Project description:Neural tube defects (NTD) occur in 3000 births per year in the US. Several risk factors have been proposed for NTDs including both first hand and passive smoking during the periconceptual period. Previously we reported an increased frequency of cervical region NTD in a chicken model of prenatal nicotine exposure (Bohn, Humphrey et al. 2014; Humprey, Bohn et al. 2014). Here, we will reveal the mechanisms of the insult. The specific aims include: 1) Evaluation of the gene expression changes in the chicken model of nicotine exposure that we developed previosly. Such genome-wide analysis of the expression allows to collect very detailed data regarding the drug impact. To our knowlidge, comparable analysis of nicotine induced changes in gene expression during development of any species has never been conducted. 2) Evaluation of nicotine induced alterations in tadpoles (Xenopus tropica). The frogs will be treated in a manner similar to chicken (the same drug doses and a matched time of sacrifice) and analyzed both histologically and for gene expression. Incorporation of a different group of vertebrates in this study is essential for dissecting the evolutionary conserved role this pathway of interest in development which is another strong aspect of this proposal. We believe, that our comparative approach will allow more effective extrapolation of data from animal models to humans and better understanding of the evolutionary process. Nicotine is one of the most common developmental insults in humans. The consequences of this exposure are well-documented. However, the affected pathways are unknown. The identification of the mechanisms of nicotine induced alterations proposed here is vital for development of better treatment strategies.
Project description:BACKGROUND: Development of the neural tube is a highly orchestrated process relying on precise, spatio-temporal expression of numerous genes as well as hierarchies of signal transduction and gene regulatory networks. Disruption of expression of a number of genes participating in these networks is believed to underlie developmental anomalies such as neural tube defects (NTDs) resulting from anomalous neural tube morphogenesis. MicroRNAs (miRNAs), a large family of noncoding RNAs, have been shown to function as gene silencers, and thus, are key modulators of cell and tissue differentiation. To elucidate potential roles of miRNAs in murine neural tube development, miRNA gene expression profiling has been utilized in the current study, to garner novel and in-depth knowledge on the expression and regulation of genes encoding miRNAs as well as their potential target genes governing maturation of the mammalian neural tube. METHODS: With the aim of identifying differentially expressed miRNAs during mammalian neural tube ontogenesis, miRNA expression profiles from gestation day (GD) -8.5, -9.0 and -9.5 murine neural tube tissue were compared utilizing miRXplore™ microarrays from Miltenyi Biotech GmbH. Gene expression changes observed in microarray analysis were verified by TaqManTM quantitative Real-Time PCR. clValid R package and the UPGMA (hierarchical) clustering method were utilized for cluster analysis of the microarray data. Functional associations among selected miRNAs were examined exploiting Ingenuity Pathway Analysis. RESULTS: Expression of approximately 12% of the 609 murine miRNA genes examined was detected in murine neural tube tissues from GD -8.5, -9.0 and -9.5. Clustering analysis revealed several developmentally regulated clusters among these expressed genes. MicroRNA target analysis enabled identification of a panoply of protein-coding target genes of the differentially expressed miRNAs within such clusters. Interestingly, many of these target genes have been shown to be associated with vital cellular processes such as cell proliferation, cell adhesion, cell migration, differentiation, apoptosis and epithelial-mesenchymal transformation, all of which are essential for normal neural tube development. Utilization of Ingenuity Pathway Analysis (IPA; Ingenuity Systems) allowed identification of interactive biological networks connecting differentially expressed miRNAs and their target genes highlighting functional relationships. CONCLUSIONS: In the present study, a unique gene expression signature of a range of miRNAs in embryonic neural tube tissue was delineated. Analysis of miRNA target genes and gene interaction pathways emphasized that expression of numerous protein-encoding genes, indispensable for normal neural tube morphogenesis, may be regulated by specific miRNAs.
