Browsing by Author "Nakamura, Tetsuya"
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- Fluid flow and interlinked feedback loops establish left-right asymmetric decay of Cerl2 mRNAPublication . Nakamura, Tetsuya; Saito, Daisuke; Kawasumi, Aiko; Shinohara, Kyosuke; Asai, Yasuko; Takaoka, Katsuyoshi; Dong, Fenglan; Takamatsu, Atsuko; A. Belo, José; Mochizuki, Atsushi; Hamada, HiroshiBreaking of left-right symmetry in mouse embryos requires fluid flow at the node, but the precise action of the flow has remained unknown. Here we show that the left-right asymmetry of Cerl2 expression around the node, a target of the flow, is determined post-transcriptionally by decay of Cerl2 mRNA in a manner dependent on its 3' untranslated region. Cerl2 mRNA is absent specifically from the apical region of crown cells on the left side of the node. Preferential decay of Cerl2 mRNA on the left is initiated by the leftward flow and further enhanced by the operation of Wnt-Cerl2 interlinked feedback loops, in which Wnt3 upregulates Wnt3 expression and promotes Cerl2 mRNA decay, whereas Cerl2 promotes Wnt degradation. Mathematical modelling and experimental data suggest that these feedback loops behave as a bistable switch that can amplify in a noise-resistant manner a small bias conferred by fluid flow.
- Left-right asymmetry in the level of active Nodal protein produced in the node is translated into left-right asymmetry in the lateral plate of mouse embryosPublication . Kawasumi, Aiko; Nakamura, Tetsuya; Iwai, Naomi; Yashiro, Kenta; Saijoh, Yukio; Belo, Jose Antonio; Shiratori, Hidetaka; Hamada, HiroshiLeft-right (L-R) asymmetry in the mouse embryo is generated in the node and is dependent on cilia-driven fluid flow, but how the initial asymmetry is transmitted from the node to the lateral plate has remained unknown. We have now identified a transcriptional enhancer (ANE) in the human LEFTY1 gene that exhibits marked L>R asymmetric activity in perinodal cells of the mouse embryo. Dissection of ANE revealed that it is activated in the perinodal cells on the left side by Nodal signaling, suggesting that Nodal activity in the node is asymmetric at a time when Nodal expression is symmetric. Phosphorylated Smad2/3 (pSmad2) indeed manifested an L-R asymmetric distribution at the node, being detected in perinodal cells preferentially on the left side. This asymmetry in pSmad2 distribution was found to be generated not by unidirectional transport of Nodal but rather as a result of LR distribution of active Nodal in the node is translated into the asymmetry in LPM. (C) 2011 Elsevier Inc. All rights reserved.
- Mechanisms of left-right asymmetric signal generation around the nodePublication . Kawasumi, Aiko; Iwai, Naomi; Belo, José A.; Nakamura, Tetsuya; Shiratori, Hidetaka; Hamada, Hiroshi
- The dynamic right-to-left translocation of Cerl2 is involved in the regulation and termination of nodal activity in the mouse nodePublication . Inacio, Jose Manuel; Marques, Sara; Nakamura, Tetsuya; Shinohara, Kyosuke; Meno, Chikara; Hamada, Hiroshi; Belo, Jose AntonioThe determination of left-right body asymmetry in mouse embryos depends on the interplay of molecules In a highly sensitive structure, the node. Here, we show that the localization of Cerl2 protein does not correlate to its mRNA expression pattern, from 3-somite stage onwards. Instead, Cerl2 protein displays a nodal flow-dependent dynamic behavior that controls the activity of Nodal in the node, and the transmission of the laterality information to the left lateral plate mesoderm (LPM). Our results indicate that Cerl2 initially localizes and prevents the activation of Nodal genetic circuitry on the right side of the embryo, and later its right-to-left translocation shutdowns Nodal activity in the node. The consequent prolonged Nodal activity in the node by the absence of Cerl2 affects local Nodal expression and prolongs its expression in the LPM. Simultaneous genetic removal of both Nodal node inhibitors, Cerl2 and Lefty1, sustains even longer and bilateral his LPM expression.