SOX9的单倍体不足,SOX9是软骨形成的主要转录因子,可以作为血球发育不良(CD)的基础,常染色体显性骨骼畸形综合征,因为杂合子Sox9缺失小鼠概括了弯曲的肢体(pampomelia)和其他一些与CD相关的表型。然而,体外细胞试验表明单倍体不足可能不适用于某些突变,尤其是那些截短蛋白质的,但在这些病例中,缺乏体内证据,潜在机制未知。这里,使用条件小鼠突变体,我们比较了杂合Sox9无效突变(Sox9+/-)与截短C端反式激活结构域但保留DNA结合结构域的Sox9+/Y440XCD突变的影响.虽然一些Sox9+/Y440X小鼠存活,所有Sox9+/-小鼠围产期死亡。然而,与Sox9+/-相比,Sox9+/Y440X中的骨骼缺损更为严重,发育中的肢体软骨中的IHH信号显着增强。特别是在软骨细胞-成骨细胞谱系中激活Sox9Y440X引起温和的喜马拉雅,并揭示了作用于软骨膜软骨细胞分化和成骨的细胞和非细胞自主机制。发展中的Sox9/Y440X四肢的转录组分析显示细胞外基质基因的表达失调,以及与异常WNT和HH信号一致的变化。SOX9Y440X未能与β-连环蛋白相互作用,并且在基于细胞的测定中不能抑制Ihh的反式激活。我们建议在相邻的软骨膜中增强的HH信号传导会诱导不对称的局部过度的软骨膜成骨作用,从而导致斑马病。我们的研究暗示了SOX9Y440X的单倍不足/双态和显性负作用,细胞自主和非细胞自主机制,以及WNT和HH信号传导失调,作为人类斑马病的原因。
Haploinsufficiency for SOX9, the master chondrogenesis transcription factor, can underlie campomelic dysplasia (CD), an autosomal dominant skeletal malformation syndrome, because heterozygous Sox9 null mice recapitulate the bent limb (campomelia) and some other phenotypes associated with CD. However, in vitro cell assays suggest haploinsufficiency may not apply for certain mutations, notably those that truncate the protein, but in these cases in vivo evidence is lacking and underlying mechanisms are unknown. Here, using conditional mouse mutants, we compared the impact of a heterozygous Sox9 null mutation (Sox9+/-) with the Sox9+/Y440X CD mutation that truncates the C-terminal transactivation domain but spares the DNA-binding domain. While some Sox9+/Y440X mice survived, all Sox9+/- mice died perinatally. However, the skeletal defects were more severe and IHH signaling in developing limb cartilage was significantly enhanced in Sox9+/Y440X compared with Sox9+/-. Activating Sox9Y440X specifically in the chondrocyte-osteoblast lineage caused milder campomelia, and revealed cell- and noncell autonomous mechanisms acting on chondrocyte differentiation and osteogenesis in the perichondrium. Transcriptome analyses of developing Sox9+/Y440X limbs revealed dysregulated expression of genes for the extracellular matrix, as well as changes consistent with aberrant WNT and HH signaling. SOX9Y440X failed to interact with β-catenin and was unable to suppress transactivation of Ihh in cell-based assays. We propose enhanced HH signaling in the adjacent perichondrium induces asymmetrically localized excessive perichondrial osteogenesis resulting in campomelia. Our study implicates combined haploinsufficiency/hypomorphic and dominant-negative actions of SOX9Y440X, cell-autonomous and noncell autonomous mechanisms, and dysregulated WNT and HH signaling, as the cause of human campomelia.