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Development 2019 May 22;14610:. doi: 10.1242/dev.173112.
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Barhl2 maintains T cell factors as repressors and thereby switches off the Wnt/β-Catenin response driving Spemann organizer formation.

Sena E , Rocques N , Borday C , Muhamad Amin HS , Parain K , Sitbon D , Chesneau A , Durand BC .

A hallmark of Wnt/β-Catenin signaling is the extreme diversity of its transcriptional response, which varies depending on the cell and developmental context. What controls this diversity is poorly understood. In all cases, the switch from transcriptional repression to activation depends on a nuclear increase in β-Catenin, which detaches the transcription factor T cell factor 7 like 1 (Tcf7l1) bound to Groucho (Gro) transcriptional co-repressors from its DNA-binding sites and transiently converts Tcf7/Lymphoid enhancer binding factor 1 (Lef1) into a transcriptional activator. One of the earliest and evolutionarily conserved functions of Wnt/β-Catenin signaling is the induction of the blastopore lip organizer. Here, we demonstrate that the evolutionarily conserved BarH-like homeobox-2 (Barhl2) protein stabilizes the Tcf7l1-Gro complex and maintains the repressed expression of Tcf target genes by a mechanism that depends on histone deacetylase 1 (Hdac-1) activity. In this way, Barhl2 switches off the Wnt/β-Catenin-dependent early transcriptional response, thereby limiting the formation of the organizer in time and/or space. This study reveals a novel nuclear inhibitory mechanism of Wnt/Tcf signaling that switches off organizer fate determination.

PubMed ID: 31036545
Article link: Development

Species referenced: Xenopus laevis
Genes referenced: acvr1 adm barhl2 ccnd1 chrd ctnnb1 foxb1 gsc hdac1 myc nusap1 otx2 psmd6 shh sia1 sox3 tcf7 tcf7l1 tle4 ventx2.2 wnt8a wnt8b
GO keywords: cell fate determination
Morpholinos: barhl2 MO1 barhl2 MO2

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