Dkk1‐dependent inhibition of Wnt signaling activates Hesx1 expression through its 5′ enhancer and directs forebrain precursor development

Abstract

Development of the anterior forebrain precursor (AFBP) in the anterior neural plate (ANP) depends on the activation of the Hesx1 transcription factor gene. The Hesx1-expression domain of the ANP is underlain by Dkk1-expressing tissues, initially proximal-most anterior visceral endoderm (AVE), and later anterior mesendoderm (AME). As Dkk1-null embryos fail to develop the Hesx1-expressing domain, it is likely that Wnt signal inhibition in the ANP is required for the Hesx1 activation. To investigate the regulation of the AFBP development, we took advantage of epiblast stem cells (EpiSCs), which develop into the ANP in the absence of activin signaling. Expression of Hesx1 and Six3, both involved in the AFBP development, was strongly activated 2 days after activin removal and concomitant addition of Wnt signal inhibitors, Dkk1 or XAV939. Furthermore, we showed that activation of the 720-bp Hesx1 5′ enhancer is responsible for Hesx1 expression in the AFBP and depends on Wnt signal inhibition. In addition, we showed that Wnt inhibition during the first day has larger impact on the activation of Hesx1 and Six3 than the second day, suggesting that in embryos Wnt inhibition caused by the AVE-derived Dkk1, rather than the AME-derived Dkk1, contributes greatly in the establishment of the AFBP.

Müller glia reactivity follows retinal injury despite the absence of the glial fibrillary acidic protein gene in Xenopus

“…5K). Similar to prph , ina expression was also observed in the DRG (not shown, and Matsuda and Kondoh, 2014). ina expression was also detected in the lateral brain (Fig.…”

“…Retinal expression of ina at stage 50 is restricted to the ganglion cell layer (Fig. 5J and Matsuda and Kondoh, 2014). Expression was also observed in a few cells dispersed in the inner nuclear layer, possibly Müller gila, amacrine or displaced ganglion cells (Fig.…”

“…In situ hybridization on tissue sections was performed as previously described (Hemmati-Brivanlou et al, 1992; Matsuda and Kondoh, 2014; Viczian et al, 2006). …”

ChIP-seq analysis of genomic binding regions of five major transcription factors in mouse epiblast stem cells that highlights a central role for ZIC2

“…The success in establishing epiblast stem cells (EpiSCs) from the epiblasts of egg-cylinder-stage mouse embryos (Brons et al, 2007; Tesar et al, 2007; Sumi et al, 2013) created new opportunities for investigating the gene regulatory networks in the epiblast and for deriving specific somatic cell lineages (Iwafuchi-Doi et al, 2011, 2012; Acampora et al, 2013; Factor et al, 2014; Kojima et al, 2014; Matsuda and Kondoh, 2014; Tsakiridis et al, 2014; Henrique et al, 2015; Li et al, 2015; Song et al, 2016). EpiSCs can be maintained in feeder-free culture conditions supplemented with activin, which is a Nodal replacement, and bFGF (FGF2) (Brons et al, 2007; Iwafuchi-Doi et al, 2012).…”

“…EpiSCs can be maintained in feeder-free culture conditions supplemented with activin, which is a Nodal replacement, and bFGF (FGF2) (Brons et al, 2007; Iwafuchi-Doi et al, 2012). They can also be directed towards development into a variety of specific somatic lineages by removing activin and/or manipulating other cell signaling systems (Brons et al, 2007; Tesar et al, 2007; Iwafuchi-Doi et al, 2012; Kojima et al, 2014; Matsuda and Kondoh, 2014; Tsakiridis et al, 2014; Li et al, 2015). For example, simple removal of activin/Nodal signaling directs EpiSCs to develop into anterior neural plate (ANP) cells (Iwafuchi-Doi et al, 2012).…”