Detection of abnormal behaviors in prenatal Poly(I:C) exposed mice in a group-rearing environment.

During pregnancy, the maternal environment is critical for normal ontogeny and central nervous system development. Occasionally, prenatal exposure to environmental factors affects tissue architecture and functional development of the brain, which causes developmental disorders, including disorders of the autism spectrum. One of these environmental factors is the exposure to infectious diseases during pregnancy. In this study, we generated mice with infectious disease-induced inflammation by prenatal exposure to 200 µg/kg polyinosinic-polycytidylic acid sodium salt [Poly(I:C)] at embryonic day 12.5 and analyzed their phenotypes on 30-weeks-old. We attempted to detect abnormalities in spontaneous activity and social interaction, which may be indicators of developmental disorder-like behavioral abnormalities, in free-ranging behaviors in multiple rearing environments using multiple animal positioning systems and UMATracker in mice with fetal inflammation. Increased spontaneous activity and abnormal social interactions were observed in mice in the Poly(I:C)-treated group compared with those in the control group. Prenatal exposure to Poly(I:C) increased motor activity and decreased social interaction, and social behavior in prenatally treated mice in a multiple-individual rearing environment. Poly(I:C) exposure during the fetal period resulted in developmental disorder-like behavioral abnormalities, such as increased activity and abnormal social interactions, even after maturation in a multiple-individual rearing environment. This experimental method may provide a new way to analyze the behavior of mouse models of developmental disorders in a multiple-individual rearing environment, in which free-ranging behavior is possible.

Epigenetics and Neuroinflammation Associated With Neurodevelopmental Disorders: A Microglial Perspective.

Neuroinflammation is a cause of neurodevelopmental disorders such as autism spectrum disorders, fetal alcohol syndrome, and cerebral palsy. Converging lines of evidence from basic and clinical sciences suggest that dysregulation of the epigenetic landscape, including DNA methylation and miRNA expression, is associated with neuroinflammation. Genetic and environmental factors can affect the interaction between epigenetics and neuroinflammation, which may cause neurodevelopmental disorders. In this minireview, we focus on neuroinflammation that might be mediated by epigenetic dysregulation in microglia, and compare studies using mammals and zebrafish.

Prenatal and postnatal bisphenol A exposure inhibits postnatal neurogenesis in the hippocampal dentate gyrus.

Bisphenol A (BPA), an endocrine disruptor with estrogenic effects, is widely used as a raw material for manufacturing polycarbonate plastic and epoxy resins. Prenatal and postnatal exposure to BPA affects brain morphogenesis. However, the effects of prenatal and postnatal BPA exposure on postnatal neurogenesis in mice are poorly understood. In this study, we developed a mouse model of prenatal and postnatal BPA exposure and analyzed its effects on hippocampal neurogenesis. The hippocampal dentate gyrus is vulnerable to chemical exposure, as neurogenesis continues in this region even after birth. Our results showed that in mice, prenatal and postnatal BPA exposure decreased the number of type-1, 2a, 2b, and 3 neural progenitor cells, as well as in granule cells, in the hippocampal dentate gyrus on postnatal days 16 and 70. The effect of prenatal and postnatal BPA exposure on neural progenitors were affected at all differentiation stages. In addition, prenatal and postnatal BPA exposure affects the maintenance of long-term memory on postnatal day 70. Our results suggest that neurodevelopmental toxicity due to prenatal and postnatal BPA exposure might affect postnatal morphogenesis and functional development of the hippocampal dentate gyrus.

Postnatal di-2-ethylhexyl phthalate exposure affects hippocampal dentate gyrus morphogenesis.

Di-2-ethylhexyl phthalate (DEHP) is the most commonly used phthalate for the production of flexible polyvinyl chloride. Recent studies in humans reported a widespread DEHP exposure, raising concerns in infants whose metabolic and excretory systems are immature. DEHP is a potential endocrine-disrupting chemical, but the effects of postnatal DEHP exposure on neuronal development are unclear. The dentate gyrus (DG) is critical in the consolidation of information from short- to long-term memory, as well as spatial learning. We evaluated neurodevelopmental toxicity due to neonatal DEHP exposure by assessing neurogenesis in the DG. Newborn mice were orally administered DEHP from postnatal day (PND) 12 to 25. We performed immunostaining using neuronal markers at different stages to assess whether DEHP exposure affects neurons at specific differentiation stages at PND 26 and PND 110. We found that in mice, postnatal DEHP exposure led to a decrease in the number of Type-1, -2a, -2b, and -3 neural progenitor cells, as well as granule cells in the hippocampal DG at PND 26. Further, the results showed that neural progenitor cell proliferation and differentiation were also reduced in the hippocampal DG of the DEHP-exposed mice. However, no effect on memory and learning was observed. Overall, our results suggest that neurodevelopmental toxicity due to postnatal DEHP exposure might affect postnatal DG morphogenesis.

