Expression profiling in the Drosophila eye reveals unexpected repression of Notch signaling by the JAK/STAT pathway

Although the JAK/STAT pathway regulates numerous processes in vertebrates and invertebrates through modulating transcription, its functionally-relevant transcriptional targets remain largely unknown. With one jak and one stat (stat92E), Drosophila provides a powerful system for finding new JAK/STAT target genes. Genome-wide expression profiling on eye discs in which Stat92E is hyperactivated, revealed 584 differentially-regulated genes, including known targets domeless, socs36E and wingless. Other differentially-regulated genes (chinmo, lama, Mo25, Imp-L2, Serrate, Delta) were validated and may represent new Stat92E targets. Genetic experiments revealed that Stat92E cell-autonomously represses Serrate, which encodes a Notch ligand. Loss of Stat92E led to de-repression of Serrate in the dorsal eye, resulting in ectopic Notch signaling and aberrant eye growth there. Thus, our micro-array documents a new Stat92E target gene and a previously-unidentified inhibitory action of Stat92E on Notch signaling. These data suggest that this study will be a useful resource for the identification of additional Stat92E targets. Identification of the JAK/STAT pathway target genes in the Drosophila eye disc Keywords: Genotype comparison Gene expression profiles from five biological replicates of eye discs with yw (control) and GMR-upd (overexpressing JAK/STAT ligand unpaired) were compared using genome wide mRNA expression profiling by Affymetrix genechip arrays (Drosophila 2.0) and key targets were validated by clonal analysis, in situ hybridization, immunohistochemical staining and quantitative real-time PCR.

尽管JAK/STAT通路（JAK/STAT pathway）通过调控转录过程在脊椎动物与无脊椎动物体内调控诸多生理进程，但其功能相关的转录靶标仍在很大程度上未被探明。果蝇（Drosophila）仅拥有单个jak基因与单个stat基因（stat92E），为挖掘新的JAK/STAT通路靶基因提供了极为理想的研究模型。对Stat92E过度激活的果蝇眼盘开展全基因组表达谱分析后，共筛选得到584个差异调控基因，其中包含已知靶标domeless、socs36E与wingless。其余差异调控基因（chinmo、lama、Mo25、Imp-L2、Serrate、Delta）均经实验验证，或为全新的Stat92E靶基因。
遗传实验证实，Stat92E可通过细胞自主性方式抑制编码Notch配体的Serrate的表达。Stat92E功能缺失会导致果蝇背侧眼盘中Serrate的去抑制，进而引发异位Notch信号激活与眼组织异常增生。综上，本研究的微阵列（micro-array）数据不仅揭示了一个新的Stat92E靶基因，还发现了此前未被报道的Stat92E对Notch信号通路的抑制作用。上述研究数据表明，本成果可为后续更多Stat92E靶标的鉴定工作提供极具价值的研究资源。
果蝇眼盘中JAK/STAT通路靶基因的鉴定
关键词：基因型比较
本研究通过Affymetrix基因芯片（Affymetrix genechip arrays，Drosophila 2.0），对yw（对照组）与GMR-upd（过表达JAK/STAT配体unpaired）的眼盘的5个生物学重复样本开展全基因组mRNA表达谱分析，并通过克隆分析、原位杂交、免疫组化染色及实时定量PCR对关键靶标进行了验证。