Wnt/β-catenin signaling regulates the expression of the homeobox gene Cdx1 in embryonic intestine

Abstract

During mammalian development, the Cdx1 homeobox gene exhibits an early period of expression when the embryonic body axis is established, and a later period where expression is restricted to the embryonic intestinal endoderm. Cdx1 expression is maintained throughout adulthood in the proliferative cell compartment of the continuously renewed intestinal epithelium, the crypts. In this study, we provide evidence in vitro and in vivo that Cdx1 is a direct transcriptional target of the Wnt/(beta)-catenin signaling pathway. Upon Wnt stimulation, expression of Cdx1 can be induced in mouse embryonic stem (ES) cells as well as in undifferentiated rat embryonic endoderm. Tcf4-deficient mouse embryos show abrogation of Cdx1 protein in the small intestinal epithelium, making Tcf4 the likely candidate to transduce Wnt signal in this part of gut. The promoter region of the Cdx1 gene contains several Tcf-binding motifs, and these bind Tcf/Lef1/(beta)-catenin complexes and mediate (beta)-catenin-dependent transactivation. The transcriptional regulation of the homeobox gene Cdx1 in the intestinal epithelium by Wnt/(beta)-catenin signaling underlines the importance of this signaling pathway in mammalian endoderm development.

Transcription of microRNAs is regulated by developmental signaling pathways and transcription factors

“…ATAC-seq reads were found overlapping the predicted binding sites for Klf15 and SNAI1 upstream of this Sp miR-1 locus at multiple timepoints between 24 and 60 hpf, indicating that the sites are maintained as open euchromatin during early development ( Buenrostro et al, 2013 ; Buenrostro et al, 2015 ; Shashikant and Ettensohn, 2019 ; Arshinoff et al, 2022 ; Telmer et al, 2024 ). Further upstream, we identified potential binding sites for HMG protein Tcf/Lef (566bp upstream), and caudal type homeobox 1-like, all of which are also regulated by Wnt signaling (Tcf/Lef and caudal are upregulated by cWnt) ( Novak and Dedhar, 1999 ; Lickert et al, 2000 ; Noack et al, 2019 ). Lv miR-1 (within 150 bp) did not yield any predicted binding sites for the same factors identified in the purple sea urchin at similar distances from Sp miR-1 ( Table 1 , Supplementary Table S3 ).…”

“…The level of Sp miR-2012 was found to be significantly decreased by disruption of cWnt, ncWnt/PCP (ROCK), Nodal, and MAPK signaling pathways ( Figure 1B ; Figure 2 ). Predicted binding sites for Wnt-regulated TFs were identified, including caudal type homeobox 1-like (upregulated by cWnt), hepatocyte nuclear factor 4 alpha (downregulated by cWnt), and HMG protein Tcf/Lef (downregulated by cWnt) ( Table 1 ; Figure 4F ) ( Novak and Dedhar, 1999 ; Lickert et al, 2000 ; Yang et al, 2013 ; Noack et al, 2019 ). Sites for caudal type homeobox 1-like, hepatocyte nuclear factor 4 alpha, and HMG protein Tcf/Lef overlapped with ATAC-seq reads between 18 and 70 hpf.…”