Bmp Indicator Mice Reveal Dynamic Regulation of Transcriptional Response

Anna L Javier,N Soledad Reyes De Mochel,Mui Luong,Linda T Doan,Aixu Sun,Ken W Y Cho,Edwin S Monuki,Michael Schubert

doi:10.1371/journal.pone.0042566

Anna L Javier, N Soledad Reyes De Mochel + Show 6 more

Open Access

https://doi.org/10.1371/journal.pone.0042566

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Journal: PloS one	Publication Date: Sep 11, 2012
Citations: 33	License type: CC BY 4.0

Affiliation: University of California, Irvine

Abstract

Cellular responses to Bmp ligands are regulated at multiple levels, both extracellularly and intracellularly. Therefore, the presence of these growth factors is not an accurate indicator of Bmp signaling activity. While a common approach to detect Bmp signaling activity is to determine the presence of phosphorylated forms of Smad1, 5 and 8 by immunostaining, this approach is time consuming and not quantitative. In order to provide a simpler readout system to examine the presence of Bmp signaling in developing animals, we developed BRE-gal mouse embryonic stem cells and a transgenic mouse line that specifically respond to Bmp ligand stimulation. Our reporter identifies specific transcriptional responses that are mediated by Smad1 and Smad4 with the Schnurri transcription factor complex binding to a conserved Bmp-Responsive Element (BRE), originally identified among Drosophila, Xenopus and human Bmp targets. Our BRE-gal mES cells specifically respond to Bmp ligands at concentrations as low as 5 ng/ml; and BRE-gal reporter mice, derived from the BRE-gal mES cells, show dynamic activity in many cellular sites, including extraembryonic structures and mammary glands, thereby making this a useful scientific tool.

Highlights

Bmp ligands are secreted growth factors that trigger activation of a highly conserved signaling circuit that is utilized throughout development, from the subdivision of tissue types during early embryogenesis to the formation of limbs and internal organs
We developed a simple readout system to examine the presence of Bmp signaling in both mouse embryonic stem cells, and a transgenic mouse line, that detects the transcriptional output mediated by a Bmp response element (BRE) we characterized previously [10,11]
We tested whether the same Xenopus BRE responds to Bmp signaling in mouse embryonic stem (mES) cells

Summary

Introduction

Bmp ligands are secreted growth factors that trigger activation of a highly conserved signaling circuit that is utilized throughout development, from the subdivision of tissue types during early embryogenesis to the formation of limbs and internal organs. Regulation of Bmp signaling activity is very dynamic and complicated, involving multiple layers of regulation both at the extracellular and intracellular levels Extracellular modulators such as Chordin and Noggin are often expressed by the same or nearby cells to antagonize the Bmp signal [1,2,3,4]. A common approach used to detect the spatial localization of Bmp activity is to perform immunostaining on embryos or tissues with antibodies that recognize the phosphorylated forms of Smad and 8 (P-Smad1/5/8). This approach can be tedious and time consuming, and has the drawback of not sensing the transcriptional response of a cell. We developed a simple readout system to examine the presence of Bmp signaling in both mouse embryonic stem (mES) cells, and a transgenic mouse line, that detects the transcriptional output mediated by a Bmp response element (BRE) we characterized previously [10,11]

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