Folic acid deficiency inhibits neural rosette formation and neuronal differentiation from rhesus monkey embryonic stem cells

Methyl donor micronutrients, hypothalamic development and programming for metabolic disease

Nutriture in utero is essential for fetal brain development through the regulation of neural stem cell proliferation, differentiation, and apoptosis, and has a long-lasting impact on risk of disease in offspring. This review examines the role of maternal methyl donor micronutrients in neuronal development and programming of physiological functions of the hypothalamus, with a focus on later-life metabolic outcomes. Although evidence is mainly derived from preclinical studies, recent research shows that methyl donor micronutrients (e.g., folic acid and choline) are critical for neuronal development of energy homeostatic pathways and the programming of characteristics of the metabolic syndrome in mothers and their children. Both folic acid and choline are active in one-carbon metabolism with their impact on epigenetic modification of gene expression. We conclude that an imbalance of folic acid and choline intake during gestation disrupts DNA methylation patterns affecting mechanisms of hypothalamic development, and thus elevates metabolic disease risk. Further investigation, including studies to determine translatability to humans, is required.

Hesperidin ameliorates impairment in hippocampal neural stem cells related to apoptosis induced by methotrexate in adult rats

Neurogenesis is a process of generating neural stem cells (NSCs) as functional neurons can be decreased after chemotherapy treatments. Methotrexate (MTX) is a folate antagonist that is used for cancer treatment but has negative effects, including oxidative stress, neuronal apoptosis and cognitive impairments. Hesperidin (Hsd), a flavonoid found in citrus fruits, has antioxidant and neuroprotection properties. This study investigated whether Hsd could attenuate impairments of hippocampal neural stem cells related to apoptosis induced by MTX. Spraque-Dawley rats (n = 24) were divided into 4 groups: (1) Vehicle group received propylene glycol (21 days) and 0.9% normal saline (day 8 and 15), (2) Hsd group received 100 mg/kg (21 days), (3) MTX group received 75 mg/kg (days 8 and 15) and (4) MTX+Hsd group received MTX, 75 mg/kg (day 8 and 15) and Hsd 100 mg/kg (21 days). Our results showed that MTX decreased hippocampal neural stem cells including SRY (sex determining region Y)-box 2 (SOX2) and nestin. MTX diminished vascular related (VR) Ki-67 positive cells in the hippocampus but not non-vascular related (NVR) Ki-67. Additionally, MTX reduced SOX2, nestin, postsynaptic density protein 95 (PSD-95) and B-cell lymphoma-2 family of proteins (Bcl-2), whereas Bax and caspase-3 were enhanced in the hippocampal tissues. Interestingly, co-treatment with Hsd and MTX revealed upregulation of SOX2, nestin and VR Ki-67 positive cells as well as elevated SOX2, nestin, PSD-95 and Bcl-2 proteins. Moreover, receiving both Hsd and MTX significantly suppressed increased Bax and caspase-3. These results confirm that Hsd can ameliorate MTX-induced impairments of hippocampal NSC proliferation and neuronal apoptosis.

Collective behavior and self-organization in neural rosette morphogenesis

Neural rosettes develop from the self-organization of differentiating human pluripotent stem cells. This process mimics the emergence of the embryonic central nervous system primordium, i.e., the neural tube, whose formation is under close investigation as errors during such process result in severe diseases like spina bifida and anencephaly. While neural tube formation is recognized as an example of self-organization, we still do not understand the fundamental mechanisms guiding the process. Here, we discuss the different theoretical frameworks that have been proposed to explain self-organization in morphogenesis. We show that an explanation based exclusively on stem cell differentiation cannot describe the emergence of spatial organization, and an explanation based on patterning models cannot explain how different groups of cells can collectively migrate and produce the mechanical transformations required to generate the neural tube. We conclude that neural rosette development is a relevant experimental 2D in-vitro model of morphogenesis because it is a multi-scale self-organization process that involves both cell differentiation and tissue development. Ultimately, to understand rosette formation, we first need to fully understand the complex interplay between growth, migration, cytoarchitecture organization, and cell type evolution.

