Gdf11/Smad signalling and Cdx proteins cooperate to activate the Hoxc8 early enhancer in HepG2 cells

Abstract

Developing anatomy along the head-tail axis of bilaterian embryos is specified, to a large extent, by the overlapping patterns of expression of the Hox genes. Hox gene enhancers respond to a variety of signals in order to regulate these discreet domains of expression. For mouse Hoxc8, the 399bp "early enhancer" plays a major role. Activation of this enhancer is now examined using luciferase expression constructs transfected into HepG2 cells. Constructs are activated by the combined actions of Gdf11/Smad and Cdx protein signalling pathways, both of which are functional in early embryos. Each of these pathways alone has little stimulatory effect. Stimulation by the two pathways together exceeds the sum of the effects of each pathway alone, indicating synergistic activity. By mutation analysis, two Smad binding motifs are identified as mediators of the Gdf11 effect and two Cdx binding motifs mediate the Cdx effect. The two Smad motifs and one of the Cdx sites are conserved from fish to mammals. Gdf11 stimulation is partially inhibited by Specific Inhibitor of Smad3, suggesting that Smad3 plays a part in signal transduction. Fgf2 increases luciferase activation by the Hoxc8 enhancer, but not, apparently, by specific interactions with either Gdf11 or Cdx effects.

Role of Cdx factors in early mesodermal fate decisions

“…Although Cdx function has been shown to be crucial for numerous developmental programs, our understanding of the target genes governing these programs is incomplete. Cdx family members regulate target gene transcription through binding to a cognate response element (CDRE), of the consensus TTTATG, either in the proximity of their target genes (Suh et al, 1994;Subramanian et al, 1995) or at distal enhancer elements (Maier et al, 2005;Taylor et al, 1997;Gaunt, 2017). Although Cdx family members typically positively regulate transcription, there is a growing body of evidence that suggests they can also act as transcriptional repressors.…”

GDF11 Modulates Ca2+-Dependent Smad2/3 Signaling to Prevent Cardiomyocyte Hypertrophy

“…TGF-β-like proteins, such as GDF11, recruit and induce the phosphorylation of receptor-regulated Smad (from Drosophila homolog “mothers against decapentaplegic”, and the smooth muscle actin protein in Caenorhabditis elegans ). Smad2 and Smad3 (Smad2/3) transduce extracellular signals from activin/TGF-β receptor ligands [ 16 , 17 ]. Smad2/3 proteins possess two globular domains associated by a linker region.…”

Bioinformatics Network Analyses of Growth Differentiation Factor 11 Anti-aging Study

“…The later give us a new research direction of GDF11 involved in apoptosis. The classical pathway of GDF11 is through SMADs which acts by regulating diverse biological effects by partnering with various transcription factors 20 . MYC inhibitor CTCF is one of the GDF11/SMADs downstream transcription factor 11 and also appearing in our GDF11 transcription network with MYC.…”