MAML1 enhances the transcriptional activity of Runx2 and plays a role in bone development.
MAML1 enhances the transcriptional activity of Runx2 and plays a role in bone development.
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DOI：
10.1371/journal.pgen.1003132
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发表时间：
2013
期刊：
影响因子：
4.5
通讯作者：
Asahara H
中科院分区：
文献类型：
--
作者：
Watanabe T;Oyama T;Asada M;Harada D;Ito Y;Inagawa M;Suzuki Y;Sugano S;Katsube K;Karsenty G;Komori T;Kitagawa M;Asahara H
Mastermind-like 1 (MAML1) 是 Notch 信号通路中的转录共激活因子。然而最近，一些报告揭示了 MAML1 独立于 Notch 信号通路的新颖且独特的作用。我们发现 MAML1 增强了 runt 相关转录因子 2 (Runx2) 的转录活性，Runx2 是成骨细胞分化、软骨细胞增殖和成熟所必需的转录因子。 MAML1 显着增强了 Runx2 介导的 p6OSE2-Luc 报告基因的转录，其中荧光素酶表达由来自 Runx2 调节的骨钙素基因启动子的成骨细胞特异性元件 2 (OSE2) 的 6 个拷贝控制。有趣的是，缺乏 N 端 Notch 结合域的 MAML1 缺失突变体也增强了 Runx2 介导的转录。此外，Notch信号传导的抑制并不影响MAML1对Runx2的作用，这表明MAML1对Runx2的激活可能是以不依赖Notch的方式引起的。在小鼠多能间充质细胞系 C3H10T1/2 中，MAML1 的过表达暂时增强了 Runx2 介导的碱性磷酸酶的表达，碱性磷酸酶是成骨细胞分化的早期标志物。胚胎第 16.5 天 (E16.5) 的 MAML1−/− 胚胎的骨长度比野生型胚胎短。股骨骨干初级海绵体面积变窄。在 E14.5 时，观察到 II 型胶原蛋白 α 1 (Col2a1) 和 Sox9 表达区域扩大（软骨细胞分化标志物），以及 X 型胶原蛋白 α 1 (Col10a1) 表达区域减少（肥大软骨细胞标志物）。这些观察结果表明 MAML1−/− 小鼠的软骨细胞成熟受到损害。 MAML1 增强 Runx2 的转录活性，并在骨骼发育中发挥作用。为了鉴定参与骨和软骨发育和/或体内平衡的新分子，我们利用了大约 10,000 个阵列且可寻址的 cDNA 克隆，这使得系统、有效和公正地筛选 cDNA 编码因子可以通过激活 Runx2（骨发育的主调节因子）来激活关键的骨分化活性。我们分析了 MAML1−/− 小鼠，以研究 MAML1 在骨骼发育中的作用。胚胎第 14.5 天和第 16.5 天的 MAML1−/− 胚胎的骨长度比野生型胚胎短。股骨骨干初级海绵体面积变窄，表明软骨细胞成熟受损。这表明MAML1在骨骼的正常发育中发挥着重要作用，可能为我们识别骨疾病的潜在治疗靶点提供新的基础。
Mastermind-like 1 (MAML1) is a transcriptional co-activator in the Notch signaling pathway. Recently, however, several reports revealed novel and unique roles for MAML1 that are independent of the Notch signaling pathway. We found that MAML1 enhances the transcriptional activity of runt-related transcription factor 2 (Runx2), a transcription factor essential for osteoblastic differentiation and chondrocyte proliferation and maturation. MAML1 significantly enhanced the Runx2-mediated transcription of the p6OSE2-Luc reporter, in which luciferase expression was controlled by six copies of the osteoblast specific element 2 (OSE2) from the Runx2-regulated osteocalcin gene promoter. Interestingly, a deletion mutant of MAML1 lacking the N-terminal Notch-binding domain also enhanced Runx2-mediated transcription. Moreover, inhibition of Notch signaling did not affect the action of MAML1 on Runx2, suggesting that the activation of Runx2 by MAML1 may be caused in a Notch-independent manner. Overexpression of MAML1 transiently enhanced the Runx2-mediated expression of alkaline phosphatase, an early marker of osteoblast differentiation, in the murine pluripotent mesenchymal cell line C3H10T1/2. MAML1−/− embryos at embryonic day 16.5 (E16.5) had shorter bone lengths than wild-type embryos. The area of primary spongiosa of the femoral diaphysis was narrowed. At E14.5, extended zone of collagen type II alpha 1 (Col2a1) and Sox9 expression, markers of chondrocyte differentiation, and decreased zone of collagen type X alpha 1 (Col10a1) expression, a marker of hypertrophic chondrocyte, were observed. These observations suggest that chondrocyte maturation was impaired in MAML1−/− mice. MAML1 enhances the transcriptional activity of Runx2 and plays a role in bone development. To identify new molecules involved in bone and cartilage development and/or homeostasis, we utilized approximately 10,000 arrayed and addressable cDNA clones, which allowed systematic, efficient, and unbiased screening of cDNAs encoding factors that could activate critical bone differentiation activity via activation of Runx2, master regulator of bone development. We analyzed MAML1−/− mice to investigate the role of MAML1 in bone development. MAML1−/− embryos at embryonic day 14.5 and 16.5 had shorter bone lengths than wild-type embryos. The area of primary spongiosa of the femoral diaphysis was narrowed, indicated that chondrocyte maturation was impaired. This revealed that MAML1 plays an important role in proper bone development and may provide us with a new basis for identifying potential therapeutic targets for bone diseases.
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