Sox2 Controls Periderm and Rugae Development to Inhibit Oral Adhesions

Abstract

In humans, ankyloglossia and cleft palate are common congenital craniofacial anomalies, and these are regulated by a complex gene regulatory network. Understanding the genetic underpinnings of ankyloglossia and cleft palate will be an important step toward rational treatment of these complex anomalies. We inactivated the Sry (sex-determining region Y)–box 2 ( Sox2) gene in the developing oral epithelium, including the periderm, a transient structure that prevents abnormal oral adhesions during development. This resulted in ankyloglossia and cleft palate with 100% penetrance in embryos examined after embryonic day 14.5. In Sox2 conditional knockout embryos, the oral epithelium failed to differentiate, as demonstrated by the lack of keratin 6, a marker of the periderm. Further examination revealed that the adhesion of the tongue and mandible expressed the epithelial markers E-Cad and P63. The expanded epithelia are Sox9-, Pitx2-, and Tbx1-positive cells, which are markers of the dental epithelium; thus, the dental epithelium contributes to the development of oral adhesions. Furthermore, we found that Sox2 is required for palatal shelf extension, as well as for the formation of palatal rugae, which are signaling centers that regulate palatogenesis. In conclusion, the deletion of Sox2 in oral epithelium disrupts palatal shelf extension, palatal rugae formation, tooth development, and periderm formation. The periderm is required to inhibit oral adhesions and ankyloglossia, which is regulated by Sox2. In addition, oral adhesions occur through an expanded dental epithelial layer that inhibits epithelial invagination and incisor development. This process may contribute to dental anomalies due to ankyloglossia.

Identification of novel susceptibility loci for non‐syndromic cleft lip with or without cleft palate

“…Injecting p53 −/− embryos with sertad4 MO generated the same morphological abnormalities, indicating that the deformities observed in morphants are not caused by up‐regulation of the p53‐dependent apoptotic pathway 26 (Figure A). Further, since Sox2 regulates development of the palate rugae, and a loss of this palate signalling centre may contribute to clefting 27 . Thus, we investigated the expression of sox2 and found it was significantly down‐regulated in sertad4 knockdown zebrafish models at 96hpf (Figure B).…”

“…29 The sertad4 knockdown in our zebrafish model induced mandibular deficiency, heart failure and down-regulation of Sox2 protein which had been implicated in various processes of early embryogenesis. 27,30 SYT14 participates in pathomechanical neurodegeneration and contributes to abnormal neurodevelopment. 31 Previous studies found that the expression of Syt14 was highly restricted to the mouse heart and testis but absent in the brain, suggesting that Syt14 may be involved in membrane trafficking in specific tissues other than the brain.…”

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

“…We have demonstrated that HMGN2 interacts with Pitx2 and Sox2 to form an inactive complex to inhibit Pitx2 and Sox2 DNA-binding activity ( 23 , 24 , 25 , 39 ). Dlx2 is required for craniofacial and tooth development, and we have shown that Pitx2 and Lef-1 regulate the Dlx2 promoter ( 23 , 40 , 41 ).…”

“…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.…”

“…Pitx2 has long been considered as a master regulator of the transcriptional hierarchy in early tooth development, including stem cells ( 20 , 21 ). Pitx2 regulates Sox2 and Lef-1 expression in the dental epithelium, and we previously demonstrated that HMGN2 represses Pitx2 and Sox2 transcriptional activation ( 10 , 22 , 23 , 24 , 25 ). The ablation of Lef-1 in the dental epithelium leads to severe tooth developmental defects, causing an arrest during the transition from bud to cap stage ( 26 , 27 ).…”