TBX1 protein interactions and microRNA-96-5p regulation controls cell proliferation during craniofacial and dental development: implications for 22q11.2 deletion syndrome

Abstract

T-box transcription factor TBX1 is the major candidate gene for 22q11.2 deletion syndrome (22q11.2DS, DiGeorge syndrome/Velo-cardio-facial syndrome), whose phenotypes include craniofacial malformations such as dental defects and cleft palate. In this study, Tbx1 was conditionally deleted or over-expressed in the oral and dental epithelium to establish its role in odontogenesis and craniofacial developmental. Tbx1 lineage tracing experiments demonstrated a specific region of Tbx1-positive cells in the labial cervical loop (LaCL, stem cell niche). We found that Tbx1 conditional knockout (Tbx1(cKO)) mice featured microdontia, which coincides with decreased stem cell proliferation in the LaCL of Tbx1(cKO) mice. In contrast, Tbx1 over-expression increased dental epithelial progenitor cells in the LaCL. Furthermore, microRNA-96 (miR-96) repressed Tbx1 expression and Tbx1 repressed miR-96 expression, suggesting that miR-96 and Tbx1 work in a regulatory loop to maintain the correct levels of Tbx1. Cleft palate was observed in both conditional knockout and over-expression mice, consistent with the craniofacial/tooth defects associated with TBX1 deletion and the gene duplication that leads to 22q11.2DS. The biochemical analyses of TBX1 human mutations demonstrate functional differences in their transcriptional regulation of miR-96 and co-regulation of PITX2 activity. TBX1 interacts with PITX2 to negatively regulate PITX2 transcriptional activity and the TBX1 N-terminus is required for its repressive activity. Overall, our results indicate that Tbx1 regulates the proliferation of dental progenitor cells and craniofacial development through miR-96-5p and PITX2. Together, these data suggest a new molecular mechanism controlling pathogenesis of dental anomalies in human 22q11.2DS.

22q11.2 Deletion Syndrome due to a Translocation t(6;22) in a Patient Conceived via in vitro Fertilization

“…The TBX1 (Tbox transcription factor) gene is considered the major candidate for 22q11.2 deletion syndrome [Gao et al, 2015], being associated with cardiovascular defects [Lindsay et al, 2001;Jerome and Papaioannou, 2001], middle and inner ear defects, resulting in sensorineural hearing loss [Funke et al, 2001], and with craniofacial and dental Dantas et al Mol Syndromol 2015;6:242-247 DOI: 10.1159/000441243 246 development delay [Gao et al, 2015]; features we found in our patient.…”

Dental Findings in Patients With Non-surgical Hypoparathyroidism and Pseudohypoparathyroidism: A Systematic Review

“…Low levels of PTH in Ns-HypoPT and end-organ resistance to PTH in PHP leads to hypocalcemia. Hypocalcemia is hypothesized as one of the potential causes of disturbances of the tooth development, e.g., enamel opacities and enamel hypoplasia (Garfunkel et al, 1979; Gao et al, 2015). Studies on dental manifestations of the various types of Ns-HypoPT and PHP, e.g., enamel hypoplasia, enamel opacities, hypodontia, root deviations, and eruption disturbances are, however, often mentioned with only few references (Goswami et al, 2009; Velez et al, 2009; Kamarthi et al, 2013).…”

Candidate gene analyses of 3-dimensional dentoalveolar phenotypes in subjects with malocclusion

“…TBX1 is a major candidate gene causal for 22q11 deletion syndrome associated with congenital heart defects resulting from incorrect left-to-right patterning important for asymmetric cardiac morphogenesis 42 as well as craniofacial and dental anomalies including cleft palate. 43 The LIM protein AJUBA has previously shown an association with soft tissue facial width phenotypes, 44,45 and it is also required for expression of early developmental genes that determine left-right body axis patterning. 46 As discussed above, SNAI3 was largely associated with skeletal phenotypes in malocclusion patients in our previous study.…”