Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei, Taiwan.
Biol Reprod. 2012 May 31;86(5):158, 1-9. doi: 10.1095/biolreprod.111.096172. Print 2012 May.
Although differential screening-selected gene aberrative in neuroblastoma (DAN, official symbol NBL1) is the founding member of the DAN subfamily of bone morphogenetic protein (BMP) antagonists, its antagonizing targets, gene regulation, and physiological functions remain unclear. Using diverse cell expression systems, we found that the generation of bioactive DAN is likely to be cell type specific. Unlike other phylogenetically close members, which are covalently linked homodimers, DAN forms a noncovalently linked homodimer during folding. Purified recombinant DAN specifically blocked signaling of BMP2 and BMP4 but not that of other ovarian-expressed transforming growth factor-beta members. Although widely distributed in many organs, DAN transcript level was periodically regulated by gonadotropins. Ovarian microdissection indicated that NBL1 (DAN) mRNA is mainly expressed in granulosa cells, where its transcript level is up-regulated by the gonadotropin-driven cAMP cascade. We further investigated the local regulation and ovarian functions of DAN. NBL1 (DAN) mRNA expression in granulosa cells was up-regulated by oocyte-derived growth differentiation factor 9 (GDF9), whereas treatment with DAN significantly reversed the inhibitory effect of BMP4 on follicle-stimulating hormone-induced progesterone production in cultured granulosa cells. Our findings suggest the DAN gradient in granulosa cells, established by oocyte-derived GDF9, may serve as an antagonist barrier that modulates the actions of theca-derived BMP4 and granulosa/theca-derived BMP2 during folliculogenesis both spatially and temporally.
虽然神经母细胞瘤（DAN，官方符号 NBL1）中的差异筛选基因异常是骨形态发生蛋白（BMP）拮抗剂 DAN 亚家族的创始成员，但它的拮抗靶标、基因调控和生理功能仍不清楚。使用不同的细胞表达系统，我们发现生物活性 DAN 的产生可能具有细胞类型特异性。与其他进化上密切相关的成员不同，它们是共价连接的同源二聚体，DAN 在折叠过程中形成非共价连接的同源二聚体。纯化的重组 DAN 特异性阻断 BMP2 和 BMP4 的信号传导，但不阻断其他卵巢表达的转化生长因子-β成员的信号传导。尽管广泛分布于许多器官中，但 DAN 转录本水平受促性腺激素周期性调节。卵巢微切割表明，NBL1（DAN）mRNA 主要在颗粒细胞中表达，其转录本水平受促性腺激素驱动的 cAMP 级联上调。我们进一步研究了 DAN 的局部调节和卵巢功能。颗粒细胞中 NBL1（DAN）mRNA 的表达受卵源性生长分化因子 9（GDF9）上调，而 DAN 处理显著逆转了 BMP4 对卵泡刺激素诱导的培养颗粒细胞中孕激素产生的抑制作用。我们的发现表明，由卵源性 GDF9 建立的颗粒细胞中的 DAN 梯度可能作为一种拮抗剂屏障，在时空上调节卵母细胞衍生的 BMP4 和颗粒细胞/膜细胞衍生的 BMP2 在卵泡发生过程中的作用。
