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Antagonism between Smad1 and Smad2 signaling determines the site of distal visceral endoderm formation in the mouse embryo.

Yamamoto M, Beppu H, Takaoka K, Meno C, Li E, Miyazono K, Hamada H - J. Cell Biol. (2009)

Bottom Line: A Smad2-activating factor such as Activin also contributes to DVE formation by generating a region of VE positive for the Smad2 signal and negative for Smad1 signal.DVE is thus formed at the distal end of the embryo, the only region of VE negative for the Smad1 signal and positive for Smad2 signal.An inverse relation between the level of phosphorylated Smad1 and that of phosphorylated Smad2 in VE suggests an involvement of antagonism between Smad1- and Smad2-mediated signaling.

View Article: PubMed Central - PubMed

Affiliation: Developmental Genetics Group, Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan. myamamoto@fbs.osaka-u.ac.jp

ABSTRACT
The anterior-posterior axis of the mouse embryo is established by formation of distal visceral endoderm (DVE) and its subsequent migration. The precise mechanism of DVE formation has remained unknown, however. Here we show that bone morphogenetic protein (BMP) signaling plays dual roles in DVE formation. BMP signaling is required at an early stage for differentiation of the primitive endoderm into the embryonic visceral endoderm (VE), whereas it inhibits DVE formation, restricting it to the distal region, at a later stage. A Smad2-activating factor such as Activin also contributes to DVE formation by generating a region of VE positive for the Smad2 signal and negative for Smad1 signal. DVE is thus formed at the distal end of the embryo, the only region of VE negative for the Smad1 signal and positive for Smad2 signal. An inverse relation between the level of phosphorylated Smad1 and that of phosphorylated Smad2 in VE suggests an involvement of antagonism between Smad1- and Smad2-mediated signaling.

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p-Smad1 in wild-type and Bmpr2−/− embryos. Wild-type (A–C) or Bmpr2−/− (A'–C') embryos at the indicated stages of development were subjected to immunohistofluorescence staining with antibodies to p-Smad1 (pS1; green); merged images with staining of nuclei by YOYO-1 (Nuc; red) are also shown. Staining for p-Smad1 was decreased in Bmpr2−/− embryos. Bars, 50 µm.
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fig2: p-Smad1 in wild-type and Bmpr2−/− embryos. Wild-type (A–C) or Bmpr2−/− (A'–C') embryos at the indicated stages of development were subjected to immunohistofluorescence staining with antibodies to p-Smad1 (pS1; green); merged images with staining of nuclei by YOYO-1 (Nuc; red) are also shown. Staining for p-Smad1 was decreased in Bmpr2−/− embryos. Bars, 50 µm.

Mentions: To evaluate how the lack of BMPR2 affects BMP signaling in the embryo, we examined the distribution of phosphorylated Smad1/5 (p-Smad1) in Bmpr2−/− embryos by immunohistofluorescence staining. In wild-type embryos, p-Smad1 was found in the nuclei of epiblast and primitive endoderm cells at E4.5 and of epiblast and VE cells at E5.2 (Fig. 1 N and Fig. 2, A and B). The distribution of p-Smad1 changed quickly between E5.2 and E5.5 and had shifted to the proximal epiblast and VE, excluding DVE, at E5.5 (Fig. 2 C and Fig. S3, A–J, available at http://www.jcb.org/cgi/content/full/jcb.200808044/DC1). In Bmpr2−/− embryos, the distribution of p-Smad1 was similar to that in wild-type embryos at E4.5 but showed two distinct patterns at later stages (Fig. 1 N and Fig. 2, A'–C'). In severely affected mutant embryos (8/14 embryos at E5.2 and 8/15 embryos at E5.5), p-Smad1 was apparent only in the proximal VE at E5.2 (8/8 embryos; Fig. 2 B') and was barely detected at E5.5 (8/8 embryos; Fig. 2 C'). In mildly affected embryos (6/14 embryos at E5.5 and 7/15 embryos at E5.5), p-Smad1 was found in the same regions as in wild-type embryos at E5.2, but its abundance was lower than that in the wild type (6/6 embryos; Fig. 1 N and Fig. S2). It was not detected in the epiblast and there were fewer positive cells in the VE of the mildly affected embryos at E5.5 (7/7 embryos; Fig. S2). These data suggested that BMP signaling is not completely lost but is reduced in Bmpr2−/− embryos. Other type 2 receptors may thus play a redundant role in this mutant. Variability in the phenotype of Bmpr2−/− embryos is most likely caused by the variable level of BMP signaling that remains.


