Expression Profiling of Dll1 mutant mouse line

BACKGROUND: The Notch signaling pathway is an evolutionary conserved signal transduction pathway involved in embryonic patterning and regulation of cell fates during development and self-renewal. Recent studies have demonstrated that this pathway is integral to a complex system of interactions, involving as well other signal transduction pathways, and implicated in distinct human diseases. Delta-like 1 (Dll1) is one of the known ligands of the Notch receptors. The role of the Notch ligands is less well understood. Loss-of-function of Dll1 leads to embryonic lethality, but reduction of Delta-like 1 protein levels has not been studied in adult stage. METHODOLOGY/PRINCIPAL FINDINGS: Here we present the haploinsufficient phenotype of Dll1 and a missense mutant Dll1 allele (Dll1(C413Y)). Haploinsufficiency leads to a complex phenotype with several biological processes altered. These alterations reveal the importance of Dll1 mainly in metabolism, energy balance and in immunology. The animals are smaller, lighter, with altered fat to lean ratio and have increased blood pressure and a slight bradycardia. The animals have reduced cholesterol and triglyceride levels in blood. At the immunological level a subtle phenotype is observed due to the effect and fine-tuning of the signaling network at the different levels of differentiation, proliferation and function of lymphocytes. Moreover, the importance of the proteolytic regulation of the Notch signaling network emphasized. CONCLUSIONS/SIGNIFICANCE: In conclusion, slight alterations in one player of Notch signaling alter the entire organism, emphasizing the fine-tuning character of this pathway in a high number of processes. Four organs (liver, spleen, thymus, brain) of the Dll1 mutant mouse line analysed by cDNA microarray technology. Experiments include four biological replicates for reference (wildtype) and mutant animals. Two technical replicates for each mutant mouse were performed. As reference pooled RNA of the same organ was used. 50% of the chip hybridizations are dye swap experiments.研究背景：Notch信号通路（Notch signaling pathway）是一条进化保守的信号转导通路，参与胚胎发育过程中的模式形成、细胞命运调控与自我更新。近期研究证实，该通路是复杂互作网络的核心组分，同时与其他信号转导通路存在交互，并与多种人类疾病密切相关。Delta样蛋白1（Delta-like 1, Dll1）是已知的Notch受体配体之一。目前学界对Notch配体的功能认知尚不完善。Dll1功能缺失会导致胚胎致死，但成年阶段Delta样蛋白1水平降低的相关研究尚未开展。 研究方法与主要发现：本研究报道了Dll1单倍剂量不足（haploinsufficiency）表型以及错义突变型Dll1等位基因（Dll1(C413Y)）。单倍剂量不足可引发复杂表型，累及多个生物学过程。这些表型改变揭示了Dll1在代谢、能量平衡及免疫学过程中的关键作用。实验动物体型更小、体重更低，体脂与瘦体重比例异常，同时伴有血压升高与轻度心动过缓；其血液中胆固醇与甘油三酯水平均有所降低。在免疫学层面，由于信号网络在淋巴细胞分化、增殖与功能的不同层级受到调控与微调，仅观察到细微的表型变化。此外，本研究进一步凸显了Notch信号网络蛋白水解调控的重要性。 结论与意义：综上，Notch信号通路任一成员的轻微改变均可影响整个机体，凸显了该通路在众多生理过程中的精细调控特性。本研究通过cDNA微阵列（cDNA microarray）技术，对Dll1突变小鼠品系的四个器官（肝脏、脾脏、胸腺、大脑）进行了分析。实验针对野生型（wildtype）对照与突变体动物各设置了四份生物学重复。每只突变小鼠均开展两次技术重复实验。以同一器官的混合RNA作为对照样本。50%的芯片杂交实验采用了染料互换（dye swap）实验设计。