passaging, NSCs/NPCs were either dissociated into single cell as usual (named Group I) or mechanically triturated into a mixture of single cell and small cell clusters containing direct cell-cell connections (named Group II). Then the biological behaviors including proliferation and differentiation of NSCs/NPCs were observed. Moreover, the expression of gap junction channel, neurotrophic factors and the phosphorylation status of MAPK signals were compared to investigate the possible mechanisms. Our results showed that, in comparison to the counterparts in Group I, NSCs/NPCs in Group II survived well with preferable neuronal differentiation. In coincidence with this, the expression of connexin 45 (Cx45), as well as brain derived neurotrophic factor (BDNF) and neurotrophin 3 (NT-3) in Group II were significantly higher than those in Group I. Phosphorylation of ERK1/2 and JNK2 were significantly upregulated in Group II too, while no change was found about p38. Furthermore, the differences of NSCs/NPCs biological behaviors between Group I and II completely disappeared when ERK and JNK phosphorylation were inhibited. These results indicated that cell-cell connection in Group II enhanced NSCs/NPCs survival, proliferation and neuronal differentiation through upregulating the expression of gap junction and neurotrophic factors. MAPK signals- ERK and JNK might contribute to the enhancement. Efforts for maintaining the direct cell-cell connection are worth making to provide more favorable niches for NSCs/NPCs survival, proliferation and neuronal differentiation.

• MAPK
• NSCs/NPCs
• cell-cell connection
• neuronal differentiation
• proliferation

The SNARE-mediated vesicular transport pathway plays major roles in synaptic remodeling associated with formation of long-term memories, but the mechanisms that regulate this pathway during memory acquisition are not fully understood. Here we identify miRNAs that are up-regulated in the rodent hippocampus upon contextual fear-conditioning and identify the vesicular transport and synaptogenesis pathways as the major targets of the fear-induced miRNAs. We demonstrate that miR-153, a member of this group, inhibits the expression of key components of the vesicular transport machinery, and down-regulates Glutamate receptor A1 trafficking and neurotransmitter release. MiR-153 expression is specifically induced during LTP induction in hippocampal slices and its knockdown in the hippocampus of adult mice results in enhanced fear memory. Our results suggest that miR-153, and possibly other fear-induced miRNAs, act as components of a negative feedback loop that blocks neuronal hyperactivity at least partly through the inhibition of the vesicular transport pathway.

DOI:http://dx.doi.org/10.7554/eLife.22467.001

• cell biology
• hippocampus
• learning
• memory
• miRNA
• mouse
• negative feed back loop
• rat
• synaptic plasticity

The micronutrients folate and vitamin B12 are essential for the proper development of the central nervous system, and their deficiency during pregnancy has been associated with a wide range of disorders. They act as methyl donors in the one-carbon metabolism which critically influences epigenetic mechanisms. In order to depict further underlying mechanisms, we investigated the role of let-7 and miR-34, two microRNAs regulated by methylation, on a rat model of maternal deficiency. In several countries, public health policies recommend periconceptional supplementation with folic acid. However, the question about the duration and periodicity of supplementation remains. We therefore tested maternal supply (3 mg/kg/day) during the last third of gestation from embryonic days (E) 13 to 20. Methyl donor deficiency-related developmental disorders at E20, including cerebellar and interhemispheric suture defects and atrophy of selective cerebral layers, were associated with increased brain expression (by 2.5-fold) of let-7a and miR-34a, with subsequent downregulation of their regulatory targets such as Trim71 and Notch signaling partners, respectively. These processes could be reversed by siRNA strategy in differentiating neuroprogenitors lacking folate, with improvement of their morphological characteristics. While folic acid supplementation helped restoring the levels of let-7a and miR-34a and their downstream targets, it led to a reduction of structural and functional defects taking place during the perinatal period. Our data outline the potential role of let-7 and miR-34 and their related signaling pathways in the developmental defects following gestational methyl donor deficiency and support the likely usefulness of late folate supplementation in at risk women.