Folic Acid Attenuates Glial Activation in Neonatal Mice and Improves Adult Mood Disorders Through Epigenetic Regulation

Growing evidence indicates that postnatal immune activation (PIA) can adversely increase the lifetime risk for several neuropsychiatric disorders, including anxiety and depression, which involve the activation of glial cells and early neural developmental events. Several glia-targeted agents are required to protect neonates. Folic acid (FA), a clinical medication used during pregnancy, has been reported to have neuroprotective properties. However, the effects and mechanisms of FA in PIA-induced neonatal encephalitis and mood disorders remain unclear. Here, we investigated the roles of FA in a mouse model of PIA, and found that FA treatment improved depressive- and anxiety-like behaviors in adults, accompanied by a decrease in the number of activated microglia and astrocytes, as well as a reduction in the inflammatory response in the cortex and hippocampus of neonatal mice. Furthermore, we offer new evidence describing the functional differences in FA between microglia and astrocytes. Our data show that epigenetic regulation plays an essential role in FA-treated glial cells following PIA stimulation. In astrocytes, FA promoted the expression of IL-10 by decreasing the level of EZH2-mediated H3K27me3 at its promoter, whereas FA promoted the expression of IL-13 by reducing the promoter binding of H3K9me3 mediated by KDM4A in microglia. Importantly, FA specifically regulated the expression level of BDNF in astrocytes through H3K27me3. Overall, our data supported that FA may be an effective treatment for reducing mood disorders induced by PIA, and we also demonstrated significant functional differences in FA between the two cell types following PIA stimulation.

Low folate induces abnormal neuronal maturation and DNA hypomethylation of neuronal differentiation-related genes in cultured mouse neural stem and progenitor cells

Folate deficiency in a fetus is well known to cause neurodevelopment defects and development disorders. A low level of folate is also thought to be a risk for depression in adults. We have previously shown that post-weaning low folate induces neuronal immaturity in the dentate gyrus in mice, which suggests that low folate causes neuropsychological disorders via inhibition of neuronal maturation. In this study, we examined the effects of low folate on expression and epigenetic modification of genes involved in neuronal differentiation and maturation in primary mouse neural stem/progenitor cells (NSPCs) in vitro. An increase in Nestin (NSPC marker)-positive cells was observed in cells differentiated in a low folate medium for 3 days. An increase in βIII-tubulin (Tuj1: immature neuron marker)-positive cells and a decrease in microtubule-associated protein 2 (MAP2: mature neuron marker)-positive cells were observed in cells differentiated in a low folate medium for 7 days. In these cells, mRNA levels for genes involved in neuronal differentiation and maturation were altered. Hypomethylation of DNA, but not of histone proteins, was also observed at some promoters of these neuronal genes. The level of S-adenosylmethionine (SAM), a methyl donor, was decreased in these cells. The abnormalities in neural maturation and changes in gene expression in culture under low folate conditions were partially normalized by addition of SAM (5 μM). Based on these results, decreased SAM may induce DNA hypomethylation at genes involved in neuronal differentiation and maturation under low folate conditions, and this hypomethylation may be associated with low folate-induced neuronal immaturity.

First trimester mechanisms of gestational sac placental and foetal teratogenicity: a framework for birth cohort studies

BACKGROUND

The function of the gestational sac (GS) and the placenta in the closely related processes of embryogenesis and teratogenicity in the first trimester has been minimally described. The prevailing assumption is that direct teratogenic effects are mediated by the critical extraembryonic organ, the placenta, which either blocks or transfers exposures to the foetus. Placental transfer is a dominant mechanism, but there are other paradigms by which the placenta can mediate teratogenic effects. Knowledge of these paradigms and first trimester human developmental biology can be useful to the epidemiologist in the conduct of biomarker-based studies of both maternal and child health.

OBJECTIVE AND RATIONALE

Our aim is to provide a causal framework for modelling the teratogenic effects of first trimester exposures on child health outcomes mediated by the GS and placenta using biomarker data collected in the first trimester. We initially present first trimester human developmental biology for the sake of informing and strengthening epidemiologic approaches. We then propose analytic approaches of modelling placental mechanisms by way of causal diagrams using classical non-embryolethal teratogens (diethylstilboestrol [DES], folic acid deficiency and cytomegalovirus [CMV]) as illustrative examples. We extend this framework to two chronic exposures of particular current interest, phthalates and maternal adiposity.

