Department of Biomedical Sciences, Chang Gung University, Kwei-Shan, Tao-Yuan , Taiwan.
J Biomed Sci. 2011 Jun 17;18(1):42. doi: 10.1186/1423-0127-18-42.
The conserved Notch signaling pathway regulates cell fate decisions and maintains stem cells in multicellular organisms. Up-regulation of Notch signaling is observed in several types of cancer and is causally involved in proliferation and survival of cancer cells. Thus, it is of great interest to look for anti-Notch reagents for therapeutic purposes. In model animal Drosophila, Notch signaling restricts selection of sensory organ precursors (SOPs) during external sensory (ES) organ development. To look for novel genes that can suppress Notch signaling, we performed a gain-of-function modifier screen to look for genes that enhance the phenotype of ectopic ES organs induced by overexpression of phyllopod, a gene required for SOP specification.
From the gain-of-function screen, we discovered that overexpression of polished rice/tarsal-less (pri/tal) increases the numbers of ES organs as well as SOPs. pri/tal is a polycistronic gene that contains four short open reading frames encoding three 11-amino acid and one 32-amino acid peptides. Ectopic expression of the 11 amino-acid peptides recapitulates the pri/tal misexpression phenotype in ectopic ES organ formation. In situ hybridization experiment reveals that pri/tal mRNA is expressed in the SOPs of the chemosensory organs and the stretch-sensing chordotonal organs.In Drosophila wing development, the Notch signaling pathway mediates the formation of the dorsal-ventral (DV) compartmental boundary and the restriction of the vein width from the primordial veins, the proveins. We also found that pri/tal mRNA is expressed in the DV boundary and the longitudinal proveins, and overexpression of Pri/Tal peptides disrupts the DV boundary formation and helps to expand the width of the wing vein. Genetic analyses further show that a Notch loss-of-function allele strongly enhances these two phenotypes. Cut and E(spl)mβ are target genes of the Notch pathway in DV boundary formation and vein specification, respectively. We also found that overexpression of Pri/Tal peptides abolishes Cut expression and co-expression of Pri/Tal peptides with phyl strongly reduces E(spl)mβ expression.
We show for the first time that the overexpression of Pri/Tal 11-amino acid peptides disrupts multiple Notch-mediated processes and reduces Notch target gene expression in Drosophila, suggesting that these peptides have novel antagonistic activity to the Notch pathway. Thus, our discovery might provide insights into designing new therapeutic reagents for Notch-related diseases.
保守的 Notch 信号通路调节细胞命运决定并维持多细胞生物中的干细胞。几种类型的癌症中观察到 Notch 信号通路的上调，并且该信号通路在癌细胞的增殖和存活中起因果作用。因此，寻找用于治疗目的的抗 Notch 试剂非常重要。在模式动物果蝇中，Notch 信号通路在外感（ES）器官发育过程中限制感觉器官前体（SOP）的选择。为了寻找可以抑制 Notch 信号通路的新基因，我们进行了功能获得性修饰筛选，以寻找可以增强由 Phyllopod 过表达诱导的异位 ES 器官表型的基因，Phyllopod 是 SOP 特异性所必需的基因。
从功能获得性筛选中，我们发现 polished rice/tarsal-less（pri/tal）的过表达增加了 ES 器官和 SOP 的数量。pri/tal 是一个多顺反子基因，包含四个编码三个 11 个氨基酸和一个 32 个氨基酸肽的短开放阅读框。异位表达 11 个氨基酸肽可重现 pri/tal 异位 ES 器官形成中的异位表达表型。原位杂交实验表明，pri/tal mRNA 在外感化学感觉器官和伸展感觉的神经索中的 SOP 中表达。在果蝇翅膀发育过程中，Notch 信号通路介导背腹（DV）隔室边界的形成和原始静脉，原静脉的脉宽限制。我们还发现 pri/tal mRNA 在 DV 边界和纵向原静脉中表达，并且 Pri/Tal 肽的过表达破坏了 DV 边界的形成并有助于扩大翅膀静脉的宽度。遗传分析进一步表明，Notch 功能丧失等位基因强烈增强了这两种表型。Cut 和 E（spl）mβ 分别是 DV 边界形成和脉管特异性中 Notch 途径的靶基因。我们还发现 Pri/Tal 肽的过表达消除了 Cut 的表达，并且 phyl 与 Pri/Tal 肽的共表达强烈降低了 E（spl）mβ 的表达。
我们首次表明，Pri/Tal 11 个氨基酸肽的过表达破坏了果蝇中多个 Notch 介导的过程并降低了 Notch 靶基因的表达，表明这些肽具有针对 Notch 途径的新拮抗活性。因此，我们的发现可能为设计用于 Notch 相关疾病的新型治疗试剂提供了见解。
