Hypomorphic and dominant-negative impact of truncated SOX9 dysregulates Hedgehog-Wnt signaling, causing campomelia.
Hypomorphic and dominant-negative impact of truncated SOX9 dysregulates Hedgehog-Wnt signaling, causing campomelia.
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DOI：
10.1073/pnas.2208623119
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发表时间：
2023-01-03
影响因子：
11.1
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中科院分区：
文献类型：
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SOX 9杂合突变导致Campomelia发育不良的骨骼畸形和弯曲骨。骨弯曲的原因以及类似的分子机制是否适用于体内所有SOX 9杂合突变尚不清楚。在这项研究中，我们产生了一个小鼠相当于人CD SOX 9 Y 440 X突变，截短的C-末端反式激活结构域。我们发现，与无效突变不同，Sox 9 Y 440 X的杂合性对WNT和HH信号传导产生细胞自主和非细胞自主的显性负效应，使成骨失调，导致畸形。我们的研究为SOX 9对人类骨骼形态发生的分子控制提供了机制性的见解，这与骨形状的正常控制，限制生命的先天性生长缺陷以及临床情况下软骨成骨的重演过程有关，例如在骨折修复过程中。软骨形成转录因子SOX 9的单倍不足可导致肢畸形发育不良（CD），一种常染色体显性骨骼畸形综合征，因为杂合子Sox 9缺失小鼠重现弯曲的肢体（肢畸形）和其他一些与CD相关的表型。然而，体外细胞分析表明，单倍不足可能不适用于某些突变，特别是那些截短蛋白质的突变，但在这些情况下，缺乏体内证据，潜在的机制是未知的。在这里，使用条件性小鼠突变体，我们比较了杂合Sox 9无效突变（Sox 9 +/−）与Sox 9 +/Y 440 X CD突变的影响，该突变截短了C末端反式激活结构域，但保留了DNA结合结构域。虽然一些Sox 9 +/Y 440 X小鼠存活，但所有Sox 9 +/−小鼠均在围产期死亡。然而，与Sox 9 +/−相比，Sox 9 +/Y 440 X的骨骼缺陷更严重，发育中的肢体软骨中的IHH信号显著增强。在软骨细胞-成骨细胞谱系中特异性激活Sox 9 Y 440 X引起较温和的campomelia，并揭示了作用于软骨膜中软骨细胞分化和成骨的细胞和非细胞自主机制。对发育中的Sox 9 +/Y 440 X肢体的转录组分析揭示了细胞外基质基因表达失调，以及与异常WNT和HH信号传导一致的变化。S 0X 9 Y 440 X不能与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。我们认为，相邻软骨膜中HH信号的增强会诱导不对称的局部过度软骨膜成骨，从而导致畸形。我们的研究表明，SOX 9 Y 440 X的单倍不足/亚型和显性负性作用，细胞自主和非细胞自主机制，以及WNT和HH信号转导失调，是人类campomelia的原因。
SOX9 heterozygous mutations cause skeletal malformation and bent bones of Campomelia Dysplasia. The cause of bent bones and whether similar molecular mechanisms apply in vivo for all heterozygous mutations in SOX9 are unclear. In this study, we generated a mouse equivalent of the human CD SOX9Y440X mutation, which truncates the C-terminal transactivation domain. We discovered, unlike the null mutation, heterozygosity for Sox9Y440X exerts cell autonomous and noncell autonomous dominant-negative effects on WNT and HH signaling, dysregulating osteogenesis, causing campomelia. Our study provides mechanistic insight into SOX9’s molecular control of human skeletal morphogenesis, that is relevant for normal control of bone shapes, life-limiting congenital growth defects, and the recapitulated processes of chondroosteogenesis in clinical scenarios such as during fracture repair. 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.
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DOI：
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影响因子：
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