SEARCH METHODS

Information on teratogens was identified by a non-systematic, narrative review. For each teratogen, we included papers that answered the five following questions: (i) why were these exposures declared teratogens? (ii) is there a consensus on biologic mechanism? (iii) is there reported evidence of a placental mechanism? (iv) can we construct a theoretical model of a placental mechanism? and (v) can this knowledge inform future work on measurement and modelling of placental-foetal teratogenesis? We prioritized literature specific to human development, the organogenesis window in the first trimester and non-embryolethal mechanisms.

OUTCOMES

As a result of our review of the literature on five exposures considered harmful in the first trimester, we developed four analytic strategies to address first trimester placental mechanisms in birth cohort studies: placental transfer and direct effects on the foetus (DES and maternal adiposity), indirect effects through targeted placental molecular pathways (DES and phthalates), pre-placental effects through disruptions in embryonic and extraembryonic tissue layer differentiation (folic acid deficiency), and multi-step mechanisms that involve maternal, placental and foetal immune function and inflammation (DES and CMV).

WIDER IMPLICATIONS

The significance of this review is to offer a causal approach to classify the large number of potentially harmful exposures in pregnancy when the exposure occurs in the first trimester. Our review will facilitate future research by advancing knowledge of the first trimester mechanisms necessary for researchers to effectively associate environmental exposures with child health outcomes.

From Embryo to Adult: One Carbon Metabolism in Stem Cells

Stem cells are undifferentiated cells with self-renewal property and varying differentiation potential that allow the regeneration of tissue cells of an organism throughout adult life beginning from embryonic development. Through the asymmetric cell divisions, each stem cell replicates itself and produces an offspring identical with the mother cell, and a daughter cell that possesses the characteristics of a progenitor cell and commits to a specific lineage to differentiate into tissue cells to maintain homeostasis. To maintain a pool of stem cells to ensure tissue regeneration and homeostasis, it is important to regulate the metabolic functioning of stem cells, progenitor cells and adult tissue stem cells that will meet their internal and external needs. Upon fertilization, the zygote transforms metabolic reprogramming while implantation, embryonic development, organogenesis processes and after birth through adult life. Metabolism in stem cells is a concept that is relatively new to be enlightened. There are no adequate and comprehensive in vitro studies on the comparative analysis of the effects of one-carbon (1-C) metabolism on fetal and adult stem cells compared to embryonic and cancer stem cells' studies that have been reported recently. Since 1-C metabolism is linking parental environmental/ dietary factors and fetal development, investigating the epigenetic, genetic, metabolic and developmental effects on adult period is necessary. Several mutations and abnormalities in 1-C metabolism have been noted in disease changing from diabetes, cancer, pregnancy-related outcomes such as pre-eclampsia, spontaneous abortion, placental abruption, premature delivery, and cardiovascular diseases. In this review, the effects of 1-C metabolism, mainly the methionine and folate metabolism, in stem cells that exist in different developmental stages will be discussed.

Culture Conditions Affect Chemical-Induced Developmental Toxicity In Vitro: The Case of Folic Acid, Methionine and Methotrexate in the Neural Embryonic Stem Cell Test

In vitro tests are increasingly applied in chemical hazard assessment. Basic culture conditions may affect the outcome of in vitro tests and should be optimised to reduce false predictions. The neural embryonic stem cell test (ESTn) can predict early neurodevelopmental effects of chemicals, as it mimics the differentiation of stem cells towards the neuroectodermal lineage. Normal early neural differentiation depends crucially on folic acid (FA) and methionine (MET), both elements of the one-carbon (1C) cycle. The aim of this study was to assess the concentration-dependent influence of FA and MET on neural differentiation in the ESTn, and its consequences for assay sensitivity to methotrexate (MTX), a compound that interferes with the 1C cycle. Neural differentiation was inhibited below 0.007 mM and above 0.22 mM FA, while both stem cell viability (< 0.097 mM, > 1.52 mM) and neural differentiation (< 0.181 mM, > 1.35 mM) were affected when changing MET concentrations. A 10-day exposure to 13 nM MTX inhibited neural differentiation, especially in FA- and MET-deficient conditions. However, a 24-hour exposure to 39 nM MTX decreased neural cell and neural crest cell differentiation markers only when the concentration of FA in the medium was three times the standard concentration, which was expected to have a protective effect against MTX. These results show the importance of nutrient concentrations, exposure scenarios and timing of read-outs for cell differentiation and compound sensitivity in the ESTn. Caution should be taken when interpreting results from a single in vitro test, especially when extrapolating to effects on complex morphogenetic processes, like neural tube development.

