A Novel Loss-of-Function Variant in TGFBI Associated with Non-Syndromic Orofacial Clefts in a Chinese Pedigree.

Background/Objectives: Non-syndromic orofacial clefts (NSOFCs) are among the most common congenital craniofacial anomalies, with genetic factors playing a major role in their etiology. Transforming growth factor-β-induced (TGFBI) protein is an extracellular matrix protein implicated in cell adhesion and apoptosis. Although experimental studies have implicated TGFBI in palatal fusion, its contribution to human NSOFCs remains unclear. This study investigated the genetic basis of hereditary NSOFCs in a Chinese family. The functional consequences of the identified TGFBI variant were subsequently evaluated. Methods: Whole-exome sequencing was performed in a Chinese NSOFC pedigree, followed by Sanger validation and ophthalmological evaluation. The functional impact of the identified variant was investigated through evolutionary and structural analyses, TGFBI expression analysis during mouse palatal development, and cellular functional assays. Results: A novel heterozygous stop-gain variant in TGFBI (NM_000358.3:c.230C > A; p.Ser77X) was identified in affected family members but not in the unaffected father. No corneal abnormalities were observed in variant carriers. TGFBI was expressed in the midline epithelial seam during palatal fusion. The p.Ser77X variant generated a truncated protein lacking all four FAS1 domains and the C-terminal RGD motif, resulting in abnormal localization, impaired cellular apoptosis and proliferation, and altered p38-MAPK signaling. Conclusions: This study identifies a rare loss-of-function TGFBI variant associated with NSOFCs and provides genetic and functional evidence supporting a role for TGFBI variation in human palatal development.