• Belated folate supplementation
• Brain development
• Epigenetics
• Folate
• Vitamin B12
• microRNAs

Functional synaptogenesis and network emergence are signature endpoints of neurogenesis. These behaviors provide higher-order confirmation that biochemical and cellular processes necessary for neurotransmitter release, post-synaptic detection and network propagation of neuronal activity have been properly expressed and coordinated among cells. The development of synaptic neurotransmission can therefore be considered a defining property of neurons. Although dissociated primary neuron cultures readily form functioning synapses and network behaviors in vitro, continuously cultured neurogenic cell lines have historically failed to meet these criteria. Therefore, in vitro-derived neuron models that develop synaptic transmission are critically needed for a wide array of studies, including molecular neuroscience, developmental neurogenesis, disease research and neurotoxicology. Over the last decade, neurons derived from various stem cell lines have shown varying ability to develop into functionally mature neurons. In this review, we will discuss the neurogenic potential of various stem cells populations, addressing strengths and weaknesses of each, with particular attention to the emergence of functional behaviors. We will propose methods to functionally characterize new stem cell-derived neuron (SCN) platforms to improve their reliability as physiological relevant models. Finally, we will review how synaptically active SCNs can be applied to accelerate research in a variety of areas. Ultimately, emphasizing the critical importance of synaptic activity and network responses as a marker of neuronal maturation is anticipated to result in in vitro findings that better translate to efficacious clinical treatments.

• Synapses
• Neurotransmission
• In vitro techniques
• Induced pluripotent stem cells
• Neuronal networks
• Neurogenesis
• Neural stem cells
• Embryonic stem cells
• Induced neurons

The methyl donors folate (vitamin B9) and vitamin B12 are centrepieces of the one-carbon metabolism that has a key role in transmethylation reactions, and thus in epigenetic and epigenomic regulations. Low dietary intakes of folate and vitamin B12 are frequent, especially in pregnant women and in the elderly, and deficiency constitutes a risk factor for various diseases, including neurological and developmental disorders. In this respect, both vitamins are essential for normal brain development, and have a role in neuroplasticity and in the maintenance of neuronal integrity. The consequences of a methyl donor deficiency (MDD) were studied both in vivo in rats exposed in utero, and in vitro in hippocampal progenitors (H19-7 cell line). Deficiency was associated with growth retardation at embryonic day 20 (E20) and postnatally with long-term brain defects in selective areas. mRNA and protein levels of the transcription factor Stat3 were found to be decreased in the brains of deprived fetuses and in differentiating progenitors (62 and 48% for total Stat3 protein, respectively), along with a strong reduction in its phosphorylation at both Tyr⁷⁰⁵ and Ser⁷²⁷ residues. Vitamin shortage also affected upstream kinases of Stat3 signaling pathway (phospho-Erk1/2, phospho-Src, phospho-JNK, and phospho-p38) as well as downstream target gene products (Bcl-2 and Bcl-xL), thus promoting apoptosis. Conversely, the expression of the Stat3 regulator miR-124 was upregulated in deficiency conditions (≥65%), and its silencing by using siRNA partly restored Stat3 signaling in hippocampal neurons by increasing specifically the phosphorylation of Erk1/2 and Src kinases. Furthermore, miR-124 siRNA improved the phenotype of deprived cells, with enhanced neurite outgrowth. Taken together, our data suggest that downregulation of Stat3 signaling by miR-124 would be a key factor in the deleterious effects of MDD on brain development.

• Animals
• Dentate Gyrus/cytology
• Dentate Gyrus/physiology
• Hippocampus/cytology
• Hippocampus/physiology
• Learning/physiology
• Male
• Neurogenesis
• Neurons/cytology
• Octodon
• Spatial Behavior/physiology
• Synapses/metabolism
• Tool Use Behavior/physiology

Neural stem cell transplantation is a promising tool for the restoration of the enteric nervous system in a variety of motility disorders. However, limited cell viability after transplantation has restricted its regenerative capacity. The aim of this study was to evaluate the effect of transplantation of neuroepithelial stem cell (NESC) overexpressing anti-apoptotic gene Bcl-2 on the survival, differentiation and function of grafted cells in rat aganglionic colon.

NESCs were isolated from neural tube of embryonic rat (embryonic day 11.5) and manipulated to overexpress the Bcl-2 gene. After transplantation into the benzalkonium chloride-induced rat aganglionic colon, grafted cells were visualized in colonic sections. Apoptosis and differentiation of the implanted cells were assessed 1, 4 and 8 weeks post transplantation, respectively. Eight weeks post transplantation, neuronal function of the colon was assessed by measuring the response of muscle strips to electrical field stimulation.

Transplantation with Bcl-2-NESCs reduced apoptosis within the transplant at 1 week compared with the vector-NESC grafted group. Our findings also indicated that overexpression of Bcl-2 in the transplanted NESCs enhanced differentiation into PGP9.5-positive and neuronal nitric oxide synthase-positive neurons at 8-week assessment. Moreover, electrical field stimulation-induced relaxation of colonic strips was also significantly increased in the Bcl-2-NESC grafted group.

Transplantation of NESCs genetically modified to overexpress Bcl-2 may have value for enhancing survival and neurogenesis of grafted cells in the adult gut environment and for improving the efficacy of stem cell therapy following a broad range of gastrointestinal motility disorders.