Maternal Folic Acid Supplementation During Pregnancy Promotes Neurogenesis and Synaptogenesis in Neonatal Rat Offspring

Maternal folic acid supplementation during pregnancy is associated with improved cognitive performances in offspring. However, the effect of supplementation on offspring's neurogenesis and synaptogenesis is unknown, and whether supplementation should be continued throughout pregnancy is controversial. In present study, 3 groups of female rats were fed a folate-normal diet, folate-deficient diet, or folate-supplemented diet from 1 week before mating until the end of pregnancy. A fourth group fed folate-normal diet from 1 week before mating until mating, then fed folate-supplemented diet for 10 consecutive days, then fed folate-normal diet until the end of pregnancy. Offspring were sacrificed on postnatal day 0 for measurement of neurogenesis and synaptogenesis by immunofluorescence and western blot. Additionally neural stem cells (NSCs) were cultured from offspring's hippocampus for immunocytochemical measurement of their rates of proliferation and neuronal differentiation. The results demonstrated that maternal folic acid supplementation stimulated hippocampal neurogenesis by increasing proliferation and neuronal differentiation of NSCs, and also enhanced synaptogenesis in cerebral cortex of neonatal offspring. Hippocampal neurogenesis was stimulated more when supplementation was continued throughout pregnancy instead of being limited to the periconceptional period. In conclusion, maternal folic acid supplementation, especially if continued throughout pregnancy, improves neurogenesis and synaptogenesis in neonatal offspring.

Effects of folic acid withdrawal on transcriptomic profiles in murine triple-negative breast cancer cell lines

We have previously shown that withdrawal of folic acid led to metabolic reprogramming and a less aggressive phenotype in a mouse cell model of triple-negative breast cancer (TNBC). Herein, we evaluate the effects of folic acid withdrawal on transcriptomic profiles in these cells. Murine cell lines were originally derived from a pool of spontaneous mammary tumors grown in MMTV-Wnt1 transgenic mice. Based on their differential molecular characteristics and metastatic potential, these cell lines were previously characterized as non-metastatic epithelial (E-Wnt), non-metastatic mesenchymal (M-Wnt) and metastatic mesenchymal (metM-Wnt^liver) cells. Using custom two-color 180K Agilent microarrays, we have determined gene expression profiles for three biological replicates of each subtype kept on standard medium (2.2 μM folic acid) or folic acid-free medium for 72 h. The analyses revealed that more genes were differentially expressed upon folic acid withdrawal in M-Wnt cells (1884 genes; Benjamini-Hochberg-adjusted P-value <0.05) compared to E-Wnt and metM-Wnt^liver cells (108 and 222 genes, respectively). Pathway analysis has identified that type I interferon signaling was strongly affected by folic acid withdrawal, with interferon-responsive genes consistently being upregulated upon folic acid withdrawal in M-Wnt cells. Of note, repressed interferon signaling has been established as one of the characteristics of aggressive human TNBC, and hence reactivation of this pathway may be a promising therapeutic approach. Overall, while our study indicates that the response to folic acid withdrawal varies by molecular subtype and cellular phenotype, it also underscores the necessity to further investigate one-carbon metabolism as a potential therapeutic means in the treatment of advanced TNBC.