Bisphenol A exposure induces increased microglia and microglial related factors in the murine embryonic dorsal telencephalon and hypothalamus.

Bisphenol A (BPA) is a widely used compound in the food packaging industry. Prenatal exposure to BPA induces histological abnormalities in the neocortex and hypothalamus in association with abnormal behaviors. Yet, the molecular and cellular neurodevelopmental toxicological mechanisms of BPA are incompletely characterized on neuroinflammatory-related endopoints. To evaluate the neurodevelopmental effects of BPA exposure in mouse embryos, we examined microglial numbers as well as the expression of microglial-related factors in the E15.5 embryonic brain. BPA-exposed embryos exhibited significant increases in Iba1-immunoreactive microglial numbers in the dorsal telencephalon and the hypothalamus compared to control embryos. Further, the expression levels of microglial markers (Iba1, CD16, iNOS, and CD206), inflammatory factors (TNFα and IL4), signal transducing molecules (Cx3Cr1 and Cx3Cl1), and neurotrophic factor (IGF1) were altered in BPA-exposed embryos. These findings suggest that BPA exposure increases microglial numbers in the brain and alters the neuroinflammatory status at a transcriptional level. Together, these changes may represent a novel target for neurodevelopmental toxicity assessment after BPA exposure.

Mechanisms underlying neuro-inflammation and neurodevelopmental toxicity in the mouse neocortex following prenatal exposure to ethanol.

Fetal alcohol spectrum disorders (FASD) constitute a wide range of disorders that arise from prenatal exposure to ethanol (EtOH). However, detailed reports regarding the adverse effects of prenatal EtOH exposure on neocortical morphology and its underlying pathogenic mechanisms are limited. In the present study, we aimed to characterize the anatomical abnormalities of neocortical development and their correlation with microglial properties and neuro-inflammation in a mouse model of FASD. We evaluated the development and maturation of the neocortex in ICR mice prenatally exposed to 25% (w/v) EtOH using histological and molecular analyses. Reduced proliferation and excessive cell death were observed in the dorsal telencephalon. Abnormal neuronal distribution, layer formation, and dopaminergic neuronal projections were observed in the neocortex. Disruption of microglial differentiation (M1/M2 microglial ratio) and abnormal expression of pro-inflammatory and neurotrophic factors were induced, and these abnormalities were ameliorated by co-treatment with an anti-inflammatory drug (pioglitazone). FASD model mice displayed histological abnormalities, microglial abnormalities, and neuro-inflammation in both the embryonic and newborn stages. Thus, anti-inflammatory therapeutics may provide a novel preventive approach for the treatment of FASD.

Expression of Kisspeptin in Gonadotrope Precursors in the Mouse Pituitary during Embryonic and Postnatal Development and in Adulthood.

BACKGROUND: Kisspeptins are important regulators of the development and function of the hypothalamic-pituitary-gonadal axis. However, the importance of kisspeptin at the pituitary level is unclear. METHODS: We examined the expression profile of kisspeptin in the mouse pituitary during development and in adulthood using RT-PCR, quantitative PCR and immunohistochemistry. RESULTS: Kiss1 mRNA was detected in both embryonic and postnatal pituitaries. Kisspeptin-immunoreactive (+) cells were detected from embryonic day (E) 13.5 throughout adulthood, being localized to the rostroventral portion in the anterior pituitary (AP) in embryos, and also to the dorsocaudal AP postnatally. A large proportion of kisspeptin+ cells were double-labeled with gonadotrope markers including Foxl2, SF-1, and LHß, and the percentage of LHß+ cells in kisspeptin+ cells increased during development. No kisspeptin+ cells were positive for the proliferating cell marker MCM7 (minichromosome maintenance protein 7), but a few kisspeptin+ cells co-expressed the stem/progenitor cell marker Sox2. Kisspeptin expression was similar between sexes and between agonadal SF-1 knockout embryos and wild-type littermates. Kiss1 mRNA levels were not significantly different between sexes or during early postnatal development, but levels in females increased when puberty began and were significantly higher than in males at postpubertal ages. CONCLUSIONS: These results suggest that kisspeptin is expressed in gonadotrope precursors during gonadotrope differentiation, and that kisspeptin expression begins soon after the initiation of αGSU production and is extinguished soon after the initiation of LH production. Furthermore, pituitary kisspeptin expression may be regulated in a gonad-independent manner during development, but may be associated with gonadotrope function in adulthood.

