Case report: A novel de novo loss of function variant in the DNA-binding domain of TBX2 causes severe osteochondrodysplasia

Background: T-box family members are transcription factors characterized by highly conserved residues corresponding to the DNA-binding domain known as the T-box. TBX2 has been implicated in several developmental processes, such as coordinating cell fate, patterning, and morphogenesis of a wide range of tissues and organs, including lungs, limbs, heart, kidneys, craniofacial structures, and mammary glands. Methods: In the present study, we have clinically and genetically characterized a proband showing a severe form of chondrodysplasia with developmental delay. Whole-exome sequencing (WES), Sanger sequencing, and 3D protein modeling were performed in the present investigation. Results: Whole-exome sequencing revealed a novel nonsense variant (c.529A>T; p.Lys177*; NM_005994.4) in TBX2. 3D-TBX2 protein modeling revealed a substantial reduction of the mutated protein, which might lead to a loss of function (LOF) or nonsense-mediated decay (NMD). Conclusion: This study has not only expanded the mutation spectrum in the gene TBX2 but also facilitated the diagnosis and genetic counseling of related features in affected families.