Up-regulation of RNA Binding Proteins Contributes to Folate Deficiency-Induced Neural Crest Cells Dysfunction

Folate deficiency has long been associated with the abnormal development of the neural crest cells (NCCs) and neural tube defects (NTDs). RNA binding proteins (RBPs) also play important roles in the normal neural crest development and neural tube formation. Nevertheless, the causative mechanism by which folate status influences human NCCs development and the RBPs functions remains unknown. In this study, we differentiated H9 human embryonic stem cells into neural crest cells (H9-NCCs) and then constructed three folic acid (FA) deficiency (FAD) H9-NCCs models in vitro. Decreased viability, impaired migration and promoted apoptosis of H9-NCCs were observed in three FAD H9-NCCs models. In addition, we showed that three RBPs, namely, hnRNPC, LARP6 and RCAN2, were up-regulated both in the FAD H9-NCC models in vitro and in the FAD mouse model in vivo. Knocking down of these three RBPs increased the H9-NCC viability and RCAN2 knockdown further promoted H9-NCC migration under FAD conditions. In normal culture condition, overexpression of RCAN2 and HnRNPC did not affect viabilities and migration of H9-NCCs while overexpression of LARP6 reduced the H9-NCC viability. Our findings demonstrate important regulatory effects of RBPs underlying FAD-induced impaired function of NCCs.

Folate deficiency induced H2A ubiquitination to lead to downregulated expression of genes involved in neural tube defects

BACKGROUND

Neural tube defects (NTDs) are common congenital malformations resulting in failure of the neural tube closure during early embryonic development. Although it is known that maternal folate deficiency increases the risk of NTDs, the mechanism remains elusive.

RESULTS

Herein, we report that histone H2A monoubiquitination (H2AK119ub1) plays a role in neural tube closure. We found that the folate antagonist methotrexate induced H2AK119ub1 in mouse embryonic stem cells. We demonstrated that an increase in H2AK119ub1 downregulated expression of the neural tube closure-related genes Cdx2, Nes, Pax6, and Gata4 in mouse embryonic stem cells under folate deficiency conditions. We also determined that the E3 ligase Mdm2 was responsible for the methotrexate-induced increase in H2AK119ub1 and downregulation of neural tube closure-related genes. Surprisingly, we found that Mdm2 is required for MTX-induced H2A ubiquitination and is recruited to the sites of DSB, which is dependent on DNA damage signaling kinase ATM. Furthermore, folic acid supplementation restored H2AK119ub1 binding to neural tube closure-related genes. Downregulation of these genes was also observed in both brain tissue of mouse and human NTD cases, and high levels of H2AK119ub1 were found in the corresponding NTDs samples with their maternal serum folate under low levels. Pearson correlation analysis showed a significant negative correlation between expression of the neural precursor genes and H2AK119ub1.

CONCLUSION

Our results indicate that folate deficiency contributes to the onset of NTDs by altering H2AK119ub1 and subsequently affecting expression of neural tube closure-related genes. This may be a potential risk factor for NTDs in response to folate deficiency.

Metabolic-Epigenetic Axis in Pluripotent State Transitions

Cell state transition (CST) occurs during embryo development and in adult life in response to different stimuli and is associated with extensive epigenetic remodeling. Beyond growth factors and signaling pathways, increasing evidence point to a crucial role of metabolic signals in this process. Indeed, since several epigenetic enzymes are sensitive to availability of specific metabolites, fluctuations in their levels may induce the epigenetic changes associated with CST. Here we analyze how fluctuations in metabolites availability influence DNA/chromatin modifications associated with pluripotent stem cell (PSC) transitions. We discuss current studies and focus on the effects of metabolites in the context of naïve to primed transition, PSC differentiation and reprogramming of somatic cells to induced pluripotent stem cells (iPSCs), analyzing their mechanism of action and the causal correlation between metabolites availability and epigenetic alteration.

