Mesoderm-specific Stat3 deletion affects expression of Sox9 yielding Sox9-dependent phenotypes.
Mesoderm-specific Stat3 deletion affects expression of Sox9 yielding Sox9-dependent phenotypes.
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DOI：
10.1371/journal.pgen.1006610
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发表时间：
2017-02
期刊：
影响因子：
4.5
通讯作者：
Perantoni AO
中科院分区：
文献类型：
--
作者：
Hall MD;Murray CA;Valdez MJ;Perantoni AO
到目前为止，编码区内的突变和SOX 9基因周围的易位都构成了大多数支持人类Campomelic发育不良（CD）的遗传病变。虽然病理性编码区突变通常会导致非功能性SOX 9蛋白，但人们对控制正常SOX 9表达的机制以及随后哪些信号通路可能被SOX 9基因周围发生的改变中断知之甚少。在这里，我们报告的鉴定Stat 3作为一个关键的调节剂的Sox 9在新生软骨和发育中的软骨细胞的表达。Stat 3的表达是主要的中胚层起源的组织，其条件消融使用中胚层特异性TCre，在体内，导致侏儒症和骨骼缺陷的CD的特点。具体而言，Stat 3损失导致生长板肥大软骨细胞的扩张和正常软骨内骨化的失调，在所有检查的骨。用Sox 9 Cre驱动程序条件性缺失Stat 3产生与Sox 9 +/-小鼠中描述的那些相似的腭和气管不规则性。此外，Stat 3的中胚层缺失导致体内Sox 9表达和功能的整体胚胎下调。离体机制实验表明，Stat 3可以通过在激活后结合其近端启动子来直接激活Sox 9的表达。这些发现阐明了Stat 3在骨骼发育过程中通过调节关键因子Sox 9在软骨细胞中的新作用。重要的是，它们进一步提供了除了Sox 9本身之外的基因产物调节的第一个证据，该基因产物能够模拟CD的病理学方面，并强调了患有该疾病的患者的潜在有价值的治疗靶点。Campomelic（希腊语：“弯曲的肢体”）发育不良是一种经常致死的常染色体显性遗传疾病。典型的临床特征包括有角的长骨、肩胛骨发育不全、腭裂、畸形足、呼吸困难和外生殖器不清。迄今为止，与这种疾病有关的唯一基因是SOX 9，它是软骨细胞发育的关键因素。SOX 9编码区内的有害突变占大多数病例;然而，染色体断裂或易位标志着一部分病例，可能是通过改变SOX 9的表达。我们发现Stat 3功能丧失突变小鼠表现出与肢端发育不良一致的特征，包括侏儒症、四肢弯曲、腭裂、喉气管软化和异常生长板肥大软骨细胞。重要的是，我们还证明了从软骨祖细胞中切除Stat 3会降低体内Sox 9的功能水平。最后，我们表明，Stat 3可以直接调节Sox 9的表达，通过物理相互作用的启动子在响应刺激。总的来说，我们的研究结果表明，SOX 9的非编码区突变，调节可及性或功能的Stat-binding元素，可能会导致SOX 9的生理水平降低。我们的模型首次表明，除了Sox 9之外的基因的调节能够重现与Campomelic发育不良相关的一大部分病理，这可能用于未来的治疗干预。
To date, mutations within the coding region and translocations around the SOX9 gene both constitute the majority of genetic lesions underpinning human campomelic dysplasia (CD). While pathological coding-region mutations typically result in a non-functional SOX9 protein, little is known about what mechanism(s) controls normal SOX9 expression, and subsequently, which signaling pathways may be interrupted by alterations occurring around the SOX9 gene. Here, we report the identification of Stat3 as a key modulator of Sox9 expression in nascent cartilage and developing chondrocytes. Stat3 expression is predominant in tissues of mesodermal origin, and its conditional ablation using mesoderm-specific TCre, in vivo, causes dwarfism and skeletal defects characteristic of CD. Specifically, Stat3 loss results in the expansion of growth plate hypertrophic chondrocytes and deregulation of normal endochondral ossification in all bones examined. Conditional deletion of Stat3 with a Sox9Cre driver produces palate and tracheal irregularities similar to those described in Sox9+/- mice. Furthermore, mesodermal deletion of Stat3 causes global embryonic down regulation of Sox9 expression and function in vivo. Mechanistic experiments ex vivo suggest Stat3 can directly activate the expression of Sox9 by binding to its proximal promoter following activation. These findings illuminate a novel role for Stat3 in chondrocytes during skeletal development through modulation of a critical factor, Sox9. Importantly, they further provide the first evidence for the modulation of a gene product other than Sox9 itself which is capable of modeling pathological aspects of CD and underscore a potentially valuable therapeutic target for patients with the disorder. Campomelic (Greek: “bent limb”) dysplasia is an often-lethal, autosomal-dominant genetic disorder. Typical clinical features include angular long bones, hypoplastic scapulae, cleft palate, clubbed feet, labored breathing and ambiguous external genitalia. To date, the only gene implicated in this disease is SOX9, a critical factor in chondrocyte development. Deleterious mutations within the coding region of SOX9 account for a majority of cases; however, chromosomal breakages or translocations mark a subset of cases, presumably by altering expression of SOX9. We have found that Stat3 loss-of-function mutant mice exhibit features consistent with campomelic dysplasia including dwarfism, bent limbs, cleft palate, laryngotracheomalacia and abnormal growth plate hypertrophic chondrocytes. Importantly, we also demonstrate that ablation of Stat3 from chondroprogenitors reduces the functional level of Sox9 in vivo. Finally, we show that Stat3 may directly regulate Sox9 expression by physically interacting with the promoter in response to stimulation. Taken in total, our findings demonstrate that non-coding region mutations in SOX9, which modulate the accessibility or functionality of Stat-binding elements, may result in decreased physiological levels of SOX9. Our model suggests for the first time, the modulation of a gene other than Sox9 that is capable of recapitulating a large subset of pathologies associated with campomelic dysplasia, which may be exploited for future therapeutic intervention.