Ectodermal Organ Development Is Regulated by a microRNA-26b-Lef-1-Wnt Signaling Axis

Abstract

The developmental role of Lef-1 in ectodermal organs has been characterized using Lef-1 murine knockout models. We generated a Lef-1 conditional over-expression (COEL) mouse to determine the role of Lef-1 expression in epithelial structures at later stages of development after endogenous expression switches to the mesenchyme. Lef-1 over expression (OE) in the oral epithelium creates a new dental epithelial stem cell niche that significantly increases incisor growth. These data indicate that Lef-1 expression is switched off in the dental epithelial at early stages to maintain the stem cell niche and regulate incisor growth. Bioinformatics analyses indicated that miR-26b expression increased coinciding with decreased Lef-1 expression in the dental epithelium. We generated a murine model over-expressing miR-26b that targets endogenous Lef-1 expression and Lef-1-related developmental mechanisms. miR-26b OE mice have ectodermal organ defects including a lack of incisors, molars, and hair similar to the Lef-1 null mice. miR-26b OE rescues the Lef-1 OE phenotype demonstrating a critical genetic and developmental role for miR-26b in the temporal and spatial expression of Lef-1 in epithelial tissues. Lef-1 expression regulates Wnt signaling and Wnt target genes as well as cell proliferation mechanisms, while miR-26b OE reduced the levels of Wnt target gene expression. The extra stem cell compartment in the COEL mice expressed Lef-1 suggesting that Lef-1 is a stem cell factor, which was absent in the miR-26b OE/COEL rescue mice. This is the first demonstration of a microRNA OE mouse model that has ectodermal organ defects. These findings demonstrate that the levels of Lef-1 are critical for development and establish a role for miR-26b in the regulation of ectodermal organ development through the control of Lef-1 expression and an endogenous stem cell niche.

miR-17 acts as a tumor suppressor by negatively regulating the miR-17-92 cluster

“…The PMIS system can be used to specifically inhibit target miR function through seed sequence recognition. 20 , 21 , 22 , 23 In order to inhibit the different miRs in the miR-17-92 cluster, different PMIS constructs were designed to target the seed region of miR-17 , miR-18a , miR-19a , and miR-92a-1 , and stable cell lines were created by infecting SW579 with PMIS lentivirus constructs expressing GFP. As a control, we used the SW579 cell line expressing a PMIS empty vector, which does not inhibit miR function.…”

HMGN2 represses gene transcription via interaction with transcription factors Lef-1 and Pitx2 during amelogenesis

“…We next determined if dental epithelial cell proliferation was affected in the lower incisor of Hmgn2 −/− embryos. We have previously shown that Pitx2 and Lef-1 control dental epithelial cell proliferation and differentiation ( 24 , 25 , 49 ). Our hypothesis is that the loss of Hmgn2 would increase the transcriptional activity of factors involved in dental epithelial cell proliferation and differentiation.…”

FOXP4 promotes laryngeal squamous cell carcinoma progression through directly targeting LEF‑1

“…The results demonstrated that FOXP4 positively regulated the expression levels of G1/S-specific cyclin-D1 (CCND1), JUN, MYC and MMP7 ( Fig. 4H ), which are well-established downstream target genes of the Wnt pathway ( 18 ). Collectively, these data suggested that FOXP4 activates the Wnt signaling pathway.…”

“…The current study verified that FOXP4 directly targeted the LEF-1 promoter and regulated its transcriptional activity, as confirmed via ChIP and luciferase reporter assays. LEF-1 is a member of the LEF/TCF transcription factor family and is a well-known binding partner of β-catenin, which promotes the activation of Wnt signaling ( 18 ). Whether FOXP4 exerted its carcinogenic effect via regulating Wnt signaling was further examined in the present study by measuring the expression levels of the Wnt/β-catenin signaling-related target genes.…”