Project description:Firemaster® 550 (FM 550) is a flame retardant (FR) mixture that has become one of the most commonly used FRs in foam-based furniture and baby products. Human exposure to this commercial mixture, comprised of brominated and organophosphate components, is widespread. We have repeatedly shown that developmental exposure can lead to sex-specific behavioral effects in rats. Accruing evidence of endocrine disruption and potential neurotoxicity have raised concerns regarding the neurodevelopmental effects of FM 550 exposure, but the specific mechanisms of action remains unclear. Additionally, we observed significant, and in some cases sex-specific, accumulation of FM 550 in placental tissue following gestational exposure. Because the placenta is an important source of hormones and neurotransmitters for the developing brain, it may be a critical target of toxicity to consider in the context of developmental neurotoxicity. Using a mixture of targeted and exploratory approaches, the goal of the present study was to identify possible mechanisms of action in the developing forebrain and placenta. Wistar rat dams were orally exposed to FM 550 (0, 300, or 1,000 µg/day;) for 10 days during gestation and placenta and fetal forebrain tissue collected for analysis. In placenta, evidence of endocrine, inflammatory, and neurotransmitter signaling pathway disruption was identified. Notably, 5-HT turnover was reduced in placental tissue and fetal forebrains indicating that 5-HT signaling between the placenta and the embryonic brain may be disrupted. These findings demonstrate that environmental contaminants, like FM 550, have the potential to impact the developing brain by disrupting normal placental functions.
Project description:There is a growing need to understand the potential neurotoxicity of organophosphate ester flame retardants (OPFRs) and plasticizers because use and, consequently, human exposure, is rapidly expanding. We have previously shown in rats that developmental exposure to the commercial FR mixture Firemaster® 550 (FM 550), which contains OPFRs, results in sex-specific behavioral effects, and identified the placenta as a potential target of toxicity. The placenta is a critical coordinator of fetal growth and neurodevelopment, and a source of neurotransmitters (NTs) for the developing brain. We have shown in rats and humans that FRs accumulate in placental tissue, and induce functional changes, including altered neurotransmitter (NT) production. Here we sought to establish if OPFRs (triphenyl phosphate, TPHP, and a mixture of isopropylated triarylphosphate isomers, ITPs) alter placental function and fetal forebrain development, with disruption of tryptophan (Trp) metabolism as a primary pathway of interest. Wistar rat dams were orally exposed to OPFRs (0, 500, 1,000, or 2,000 μg/day) or a serotonin (5-HT) agonist (5-MT) for 14 days during gestation and placenta and fetal forebrain tissues collected for analysis by transcriptomics and metabolomics. Relative abundance of genes responsible for the transport and synthesis of placental 5-HT were disrupted, and multiple neuroactive metabolites in the 5-HT and kynurenine (Kyn) metabolic pathways were upregulated. Additionally, 5-HTergic projections were significantly longer in the fetal forebrains of exposed males. These findings suggest that OPFRs have the potential to impact the 5-HTergic system in the fetal forebrain by disrupting placental Trp metabolism.
Project description:2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) causes the many forms of reproductive toxicity, such as defects in sexual behaviors, in pups of which mother is exposed to this substance at lower doses. However, the mechanism underlying these defects remains to be clarified in spite of many researches conducted so far. Our previous studies have revealed that maternal treatment with TCDD attenuates the production of pituitary gonadotropins [luteinizing hormone (LH) and follicle-stimulating hormone] in the late fetuses, leading to the impairment of sexual behavior in adulthood. To identify the target genes for a fetal reduction in gonadotropin β-subunit, we performed DNA microarray analysis using the fetal pituitary and its regulatory organ, the hypothalamus. The result showed that TCDD induced histone deacetylases (HDACs), and altered the expression of genes including gonadotropin-releasing hormone and activin signaling in the fetal pituitary. Moreover, our data indicated that the increased deacetylation of histone due to HDAC induction plays a critical role for a dioxin-induced attenuation of LHβ in the fetal pituitary. This study suggests a novel molecular mechanism explaining dioxin-produced reproductive toxicity. Pregnant Wistar rats were orally treated with TCDD (1 µg/kg in corn oil) at gestational day (GD)15. Then, the total RNA was extracted from the fetal pituitary and hypothalamus at GD20. To identify the target genes the alteration of which contributes to a reduction in fetal gonadotropin β-subunit, the profile of gene expression was analyzed using the Illumina RatRef-12 Expression BeadChip.
Project description:Hyperactivated mTOR signaling in the developing brain by mutation of TSC1 genes has multiple forms of pathology including tuberous sclerosis complex (TSC). To examine the downstream networks affected in the developing brain by hyperactivated mTOR signaling, we performed an integrated analysis of transcriptomic and proteomic analysis of forebrain of wild-type and TSC1/Emx1-Cre mouse. Our results provide novel and fundamental molecular bases for understanding hyperactivaed mTOR signaling-induced brain defects which can in turn facilitate identification of potential diagnostic markers and therapeutic targets for mTOR signaling-related neurological disorders.
Project description:Oligodendrogenesis in the human central nervous system has been mainly observed at the second trimester of gestation, a much later developmental stage compared to mouse. Here we characterize the transcriptomic neural diversity in the human forebrain at post conceptual weeks (PCW) 8 to 10, using single-cell RNA-Seq. We find evidence of the emergence of a first wave of oligodendrocyte lineage cells as early as PCW 8, which we also confirm at the epigenomic level with single-cell ATAC-Seq. Using regulatory network inference, we predict key transcriptional events leading to the specification of oligodendrocyte precursor cells (OPCs). Moreover, by profiling the spatial expression of fifty key genes using In Situ Sequencing (ISS), we identify regions in the human ventral fetal forebrain where oligodendrogenesis first occurs. Our results indicate evolutionary conservation of the first wave of oligodendrogenesis between mouse and human and describe regulatory mechanisms involved in human OPC specification.