THE ROLE OF FGFR2 IN PROTEIN SYNTHESIS DURING SKELETAL DEVELOPMENT

 描述（由申请人提供）：骨骼异常影响相当大比例的人口，发病率为每3000例分娩1例。许多骨骼出生缺陷是由于基因突变引起的，这些基因决定了骨骼祖细胞在发育过程中何时何地从自我更新状态转变为终末分化状态。成纤维细胞生长因子受体2（FGFR 2）就是这样一种基因，其突变导致至少10种不同的疾病，这些疾病在颅面和肢体骨骼中表现出异常。FGFR 2通过调节骨祖细胞自我更新或分化的二元选择而充当骨中的关键信号传导节点。然而，FGFR 2控制这些不同细胞结果的机制尚未完全了解。该提案的总体目标是通过揭示核FGFR 2调节核糖体生物合成的机制，更具体地了解FGFR 2如何调节骨骼发育。核糖体的丰度调节细胞蛋白质合成的能力;核糖体组成的异质性调节翻译的特异性。mRNA翻译成蛋白质是基因表达的真正终点，并且由于许多关键调控基因的mRNA和蛋白质水平之间存在差异，因此通过核糖体生物合成控制翻译在调控细胞生长、增殖和分化中至关重要。有强有力的证据表明，这种控制在发育中的骨骼，减少核糖体生物合成是牵连在骨骼异常的发病机制。我们已经发现了令人信服的证据表明FGFR 2紊乱性弯曲骨发育不良综合征（BBDS）是由核糖体生物合成增加引起的。我们发现BBDS中的突变增强了核仁中FGFR 2的正常活性，在那里它激活rDNA转录，这是构建核糖体的限速步骤。FGFR 2介导的rDNA转录增加提高了核糖体的数量，并且与骨祖细胞以分化为代价的增殖激增一致。该提议将检验核FGFR 2通过核糖体生物合成调节蛋白质合成来调节骨骼祖细胞发育的假设。在目的1中，我们将区分骨形成过程中细胞核和细胞膜FGFR 2信号传导的确切作用。在目标2中，我们将定义核FGFR 2如何调节骨骼祖细胞中的核糖体合成。在目标3中，我们将确定增加的rRNA通过调节产生的蛋白质的特性和量来调节骨骼祖细胞发育的程度。这一贡献将产生重大而广泛的影响，因为它将1）从根本上促进我们对FGFR 2和核糖体功能障碍引起的疾病（包括出生缺陷和癌症）的基础机制的理解，2）为靶向核FGFR 2的治疗策略创造新的机会，并在这些疾病中内在地纠正异常细胞增殖和分化。

 DESCRIPTION (provided by applicant): Skeletal anomalies affect a significant proportion of the population, with an incidence rate of 1 case per 3000 births. Numerous skeletal birth defects arise as a consequence of mutations in genes that define when and where skeletal progenitor cells transition from a self-renewing state to one of terminal differentiation during development. Fibroblast Growth Factor Receptor 2 (FGFR2) is one such gene whose mutations are responsible for at least 10 distinct disorders that exhibit abnormalities within the craniofacial ad limb skeleton. FGFR2 acts as a key signaling node in bone by regulating the binary choice of osteoprogenitor cells to either self-renew or to differentiate. However, the mechanism by which FGFR2 controls these distinct cellular outcomes is not completely understood. The overall objective of this proposal is to understand with much greater specificity how FGFR2 regulates skeletal development by revealing the mechanism through which nuclear FGFR2 regulates ribosome biogenesis. The abundance of ribosomes regulates a cell's capacity for protein synthesis; heterogeneities in the composition of ribosomes regulate specificity in translation. Translation of mRNA into protein is the true endpoint of gene expression and because there is a discrepancy between mRNA and protein levels for many key regulatory genes, controlling translation through ribosome biogenesis is critical in regulating cell growth, proliferation, and differentiation. There is strong evidence for such control in the developing skeleton where decreased ribosome biogenesis is implicated in the pathogenesis of skeletal anomalies. We have uncovered compelling evidence that the FGFR2-disorder Bent Bone Dysplasia Syndrome (BBDS) is cause by increased ribosome biogenesis. We found that the mutations in BBDS enhance a normal activity for FGFR2 in the nucleolus where it activates rDNA transcription, the rate-limiting step in building ribosomes. FGFR2-mediated increase in rDNA transcription elevates the number of ribosomes and is coincident with an upsurge in proliferation at the expense of differentiation in osteoprogenitor cells. This proposal will test the hypothesis that nuclear FGFR2 regulates skeletal progenitor cell development by modulating protein synthesis via ribosome biogenesis. In Aim 1, we will distinguish the precise roles of nuclear and membrane FGFR2 signaling during bone formation. In Aim 2, we will define how nuclear FGFR2 regulates ribosome synthesis in skeletal progenitor cells. In Aim 3, we will determine the extent to which increased rRNA regulates development of skeletal progenitor cells by modulating the identity and amount of proteins produced. This contribution will have significant and broad impact because it will 1) fundamentally advance our understanding of the mechanisms underpinning diseases caused by FGFR2 and ribosome dysfunction, including birth defects and cancer, and 2) create new opportunities for therapeutic strategies that target nuclear FGFR2 and intrinsically correct aberrant cell proliferation and differentiation in these diseases.