Project description:At an incidence of approximately 1/1000 births, neural tube defects (NTDs) comprise one of the most common and devastating congenital disorders. In an attempt to enhance and expand our understanding of neural tube closure, we undertook a high-throughput gene expression analysis of the neural tube as it was forming in the mouse embryo. Open and closed sections of the developing neural tube were micro-dissected from mouse embryos, and hybridized to Affymetrix mouse expression arrays. Clustering of genes differentially regulated in open and closed sections of the developing neural tube highlighted molecular processes previously recognized to be involved in neural tube closure and neurogenesis. Analysis of the genes in these categories identified potential candidates underlying neural tube closure. In addition, we identified approximately 25 novel genes, of unknown function, that were significantly up-regulated in the closed neural tube. Based on their expression patterns in the developing neural tube, five novel genes are proposed as interesting candidates for involvement in neurogenesis. The high-throughput expression analysis of the neural tube as it forms allows for better characterization of pathways involved in neural tube closure and neurogenesis, and hopefully will strengthen the foundation for further research along the pathways dictating neural tube development.
Project description:The inner ear utilizes sensory hair cells as mechano-electric transducers for sensing sound and balance. In mammals, these hair cells lack the capacity for regeneration. Unlike mammals, hair cells from non-mammalian vertebrates, such as birds, can be regenerated throughout the life of the organism making them a useful model for studying inner ear genetics pathways. The zinc finger transcription factor GATA3 is required for inner ear development and mutations cause sensory neural deafness in humans. In the avian cochlea GATA3 is expressed throughout the sensory epithelia; however, expression is limited to the striola of the utricle. The striola corresponds to an abrupt change in morphologically distinct hair cell types and a 180° shift in hair cell orientation. We used 3 complimentary approaches to identify potential downstream targets of GATA3 in the avian utricle. Specifically we used microarray expression profiling of GATA3 knockdown by siRNA and GATA3 over-expression treatments as well as direct comparisons of GATA3 expressing cells from the striola and non GATA3 expressing cells from the extra-striola.
Project description:At an incidence of approximately 1/1000 births, neural tube defects (NTDs) comprise one of the most common and devastating congenital disorders. In an attempt to enhance and expand our understanding of neural tube closure, we undertook a high-throughput gene expression analysis of the neural tube as it was forming in the mouse embryo. Open and closed sections of the developing neural tube were micro-dissected from mouse embryos, and hybridized to Affymetrix mouse expression arrays. Clustering of genes differentially regulated in open and closed sections of the developing neural tube highlighted molecular processes previously recognized to be involved in neural tube closure and neurogenesis. Analysis of the genes in these categories identified potential candidates underlying neural tube closure. In addition, we identified approximately 25 novel genes, of unknown function, that were significantly up-regulated in the closed neural tube. Based on their expression patterns in the developing neural tube, five novel genes are proposed as interesting candidates for involvement in neurogenesis. The high-throughput expression analysis of the neural tube as it forms allows for better characterization of pathways involved in neural tube closure and neurogenesis, and hopefully will strengthen the foundation for further research along the pathways dictating neural tube development. Embryos were dissected at days E8.5 and E9.5, and the neuroepithelium/ neural tube were mechanically detached from underlying tissues, and then separated into two regions: 1) M-bM-^@M-^\open neuroepitheliumM-bM-^@M-^]: neuroepithelial tissue caudal to the open/closed junction, and 2) M-bM-^@M-^\closed neural tubeM-bM-^@M-^], extending from a somiteM-bM-^@M-^Ys breadth rostral to the open/closed junction, up to the level of the fifth- or sixth-to-last somite. Samples consisted of biological triplicates of RNA extract from the above tissues (pooled by litter, and representing a total of 111 embryos): E8.5 open neuroepithelium, E8.5 closed neural tube, E9.5 open neuroepithelium, and E9.5 closed neural tube. Thus, a total of 12 samples (representing 111 embryos) were hybridized to the GeneChip Mouse Genome 430 2.0 Array (Affymetrix Inc., Santa Clara, CA, USA). One of the samples (06, closed E8.5) deviated significantly from the others in quality assessment and was therefore removed from subsequent analysis and not submitted to GEO.