Prenatal exposure to di(2-ethylhexyl) phthalate impairs development of the mouse neocortex.

Di(2-ethylhexyl) phthalate (DEHP) is currently the most commonly used phthalate for the production of flexible polyvinyl chloride. Phthalates including DEHP have been labeled as potential endocrine disruptors. The effect on the development of the neocortex, however, is unknown. To evaluate the neurodevelopmental effects of prenatal DEHP exposure at 1 and 100mg/kg/day or 100 and 500mg/kg/day in fetal and newborn mice, we performed a detailed histologic analysis of the developing dorsal telencephalon and neocortex. The observation of fetuses exposed to DEHP revealed reductions of proliferation and neurogenesis (1 and 100mg/kg) and an increase in cell death (500mg/kg). In addition, the newborns prenatally exposed to DEHP showed an abnormal neuronal distribution and a decrease in neurons. These findings suggest that prenatal DEHP exposure induces neurodevelopmental toxicity associated with the neural stem cell niche and corticogenesis.

Filamin A interacting protein plays a role in proper positioning of callosal projection neurons in the cortex.

The callosal connections between the two hemispheres of the neocortex are altered in certain psychiatric disorders including schizophrenia. However, how and why the callosal connection is impaired in patients suffering from psychiatric diseases remain unclear. Filamin A interacting protein (FILIP), whose alteration through mutation relates to schizophrenic pathogenesis, binds to actin-binding proteins and controls neurotransmission. Because cortical excitatory neurons, including callosal projection neurons, migrate to the cortical plate during development, with the actin-binding proteins playing crucial roles during migration, we evaluated whether FILIP is involved in the development of the callosal projection neurons by histological analysis of Filip-knockout mice. The positioning of the callosal projection neurons, especially those expressing Plxnd1, in the superficial layer of the cortex is disturbed in these mice, which suggests that FILIP is a key molecule that links callosal projections to the pathogenesis of brain disorders.

Extraction of DNA from human embryos after long-term preservation in formalin and Bouin's solutions.

The "Kyoto Collection of Human Embryos" at Kyoto University was begun in 1961. Although morphological analyses of samples in the Kyoto Collection have been performed, these embryos have been considered difficult to genetically analyze because they have been preserved in formalin or Bouin's solution for 20-50 years. Owing to the recent advances in molecular biology, it has become possible to extract DNA from long-term fixed tissues. The purpose of this study was to extract DNA from wet preparations of human embryo samples after long-term preservation in fixing solution. We optimized the DNA extraction protocol to be suitable for tissues that have been damaged by long-term fixation, including DNA-protein crosslinking damage. Diluting Li2 CO3 with 70% ethanol effectively removed picric acid from samples fixed in Bouin's solution. Additionally, 20.0 mg/mL proteinase was valuable to lyse the long-term fixed samples. The extracted DNA was checked with PCR amplification using several sets of primers and sequence analysis. The PCR products included at least 295- and 838-bp amplicons. These results show that the extracted DNA is applicable for genetic analyses, and indicate that old embryos in the Kyoto Collection should be made available for future studies. The protocol described in this study can successfully extract DNA from old specimens and, with improvements, should be applicable in research aiming to understand the molecular mechanisms of human congenital anomalies.

Involvement of SF-1 in neurogenesis and neuronal migration in the developing neocortex.

The nuclear receptor steroidogenic factor-1 (SF-1) plays essential roles in the development and function of the endocrine and reproductive systems. During embryogenesis, SF-1 is expressed in the ventromedial hypothalamic nucleus (VMH) and regulates the migration and terminal differentiation of the VMH neurons. Additionally, in situ hybridization data indicated SF-1 expression in the dorsal telencephalon at embryonic day (E) 13.5. In this study, we investigated the neocortical development in SF-1 knockout (KO) mouse embryos. The number of neurons was increased in the intermediate/subventricular zones and decreased in the cortical plate in the SF-1 KO embryos. SF-1 KO embryos produced more neural stem/progenitor cells, especially apical progenitor cells, and showed abnormal radial glial fiber morphology. The increase in neural stem/progenitor cells was caused by an increased S-phase fraction in the proliferative cells and the inhibition of cell cycle exit in these cells. The mRNA expression of the estrogen receptor ESRα was up-regulated and that of the estrogen synthetase Cyp19a1 was down-regulated in the dorsal telencephalon of SF-1 KO embryos. We showed that SF-1 is expressed in the dorsal telencephalon at E15.5 and E18.5, but not in adult animals. Our data demonstrated that SF-1 is involved in cell cycle regulation, neurogenesis, and neuronal migration via controlling the estrogen signaling for proper neocortical development.

