Foxf2 is required for secondary palate development and Tgfβ signaling in palatal shelf mesenchyme

Abstract

The secondary palate separates the oral from the nasal cavity and its closure during embryonic development is sensitive to genetic perturbations. Mice with deleted Foxf2, encoding a forkhead transcription factor, are born with cleft palate, and an abnormal tongue morphology has been proposed as the underlying cause. Here, we show that Foxf2(-/-) maxillary explants cultured in vitro, in the absence of tongue and mandible, failed to close the secondary palate. Proliferation and collagen content were decreased in Foxf2(-/-) palatal shelf mesenchyme. Phosphorylation of Smad2/3 was reduced in mutant palatal shelf, diagnostic of attenuated canonical Tgfβ signaling, whereas phosphorylation of p38 was increased. The amount of Tgfβ2 protein was diminished, whereas the Tgfb2 mRNA level was unaltered. Expression of several genes encoding extracellular proteins important for Tgfβ signaling were reduced in Foxf2(-)(/)(-) palatal shelves: a fibronectin splice-isoform essential for formation of extracellular Tgfβ latency complexes; Tgfbr3 - or betaglycan - which acts as a co-receptor and an extracellular reservoir of Tgfβ; and integrins αV and β1, which are both Tgfβ targets and required for activation of latent Tgfβ. Decreased proliferation and reduced extracellular matrix content are consistent with diminished Tgfβ signaling. We therefore propose that gene expression changes in palatal shelf mesenchyme that lead to reduced Tgfβ signaling contribute to cleft palate in Foxf2(-)(/)(-) mice.

Sonic Hedgehog regulation of Foxf2 promotes cranial neural crest mesenchyme proliferation and is disrupted in cleft lip morphogenesis

“…This results in loss of Shh expression in the palatal shelf epithelium and in CPO (Xu et al, 2016). Suggesting a likely parallel mechanism, Nik et al (2016) found that Foxf2 expression regulates TGFβ signaling activity in the cNCC-derived mesenchyme of the secondary palate. Disruption of TGFβ signaling in these cells has been shown to cause defective proliferation, resulting in cleft palate (Iwata et al, 2012).…”

“…While Foxf2 has an intrinsic role in secondary palate development, its role in upper lip development and cleft lip pathogenesis had not been described (Wang et al, 2003;Xu et al, 2016;Nik et al, 2016). We therefore further examined the expression of Foxf2 during upper lip morphogenesis in our mouse model.…”

Transcriptomic analysis of bone and fibrous tissue morphogenesis during digit tip regeneration in the adult mouse

“…TFs of note include Hox genes, which direct distal limb (Hoxa11/Hoxd11) and digit development (Hoxa13/Hoxd13) (Fromental-Ramain et al, 1996;Villavicencio-Lorini et al, 2010;Zakany and Duboule, 1999); Prrx1, which is required for early skeletogenesis and modulates limb segment length (Cretekos et al, 2008;ten Berge et al, 1998); Alx4 and Tbx2, which affect limb patterning (Kuijper et al, 2005;Sheeba and Logan, 2017); and Runx2, which is a master regulator of osteoblast differentiation (Komori, 2010). Other transiently upregulated TFs in Regen digits include those involved in ECM organization (Foxf2) (Nik et al, 2016), ossification (Runx3) (Bauer et al, 2015), and angiogenesis (Sox17) (Corada et al, 2013). One downregulated TF linked to positive regulation of cell proliferation, Hmga2, is associated with stem cell self-renewal (Hammond and Sharpless, 2008) and tumorigenesis in various tissues (Pallante et al, 2015).…”

Extracellular Matrix Remodeling During Palate Development

“…[9][10][11][12][13][14] Multiple signaling pathways important for palatogenesis such as FGF, TGF β, BMP, and SHH regulate ECM dynamics during palate development ( Figure 1). [6][7][8][14][15][16][17][18] In this review, we will summarize the dynamic deposition and degradation of ECM during palate development.…”