Differential binding of Lef1 and Msx1/2 transcription factors to Dkk1 CNEs correlates with reporter gene expression in vivo

TY - JOUR

T1 - Differential binding of Lef1 and Msx1/2 transcription factors to Dkk1 CNEs correlates with reporter gene expression in vivo

AU - Dr Lieven, Oliver Wilm

AU - Dronka, Julia

AU - Burmühl, Stephan

AU - Rüther, Ulrich

PY - 2014/12/29

Y1 - 2014/12/29

N2 - Besides the active Wnt signalling itself, the extracellular inhibition by Dkk1 is important for various embryonic developmental processes, such as optic vesicle differentiation and facial outgrowth. Although a feedback crosstalk of the active Wnt/b-catenin signaling and Dkk1 regulation has been suggested, the control of Dkk1 transcription by the Tcf/Lef1 mediated Wnt signalling and its connection to additional signalling factors has not been elucidated in vivo. Here, we used a combination of transgenic mouse approaches and biochemical analyses to unravel the direct Dkk1 transcriptional regulation via Tcf/Lefs. By using site directed mutagenesis, we tested several conserved Tcf/Lef1 binding sites within Dkk1 conserved non-coding elements (CNEs) and found that these are required for tissue specific reporter expression. In addition a conserved Msx1/2 binding site is required for retinal reporter expression and Msx2 but not Msx1 binds its conserved binding site within CNE195 in the optic cups. Within craniofacial expression domains, Lef1 interferes with Dkk1 directly via two conserved Tcf/Lef1 binding sites in the craniofacial enhancer CNE114, both of which are required for the general craniofacial Dkk1 reporter activation. Furthermore, these Tcf/Lef1 sites are commonly bound in the whisker hair bud mesenchyme but specifically Tcf/Lef1 (no. 2) is required for mandibular activation and repression of maxillar Dkk1 activation. Lastly, we tested the Tcf/Lef1 binding capacities of the Dkk1 promoter and found that although Lef1 binds the Dkk1 promoter, these sites are not sufficient for tissue specific Dkk1 activation. Together, we here present the importance of conserved Tcf/Lef1 and Msx1/2 sites that are required for differential Dkk1 transcriptional reporter activation in vivo. This requirement directly correlates with Lef1 and Msx1/2 interaction with these genomic loci.

AB - Besides the active Wnt signalling itself, the extracellular inhibition by Dkk1 is important for various embryonic developmental processes, such as optic vesicle differentiation and facial outgrowth. Although a feedback crosstalk of the active Wnt/b-catenin signaling and Dkk1 regulation has been suggested, the control of Dkk1 transcription by the Tcf/Lef1 mediated Wnt signalling and its connection to additional signalling factors has not been elucidated in vivo. Here, we used a combination of transgenic mouse approaches and biochemical analyses to unravel the direct Dkk1 transcriptional regulation via Tcf/Lefs. By using site directed mutagenesis, we tested several conserved Tcf/Lef1 binding sites within Dkk1 conserved non-coding elements (CNEs) and found that these are required for tissue specific reporter expression. In addition a conserved Msx1/2 binding site is required for retinal reporter expression and Msx2 but not Msx1 binds its conserved binding site within CNE195 in the optic cups. Within craniofacial expression domains, Lef1 interferes with Dkk1 directly via two conserved Tcf/Lef1 binding sites in the craniofacial enhancer CNE114, both of which are required for the general craniofacial Dkk1 reporter activation. Furthermore, these Tcf/Lef1 sites are commonly bound in the whisker hair bud mesenchyme but specifically Tcf/Lef1 (no. 2) is required for mandibular activation and repression of maxillar Dkk1 activation. Lastly, we tested the Tcf/Lef1 binding capacities of the Dkk1 promoter and found that although Lef1 binds the Dkk1 promoter, these sites are not sufficient for tissue specific Dkk1 activation. Together, we here present the importance of conserved Tcf/Lef1 and Msx1/2 sites that are required for differential Dkk1 transcriptional reporter activation in vivo. This requirement directly correlates with Lef1 and Msx1/2 interaction with these genomic loci.

KW - Animals

KW - Binding Sites

KW - Enhancer Elements, Genetic

KW - Gene Expression Regulation, Developmental

KW - Genes, Reporter

KW - Homeodomain Proteins

KW - Intercellular Signaling Peptides and Proteins

KW - Lymphoid Enhancer-Binding Factor 1

KW - MSX1 Transcription Factor

KW - Mesoderm

KW - Mice

KW - Organ Specificity

KW - Protein Binding

KW - Transcriptional Activation

U2 - 10.1371/journal.pone.0115442

DO - 10.1371/journal.pone.0115442

M3 - Journal article

C2 - 25545010

SN - 1932-6203

SP - 1

EP - 23

JO - PLOS ONE

JF - PLOS ONE

M1 - e115442

ER -