DBZ regulates cortical cell positioning and neurite development by sustaining the anterograde transport of Lis1 and DISC1 through control of Ndel1 dual-phosphorylation.

Cell positioning and neuronal network formation are crucial for proper brain function. Disrupted-in-Schizophrenia 1 (DISC1) is anterogradely transported to the neurite tips, together with Lis1, and functions in neurite extension via suppression of GSK3ß activity. Then, transported Lis1 is retrogradely transported and functions in cell migration. Here, we show that DISC1-binding zinc finger protein (DBZ), together with DISC1, regulates mouse cortical cell positioning and neurite development in vivo. DBZ hindered Ndel1 phosphorylation at threonine 219 and serine 251. DBZ depletion or expression of a double-phosphorylated mimetic form of Ndel1 impaired the transport of Lis1 and DISC1 to the neurite tips and hampered microtubule elongation. Moreover, application of DISC1 or a GSK3ß inhibitor rescued the impairments caused by DBZ insufficiency or double-phosphorylated Ndel1 expression. We concluded that DBZ controls cell positioning and neurite development by interfering with Ndel1 from disproportionate phosphorylation, which is critical for appropriate anterograde transport of the DISC1-complex.

Filamin A-interacting protein (FILIP) is a region-specific modulator of myosin 2b and controls spine morphology and NMDA receptor accumulation.

Learning and memory depend on morphological and functional changes to neural spines. Non-muscle myosin 2b regulates actin dynamics downstream of long-term potentiation induction. However, the mechanism by which myosin 2b is regulated in the spine has not been fully elucidated. Here, we show that filamin A-interacting protein (FILIP) is involved in the control of neural spine morphology and is limitedly expressed in the brain. FILIP bound near the ATPase domain of non-muscle myosin heavy chain IIb, an essential component of myosin 2b, and modified the function of myosin 2b by interfering with its actin-binding activity. In addition, FILIP altered the subcellular distribution of myosin 2b in spines. Moreover, subunits of the NMDA receptor were differently distributed in FILIP-expressing neurons, and excitation propagation was altered in FILIP-knockout mice. These results indicate that FILIP is a novel, region-specific modulator of myosin 2b.

Newborn mice exposed prenatally to bisphenol A show hyperactivity and defective neocortical development.

The central nervous system is especially susceptible to toxic insults during development. Prenatal administration of bisphenol A (BPA) induces histologic anomalies in the dorsal telencephalon of the embryo. Whether these anomalies affect the morphogenesis and maturation of neuronal function of the newborn neocortex, however, is unknown. To evaluate the neurodevelopmental and behavioral effects of prenatal BPA exposure at 20 and 200µg/kg/day in newborn mice, we performed a detailed histologic analysis of the neocortex and tested for the presence of behavioral abnormalities in newborn mice prenatally exposed to BPA using our newly developed behavioral test. Observations of newborn mice prenatally exposed to BPA revealed abnormal neuronal distribution and layer formation, hypoplasia of layer 6b, and abnormal dopaminergic neuronal projections in the neocortex. Further, the newborn mice exhibited hyperactivity. These findings suggest that prenatal BPA exposure induces neurobehavioral toxicity associated with abnormal dopaminergic neuronal projections, and abnormal corticogenesis and lamination. Histologic and behavioral analyses of newborn mice are considered useful for assessing the neurodevelopmental and behavioral toxicity of chemicals.

Neurobehavioral evaluation of mouse newborns exposed prenatally to low-dose bisphenol A.

There have been few neurobehavioral toxicology studies on newborn animals. Thus, we developed a mouse newborn behavioral testing method for evaluating the risk of neurotoxicity of environmental toxicants, by means of determining the newborn's motor activity applying the tare function of an analytical balance. Motor activities including crawling, pivoting, righting or tremors of mouse newborns were evaluated. Tremors of newborns of dams exposed to bisphenol A at 2, 20 or 200 µg/kg/day on days 5 through 18 of gestation were significantly increased when evaluated on postnatal day 1, as well as those of newborns exposed prenatally to diethylstilbestrol at 0.5 µg/kg/day. We suggest that our developed testing method may provide a useful addition to neurobehavioral assessment in very young rodents exposed to environmental hormone mimics.

Smoothened controls cyclin D2 expression and regulates the generation of intermediate progenitors in the developing cortex.