Antagonism between Smad1 and Smad2 signaling determines the site of distal visceral endoderm formation in the mouse embryo.

Yamamoto M, Beppu H, Takaoka K, Meno C, Li E, Miyazono K, Hamada H - J. Cell Biol. (2009)

p-Smad1 in wild-type and Bmpr2−/− embryos. Wild-type (A–C) or Bmpr2−/− (A'–C') embryos at the indicated stages of development were subjected to immunohistofluorescence staining with antibodies to p-Smad1 (pS1; green); merged images with staining of nuclei by YOYO-1 (Nuc; red) are also shown. Staining for p-Smad1 was decreased in Bmpr2−/− embryos. Bars, 50 µm.
© Copyright Policy - openaccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2654303&req=5

fig2: p-Smad1 in wild-type and Bmpr2−/− embryos. Wild-type (A–C) or Bmpr2−/− (A'–C') embryos at the indicated stages of development were subjected to immunohistofluorescence staining with antibodies to p-Smad1 (pS1; green); merged images with staining of nuclei by YOYO-1 (Nuc; red) are also shown. Staining for p-Smad1 was decreased in Bmpr2−/− embryos. Bars, 50 µm.
Mentions: To evaluate how the lack of BMPR2 affects BMP signaling in the embryo, we examined the distribution of phosphorylated Smad1/5 (p-Smad1) in Bmpr2−/− embryos by immunohistofluorescence staining. In wild-type embryos, p-Smad1 was found in the nuclei of epiblast and primitive endoderm cells at E4.5 and of epiblast and VE cells at E5.2 (Fig. 1 N and Fig. 2, A and B). The distribution of p-Smad1 changed quickly between E5.2 and E5.5 and had shifted to the proximal epiblast and VE, excluding DVE, at E5.5 (Fig. 2 C and Fig. S3, A–J, available at http://www.jcb.org/cgi/content/full/jcb.200808044/DC1). In Bmpr2−/− embryos, the distribution of p-Smad1 was similar to that in wild-type embryos at E4.5 but showed two distinct patterns at later stages (Fig. 1 N and Fig. 2, A'–C'). In severely affected mutant embryos (8/14 embryos at E5.2 and 8/15 embryos at E5.5), p-Smad1 was apparent only in the proximal VE at E5.2 (8/8 embryos; Fig. 2 B') and was barely detected at E5.5 (8/8 embryos; Fig. 2 C'). In mildly affected embryos (6/14 embryos at E5.5 and 7/15 embryos at E5.5), p-Smad1 was found in the same regions as in wild-type embryos at E5.2, but its abundance was lower than that in the wild type (6/6 embryos; Fig. 1 N and Fig. S2). It was not detected in the epiblast and there were fewer positive cells in the VE of the mildly affected embryos at E5.5 (7/7 embryos; Fig. S2). These data suggested that BMP signaling is not completely lost but is reduced in Bmpr2−/− embryos. Other type 2 receptors may thus play a redundant role in this mutant. Variability in the phenotype of Bmpr2−/− embryos is most likely caused by the variable level of BMP signaling that remains.

Bottom Line: A Smad2-activating factor such as Activin also contributes to DVE formation by generating a region of VE positive for the Smad2 signal and negative for Smad1 signal.DVE is thus formed at the distal end of the embryo, the only region of VE negative for the Smad1 signal and positive for Smad2 signal.An inverse relation between the level of phosphorylated Smad1 and that of phosphorylated Smad2 in VE suggests an involvement of antagonism between Smad1- and Smad2-mediated signaling.

View Article: PubMed Central - PubMed

Affiliation: Developmental Genetics Group, Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan. myamamoto@fbs.osaka-u.ac.jp

ABSTRACT
The anterior-posterior axis of the mouse embryo is established by formation of distal visceral endoderm (DVE) and its subsequent migration. The precise mechanism of DVE formation has remained unknown, however. Here we show that bone morphogenetic protein (BMP) signaling plays dual roles in DVE formation. BMP signaling is required at an early stage for differentiation of the primitive endoderm into the embryonic visceral endoderm (VE), whereas it inhibits DVE formation, restricting it to the distal region, at a later stage. A Smad2-activating factor such as Activin also contributes to DVE formation by generating a region of VE positive for the Smad2 signal and negative for Smad1 signal. DVE is thus formed at the distal end of the embryo, the only region of VE negative for the Smad1 signal and positive for Smad2 signal. An inverse relation between the level of phosphorylated Smad1 and that of phosphorylated Smad2 in VE suggests an involvement of antagonism between Smad1- and Smad2-mediated signaling.

Show MeSH