An appraisal of folates as key factors in cognition and ageing-related diseases

Folic acid (FA) is often consumed as a food supplement and can be found in fortified staple foods in various western countries. Even though FA supplementation during pregnancy is known to prevent severe congenital anomalies in the developing child (e.g., neural tube defects), much less is known about its influence on cognition and neurological functioning. In this review, we address the advances in this field and situate how folate intake during pregnancy, postnatal life, adulthood and in the elderly affects cognition. In addition, an association between folate status and ageing, dementia and other neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis is discussed. While its role in the incidence and severity of these diseases is becoming apparent, the underlying action of folates and related metabolites remains elusive. Finally, the potential of FA as a nutraceutical has been proposed, although the efficacy will highly depend on the interplay with other micronutrients, the disease stage and the duration of supplementation. Hence, the lack of consistent data urges for more animal studies and (pre)clinical trials in humans to ascertain a potential beneficial role for folates in the treatment or amelioration of cognitive decline and ageing-related disorders.

Interaction of p53 and ASPPs regulates rhesus monkey embryonic stem cells conversion to neural fate concomitant with apoptosis

The tumor suppressor p53 is a key regulator of cell apoptosis and cell cycle arrest. Recent studies show that the delicate balance of p53 expression is important for neural tube defects, neuronal degeneration, embryonic lethality, as well as differentiation and dedifferentiation. Moreover, p53 showed different regulatory patterns between rodent and primate embryonic stem cells (ESCs). However, the role of p53 and apoptosis stimulating protein of p53 (ASPP) during neural differentiation (ND) from primate ESCs is still unknown. In this study, using an FGF-2 and/or HGF selectively containing ND culture systems for rhesus monkey ESCs (rESCs), the changes of p53 and ASPPs, and p53 targets, i.e. BAX and p21, were analyzed. Our results showed that the expression patterns of ASPP1/ASPP2 and iASPP were opposite in rESCs but similar in differentiated cells, and the expression of p53 was approximately consistent with BAX, but not p21. These findings indicate that the strong expression of iASPP in ESCs and weak expression of ASPP1/ASPP2 maintain the stability of stemness; and in ND niche, unimpaired iASPP may decrease its inhibition of ASPP1/ASPP2 expression, the interaction of p53 and ASPPs causing rESCs to convert towards a neural fate concomitant with apoptosis, but not to cell cycle arrest.

Folic Acid Exposure Rescues Spina Bifida Aperta Phenotypes in Human Induced Pluripotent Stem Cell Model

Neural tube defects (NTDs) are severe congenital abnormalities, caused by failed closure of neural tube during early embryonic development. Periconceptional folic acid (FA) supplementation greatly reduces the risk of NTDs. However, the molecular mechanisms behind NTDs and the preventive role of FA remain unclear. Here, we use human induced pluripotent stem cells (iPSCs) derived from fetuses with spina bifida aperta (SBA) to study the pathophysiology of NTDs and explore the effects of FA exposure. We report that FA exposure in SBA model is necessary for the proper formation and maturation of neural tube structures and robust differentiation of mesodermal derivatives. Additionally, we show that the folate antagonist methotrexate dramatically affects the formation of neural tube structures and FA partially reverts this aberrant phenotype. In conclusion, we present a novel model for human NTDs and provide evidence that it is a powerful tool to investigate the molecular mechanisms underlying NTDs, test drugs for therapeutic approaches.

Methotrexate and Valproic Acid Affect Early Neurogenesis of Human Amniotic Fluid Stem Cells from Myelomeningocele

Myelomeningocele (MMC) is a severe type of neural tube defect (NTD), in which the backbone and spinal canal do not close completely during early embryonic development. This condition results in serious morbidity and increased mortality after birth. Folic acid significantly reduces, and conversely, folate antagonist methotrexate (MTX) and valproic acid (VPA) increase the occurrence of NTDs, including MMC. How these pharmacological agents exactly influence the early neurulation process is still largely unclear. Here, we characterized human amniotic fluid-derived stem cells (AFSCs) from prenatally diagnosed MMC and observed an effect of MTX and VPA administration on the early neural differentiation process. We found that MMC-derived AFSCs highly expressed early neural and radial glial genes that were negatively affected by MTX and VPA exposure. In conclusion, we setup a human cell model of MMC to study early neurogenesis and for drug screening purposes. We also proposed the detection of early neural gene expression in AFSCs as an additional MMC diagnostic tool.

