患者源性诱导性多能干细胞模型揭示TBX6相关先天性脊柱侧弯患者黏蛋白型O-聚糖生物合成相关转录程序的失调现象

Abstract

TBX6-associated congenital scoliosis (TACS) is a genetic subtype of congenital scoliosis caused by reducedTBX6gene dosage, most commonly through compound inheritance of a rare loss-of-function allele and a hypomorphic T-C-A haplotype. However, the mechanisms linking TBX6 dysfunction to impaired human skeletal development remain unclear. Here, we established a patient-derived induced pluripotent stem cell (iPSC) model of TACS and recapitulated key stages of axial skeletal development through stepwise differentiation into paraxial mesoderm, nascent somites, sclerotome, and subsequently osteogenic and chondrogenic lineages. TACS-derived cells showed impaired differentiation, with reduced mineralized matrix deposition and diminished cartilage matrix formation. Bulk transcriptomic profiling revealed marked alterations in both lineages. Notably, mu-cin-type O-glycan biosynthesis was consistently enriched among downregulated genes in osteogenic and chondrogenic cells and was also significantly represented among genes commonly downregulated across both lineages. qRT-PCR further confirmed reduced expression ofGALNT3,GALNT5,GALNT7,GALNT10,GCNT1, andST6GALNAC2, which participate in distinct steps of mucin-type O-glycan biosynthesis. Consistent with these transcriptional alterations, Tn-antigen staining showed reduced Tn-associated O-GalNAc signals in TACS-derived osteogenic and chondrogenic cells. In silico promoter analysis identified candidate sequences matching the TBX6-binding motif within the upstream regions of these genes, providing potential regulatory regions for future experimental investigation. Collectively, these results establish a human iPSC model for TACS and identify coordinated dysregulation of a mucin-type O-glycan biosynthesis-related transcriptional program, accompanied by reduced Tn-associated O-GalNAc signals, as molecular features associated with impaired osteochondral differentiation in this model. These findings should be interpreted within the conte