Specific domains of FoxD4/5 activate and repress neural transcription factor genes to control the progression of immature neural ectoderm to differentiating neural plate

Department of Anatomy and Regenerative Biology, George Washington University School of Medicine and Health Sciences, 2300 I Street NW, Washington DC, USA.
Developmental Biology (Impact Factor: 3.55). 03/2012; 365(2):363-75. DOI: 10.1016/j.ydbio.2012.03.004
Source: PubMed


FoxD4/5, a forkhead transcription factor, plays a critical role in establishing and maintaining the embryonic neural ectoderm. It both up-regulates genes that maintain a proliferative, immature neural ectoderm and down-regulates genes that promote the transition to a differentiating neural plate. We constructed deletion and mutant versions of FoxD4/5 to determine which domains are functionally responsible for these opposite activities, which regulate the critical developmental transition of neural precursors to neural progenitors to differentiating neural plate cells. Our results show that up-regulation of genes that maintain immature neural precursors (gem, zic2) requires the Acidic blob (AB) region in the N-terminal portion of the protein, indicating that the AB is the transactivating domain. Additionally, down-regulation of those genes that promote the transition to neural progenitors (sox) and those that lead to neural differentiation (zic, irx) involves: 1) an interaction with the Groucho co-repressor at the Eh-1 motif in the C-terminus; and 2) sequence downstream of this motif. Finally, the ability of FoxD4/5 to induce the ectopic expression of neural precursor genes in the ventral ectoderm also involves both the AB region and the Eh-1 motif; FoxD4/5 accomplishes ectopic neural induction by both activating neural precursor genes and repressing BMP signaling and epidermal genes. This study identifies the specific, conserved domains of the FoxD4/5 protein that allow this single transcription factor to regulate a network of genes that controls the transition of a proliferative neural ectodermal population to a committed neural plate population poised to begin differentiation.

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Available from: Sally A Moody, Oct 09, 2015
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    • "It directly activates a transcriptional triad consisting of Gmnn, Zic2 and Sox11, which in turn regulates the more down-stream components that promote the transition to neural stem and neural progenitor cells (Fig. 2). Finally, structure-function analyses of the Foxd4 protein show that it has separate domains in the Nand C-terminal regions that account for its ability to both activate or repress targets (Klein et al., 2013;Neilson et al., 2012). These findings illustrate how a single transcription factor can regulate the transition of immature, NE precursors to neurally-committed stem cells, and then to neural progenitors that are beginning to differentiate. "
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    Molecules and Cells 09/2014; 37(10). DOI:10.14348/molcells.2014.0227 · 2.09 Impact Factor
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    • "Numbers on each bar indicates sample size; * indicates significant difference from wild type (WT) at the p<0.001 level. Data for WT, ΔRII-Cterm and A6 are from [39]. "
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    ABSTRACT: FoxD4L1 is a forkhead transcription factor that expands the neural ectoderm by down-regulating genes that promote the onset of neural differentiation and up-regulating genes that maintain proliferative neural precursors in an immature state. We previously demonstrated that binding of Grg4 to an Eh-1 motif enhances the ability of FoxD4L1 to down-regulate target neural genes but does not account for all of its repressive activity. Herein we analyzed the protein sequence for additional interaction motifs and secondary structure. Eight conserved motifs were identified in the C-terminal region of fish and frog proteins. Extending the analysis to mammals identified a high scoring motif downstream of the Eh-1 domain that contains a tryptophan residue implicated in protein-protein interactions. In addition, secondary structure prediction programs predicted an α-helical structure overlapping with amphibian-specific Motif 6 in Xenopus, and similarly located α-helical structures in other vertebrate FoxD proteins. We tested functionality of this site by inducing a glutamine-to-proline substitution expected to break the predicted α-helical structure; this significantly reduced FoxD4L1's ability to repress zic3 and irx1. Because this mutation does not interfere with Grg4 binding, these results demonstrate that at least two regions, the Eh-1 motif and a more C-terminal predicted α-helical/Motif 6 site, additively contribute to repression. In the N-terminal region we previously identified a 14 amino acid motif that is required for the up-regulation of target genes. Secondary structure prediction programs predicted a short β-strand separating two acidic domains. Mutant constructs show that the β-strand itself is not required for transcriptional activation. Instead, activation depends upon a glycine residue that is predicted to provide sufficient flexibility to bring the two acidic domains into close proximity. These results identify conserved predicted motifs with secondary structures that enable FoxD4L1 to carry out its essential functions as both a transcriptional repressor and activator of neural genes.
    PLoS ONE 04/2013; 8(4):e61845. DOI:10.1371/journal.pone.0061845 · 3.23 Impact Factor
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    • "The GRN takes as a starting point early neural induction from which ANP specification evolves. As shown in Fig. 3, Sox3, Otx2, Ern1, Churchill and FoxD4/5 are among the first TFs to be expressed within the epiblast (Albazerchi and Stern, 2007; Neilson et al., 2012; Sheng et al., 2003; Streit et al., 2000; Yan et al., 2009). These genes, in combination with downstream effectors of the Wnt signalling pathway commit the ectoderm to a pre-neural state by inhibiting the expression of BMP4 and other ectodermal genes and by activating the neural determinants Sox2 and Sip1. "
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