Long-term administration of scopolamine interferes with nerve cell proliferation, differentiation and migration in adult mouse hippocampal dentate gyrus, but it does not induce cell death

Long-term administration of scopolamine, a muscarinic receptor antagonist, can inhibit the survival of newly generated cells, but its effect on the proliferation, differentiation and migration of nerve cells in the adult mouse hippocampal dentate gyrus remain poorly understood. In this study, we used immunohistochemistry and western blot methods to weekly detect the biological behaviors of nerve cells in the hippocampal dentate gyrus of adult mice that received intraperitoneal administration of scopolamine for 4 weeks. Expression of neuronal nuclear antigen (NeuN; a neuronal marker) and Fluoro-Jade B (a marker for the localization of neuronal degeneration) was also detected. After scopolamine treatment, mouse hippocampal neurons did not die, and Ki-67 (a marker for proliferating cells)-immunoreactive cells were reduced in number and reached the lowest level at 4 weeks. Doublecortin (DCX; a marker for newly generated neurons)-immunoreactive cells were gradually shortened in length and reduced in number with time. After scopolamine treatment for 4 weeks, nearly all of the 5-bromo-2'-deoxyuridine (BrdU)-labeled newly generated cells were located in the subgranular zone of the dentate gyrus, but they did not migrate into the granule cell layer. Few mature BrdU/NeuN double-labeled cells were seen in the subgranular zone of the dentate gyrus. These findings suggest that long-term administration of scopolamine interferes with the proliferation, differentiation and migration of nerve cells in the adult mouse hippocampal dentate gyrus, but it does not induce cell death.

The roles and regulation of multicellular rosette structures during morphogenesis

Multicellular rosettes have recently been appreciated as important cellular intermediates that are observed during the formation of diverse organ systems. These rosettes are polarized, transient epithelial structures that sometimes recapitulate the form of the adult organ. Rosette formation has been studied in various developmental contexts, such as in the zebrafish lateral line primordium, the vertebrate pancreas, the Drosophila epithelium and retina, as well as in the adult neural stem cell niche. These studies have revealed that the cytoskeletal rearrangements responsible for rosette formation appear to be conserved. By contrast, the extracellular cues that trigger these rearrangements in vivo are less well understood and are more diverse. Here, we review recent studies of the genetic regulation and cellular transitions involved in rosette formation. We discuss and compare specific models for rosette formation and highlight outstanding questions in the field.

Maternal micronutrient imbalance alters gene expression of BDNF, NGF, TrkB and CREB in the offspring brain at an adult age

Micronutrients like folate, vitamin B12, and fatty acids which are interlinked in the one carbon cycle play a vital role in mediating epigenetic processes leading to an increased risk for neurodevelopmental disorders in the offspring. Our earlier study demonstrates that a micronutrient imbalanced diet adversely affects docosahexaenoic acid (DHA) and protein levels of neurotrophins like brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) in the brain and cognition in the offspring by 3 months of age. In this study we attempt to analyze if these effects are a consequence of a change in gene expression of these molecules. Further, we also examined the effect of either a postnatal control diet or a prenatal omega-3 fatty acid supplementation on gene expression in the cortex of the offspring. Pregnant rats were divided into control and five treatment groups at two levels of folic acid (normal and excess folate) in the presence and absence of vitamin B12. Omega-3 fatty acid (eicosapentaenoic acid - EPA+DHA) supplementation was given to vitamin B12 deficient groups. Following delivery, 8 dams from each group were shifted to control diet and remaining continued on the same treatment diet. Our results demonstrate that the imbalanced diet caused a marked reduction in the mRNA levels of BDNF, NGF, TrkB, and cAMP response element-binding protein (CREB). Prenatal omega-3 fatty acid supplementation to the maternal imbalanced diet was able to normalize the mRNA levels of all the above genes. This study demonstrates that a maternal diet imbalanced in micronutrients (folic acid, vitamin B12) influences gene expression of neurotrophins and their signalling molecules and thereby adversely affects the brain of the offspring.

