The posterior gut of the Drosophila embryo, consisting of hindgut and Malpighian tubules, provides a simple,well-defined system where it is possible to use a genetic approach to define components essential for epithel...The posterior gut of the Drosophila embryo, consisting of hindgut and Malpighian tubules, provides a simple,well-defined system where it is possible to use a genetic approach to define components essential for epithelial morphogenesis.We review here the advantages of Drosophila as a model genetic organism, the morphogenesis of the epithelial structures of the posterior gut, and what is known about the genetic requirements to form these structures.In overview, primordia are patterned by expression of hierarchies of transcription factors; this leads to localized expression of cell signaling molecules, and finally, to the least understood step: modulation of cell adhesion and cell shape. We describe approaches to identify additional genes that are required for morphogenesis of these simple epithelia, particularly those that might play a structural role by affecting cell adhesion and cell shape.展开更多
The large-scale convergence of homotopy parametric inversion method on the water quality model parameters calculated was used,with application in parametric inversion calculation of total phosphorus of Beijing Miyun R...The large-scale convergence of homotopy parametric inversion method on the water quality model parameters calculated was used,with application in parametric inversion calculation of total phosphorus of Beijing Miyun Reservoir.Through calculated and compared the error of sedimentation rate by homotopy parametric inversion method and genetic inversion calculation method,the results indicate that homotopy parametric inversion method has good stability,calculating speed,and even if the initial selection away from the objective function,the solution still has a good convergence.展开更多
Nodal, a member of the transforming growth factor β （TGF-β） superfamily, has been shown to play a role in mesendoderm induction and gastrulation movements. The activity of Nodal signaling can be modulated by micro...Nodal, a member of the transforming growth factor β （TGF-β） superfamily, has been shown to play a role in mesendoderm induction and gastrulation movements. The activity of Nodal signaling can be modulated by microRNAs （miRNAs） as previously reported, but little is known about which miRNAs are regulated by Nodal during gastrulation. In the present study, we found that the expression of mir206, one of the most abundant miRNAs during zebrafish early embryo development, is regulated by Nodal signaling. Abrogation of Nodal signal activity results in defective convergence and extension （CE） movements, and these cell migration defects can be rescued by supplying an excess of mir206, suggesting that mir206 acts downstream of Nodal signaling to regulate CE movements. Furthermore, in mir206 morphants, the expression of cell adhesion molecule E-cadherin is significantly increased, while the key transcriptional repressor of E-cadherin, snailla, is depressed. Our study uncovers a novel mechanism by which Nodal-regulated mir206 modulates gastrulation movements in connection with the Snail/E-cadherin pathway.展开更多
文摘The posterior gut of the Drosophila embryo, consisting of hindgut and Malpighian tubules, provides a simple,well-defined system where it is possible to use a genetic approach to define components essential for epithelial morphogenesis.We review here the advantages of Drosophila as a model genetic organism, the morphogenesis of the epithelial structures of the posterior gut, and what is known about the genetic requirements to form these structures.In overview, primordia are patterned by expression of hierarchies of transcription factors; this leads to localized expression of cell signaling molecules, and finally, to the least understood step: modulation of cell adhesion and cell shape. We describe approaches to identify additional genes that are required for morphogenesis of these simple epithelia, particularly those that might play a structural role by affecting cell adhesion and cell shape.
文摘The large-scale convergence of homotopy parametric inversion method on the water quality model parameters calculated was used,with application in parametric inversion calculation of total phosphorus of Beijing Miyun Reservoir.Through calculated and compared the error of sedimentation rate by homotopy parametric inversion method and genetic inversion calculation method,the results indicate that homotopy parametric inversion method has good stability,calculating speed,and even if the initial selection away from the objective function,the solution still has a good convergence.
基金supported by the grants from the Major Science Programs of China(Nos.2011CBA01101 and 2011CB943904)the National Natural Science Foundation of China(Nos.30971656 and 90919011)
文摘Nodal, a member of the transforming growth factor β （TGF-β） superfamily, has been shown to play a role in mesendoderm induction and gastrulation movements. The activity of Nodal signaling can be modulated by microRNAs （miRNAs） as previously reported, but little is known about which miRNAs are regulated by Nodal during gastrulation. In the present study, we found that the expression of mir206, one of the most abundant miRNAs during zebrafish early embryo development, is regulated by Nodal signaling. Abrogation of Nodal signal activity results in defective convergence and extension （CE） movements, and these cell migration defects can be rescued by supplying an excess of mir206, suggesting that mir206 acts downstream of Nodal signaling to regulate CE movements. Furthermore, in mir206 morphants, the expression of cell adhesion molecule E-cadherin is significantly increased, while the key transcriptional repressor of E-cadherin, snailla, is depressed. Our study uncovers a novel mechanism by which Nodal-regulated mir206 modulates gastrulation movements in connection with the Snail/E-cadherin pathway.