Translocation of the Smoothened to the cell membrane is critical for sonic hedgehog activity. However, the biological importance of Smoothened itself has not been fully studied. To address this issue, we disabled Smoothened specifically in the dorsal telencephalon. Birth-date analysis and layer marker expression patterns revealed the slightly impaired development of the superficial layer neurons in the embryos of Emx1-Cre; Smoothened(fl/-) conditional knockout mice. Further analysis of the mutant embryos revealed a decrease in the number of intermediate progenitor cells. In the knockout mice, the expression of cyclin D2, but not cyclin D1 or cyclin E, was reduced in the dorsal telencephalon. In addition, the projections of dopaminergic neurons were affected during development, and the number of activated astrocytes was increased in the neocortex of the mutant mice. Our data suggest that Smoothened signaling, acting through cyclin D2, is critical for the proper development and maturation of the neocortex.

WAVE2-Abi2 complex controls growth cone activity and regulates the multipolar-bipolar transition as well as the initiation of glia-guided migration.

Glia-guided migration (glia-guided locomotion) during radial migration is a characteristic yet unique mode of migration. In this process, the directionality of migration is predetermined by glial processes and not by growth cones. Prior to the initiation of glia-guided migration, migrating neurons transform from multipolar to bipolar, but the molecular mechanisms underlying this multipolar-bipolar transition and the commencement of glia-guided migration are not fully understood. Here, we demonstrate that the multipolar-bipolar transition is not solely a cell autonomous event; instead, the interaction of growth cones with glial processes plays an essential role. Time-lapse imaging with lattice assays reveals the importance of vigorously active growth cones in searching for appropriate glial scaffolds, completing the transition, and initiating glia-guided migration. These growth cone activities are regulated by Abl kinase and Cdk5 via WAVE2-Abi2 through the phosphorylation of tyrosine 150 and serine 137 of WAVE2. Neurons that do not display such growth cone activities are mispositioned in a more superficial location in the neocortex, suggesting the significance of growth cones for the final location of the neurons. This process occurs in spite of the "inside-out" principle in which later-born neurons are situated more superficially.

Newly developed mouse newborn behavioral testing method for evaluating the risk of neurotoxicity of environmental toxicants.

Although there have been a vast number of behavioral toxicology studies carried out on adult mice and rats, there have been few neurobehavioral studies utilizing their newborn animals. Thus, we developed a mouse newborn behavioral testing method for evaluating the risk of neurotoxicity of chemicals, by means of determining the newborn's activity using the tare function of an analytical balance. The unstable weighing values resulting from movement of the newborn on the balance recorded by a personal computer every 0.1 s, and the total activities of a newborn from the start time of weighing to individual times of evaluation were calculated. In addition, we confirmed the usefulness of our method by determining the activity of mouse newborns with microcephaly induced by prenatal exposure to a neurotoxicant, methylnitrosourea.

Developmental effects of oral exposure to diethylstilbestrol on mouse placenta.

Placental growth and function are of biological significance in that placental tissue promotes prenatal life and the maintenance of pregnancy. Exposure to synthetic estrogens causes embryonic mortality and placental growth restriction in mice. The aim of the present study was to examine the effects of diethylstilbestrol (DES) on placenta in mice. DES at 1, 5, 10 or 15 µg kg(-1) day(-1) , or 17ß-estradiol (E2 ) at 50 µg kg(-1) day(-1) , was administered orally to ICR mice on days 4 through to 8 of gestation. Expression of ERα, ERß, ERRß or ERRγ mRNA in the junctional or labyrinth zone of the placentas on day 13 was assessed using RT-PCR, as well as the embrynic mortality, embryonic and placental weight, histological changes of labyrinth and ultrastructural changes of the trophoblast giant cells (TGCs). Embryo mortalities in the DES 10 and 15 µg kg(-1) day(-1) groups were markedly increased. No significant changes in embryonic and placental weight were observed in any DES- or E2 -exposed groups. Expression of ERα mRNA in the junctional zone with male embryos in the 5 µg kg(-1) day(-1) group was significantly higher than that in the control, whereas expression was not determined in the 15 µg kg(-1) day(-1) group. Histological observation revealed that the placentas exposed to DES at 10 µg kg(-1) day(-1) lacked the developing labyrinth. Ultrastructural observation of the TGCs showed poor rough-surfaced endoplasmic reticulum in the DES 10 µg kg(-1) day(-1) group. The present data suggest that developmental changes induced by DES may be related to interference with the nutrition and oxygen exchange between mother and embryo or decreased protein synthesis, resulting in a high frequency of embryo mortality.