Prenatal omega 3 fatty acid supplementation to a micronutrient imbalanced diet protects brain neurotrophins in both the cortex and hippocampus in the adult rat offspring

OBJECTIVE

Our earlier studies show that maternal diets imbalanced in micronutrients like folic acid and vitamin B12 reduced brain docosahexaenoic acid (DHA) and brain derived neurotrophic factor (BDNF) and nerve growth factor (NGF) in the offspring at birth and postnatal d21. This study followed the offspring till 3 months to examine the hypothesis that impaired brain neurotrophins at birth and d21 due to altered maternal micronutrients can be reversed by prenatal omega 3 fatty acid but not a postnatal control diet leading to altered cognition in adult life.

MATERIALS AND METHODS

Pregnant rats were divided into control and five treatment groups at two levels of folic acid (normal and excess folate) in the presence and absence of vitamin B12 (NFBD, EFB and EFBD). Omega 3 fatty acid supplementation was given to the vitamin B12 deficient groups (NFBDO and EFBDO). Following delivery, 8 dams from each group were shifted to control and remaining continued on same diet.

RESULTS

Imbalance in maternal micronutrients up to 3months decreased DHA, BDNF and NGF in cortex and only BDNF in the hippocampus and impaired cognitive performance. Postnatal control diet normalized BDNF in the cortex but not the hippocampus and also altered cognitive performance. Prenatal omega 3 fatty acid supplementation normalized DHA, BDNF and NGF while long term supplementation was not beneficial only when micronutrients were imbalanced.

CONCLUSION

Patterns established at birth are not totally reversible by postnatal diets and give clues for planning intervention studies for improving brain functioning and cognitive abilities.

Notch signaling maintains neural rosette polarity

Formation of the metazoan body plan requires a complex interplay of morphological changes and patterning, and central to these processes is the establishment of apical/basal cell polarity. In the developing nervous system, apical/basal cell polarity is essential for neural tube closure and maintenance of the neural stem cell population. In this report we explore how a signaling pathway important for nervous system development, Notch signaling, impacts on apical/basal cell polarity in neural differentiation. CSL(-/-) mouse embryos, which are devoid of canonical Notch signaling, demonstrated a neural tube phenotype consistent with cell polarity and convergent extension defects, including deficiencies in the restricted expression of apical polarity markers in the neuroepithelium. CSL(-/-) mouse embryonic stem (ES) cells, cultured at low density, behaved as wild-type in the establishment of neural progenitors and apical specification, though progression through rosette formation, an in vitro correlate of neurulation, required CSL for correct maintenance of rosette structure and regulation of neuronal differentiation. Similarly, acute pharmacological inhibition of Notch signaling led to the breakdown of neural rosettes and accelerated neuronal differentiation. In addition to functional Notch signaling, rosette integrity was found to require actin polymerization and Rho kinase (ROCK) activity. Disruption of rosettes through inhibition of actin polymerization or ROCK activity, however, had no effect on neuronal differentiation, indicating that rosette maintenance is not a prerequisite for normal neuronal differentiation. In conclusion, our data indicate that Notch signaling plays a role not only in differentiation, but also in organization and maintenance of polarity during development of the early nervous system.

Effect of low dose bisphenol A on the early differentiation of human embryonic stem cells into mammary epithelial cells

It has been previously reported that bisphenol A (BPA) can disturb the development of mammary structure and increase the risk of breast cancer in experimental animals. In this study, an in vitro model of human embryonic stem cell (hESC) differentiation into mammary epithelial cells was applied to investigate the effect of low dose BPA on the early stages of mammogenesis. A newly established hESC line was directionally differentiated into mammary epithelial cells by a well-established three-dimensional (3D) culture system. The differentiated mammary epithelial cells were characterized by immunofluorescence and western blotting assay, and were called induced differentiated mammary epithelial cells (iDMECs) based on these data. The hESCs were treated with low doses of BPA range 10(-9)-10(-6)M during the differentiation process, with DMSO as the solvent control and 17-β-estrodiol (E2) as the estrogen-positive control. Our results showed that low dose BPA and E2 could influence the mammosphere area of iDMECs and upregulate the expression level of Oct4 and Nanog proteins, while only BPA could downregulate the expression of E-cadherin protein. Taken together, this study provides some insights into the effects of low dose BPA on the early differentiation stage of mammary epithelial cells and suggests an easier canceration status of iDMECs under the effect of low dose BPA during its early differentiation stage.