Exploring the molecular basis of increased egg production in Drosophila melanogaster induced by nutritive concentrations of lithium

锂一直被认为是一种生物活性物质。在药理学剂量上，它被用于治疗神经系统疾病，并已被证明能促进哺乳动物体细胞干细胞的增殖。然而，在营养上可达到的锂浓度是否表现出有益的生物活性仍存在争议，这将指出锂的基本功能。在我们的初步研究中，我们利用黑腹果蝇来阐明不同饮食锂浓度对选定生活史性状的影响。我们观察到，饲粮中锂浓度≈0.7 mg/L足以显著提高果蝇的产卵量30-35%，这与卵巢中约400个基因的转录水平发生显著变化有关。在预期的DFG项目中，我们将采用不同的喂养方案来解读锂喂养对鸡蛋产量的营养方面的影响，如剂量依赖性、可逆性、其他金属阳离子的竞争性抑制和跨代效应。这些实验还将阐明膳食锂是否会影响与年龄相关的产蛋量下降和雄性生育能力。营养锂水平可引起卵发生过程不同阶段的变化。为了解决这一点，我们将主要通过显微镜方法确定饮食中锂对生殖系干细胞、生殖系进展和排卵的影响。我们的初步研究表明，膳食锂影响胰岛素信号通路、GSK3/Sgg活性和章鱼胺信号。通过采用不同的遗传策略，包括细胞消融、器官/组织特异性过表达/RNAi和突变株，结合分析和分子生物学方法，我们将研究锂是否与这些途径相互作用。在约0.7 mg/L锂对卵巢表达改变的400个基因中，我们选择了候选基因。它们的转录反应将通过qRT-PCR验证，然后通过报告基因方法确定它们的表达模式。为了评估它们在卵子发生中的作用，我们将使用器官/组织特异性过表达/RNAi和突变株。此外，我们将使用硅工具在400个基因的启动子区域中识别推定的转录因子结合位点，这可能会导致我们发现锂响应转录因子。

Lithium has long been known as a bioactive substance. In pharmacological doses, it is used to treat neurological diseases and has been shown to promote mammalian somatic stem cell proliferation. However, it is still under debate whether nutritionally achievable concentrations of lithium exhibit beneficial bioactivity, which would point to an essential function. In our preliminary studies, we used Drosophila melanogaster to elucidate the impact of different dietary lithium concentrations on selected life history traits. We observed that a dietary lithium concentration of ≈0.7 mg/L was sufficient to significantly enhance the egg production of fruit flies by 30-35%, which was associated with a significant change in the transcript level of about 400 genes in the ovaries. In the anticipated DFG project, we will apply different feeding regimens to decipher nutritional aspects of lithium feeding with respect to egg production such as dose-dependency, reversibility, competitive inhibition by other metal cations, and transgenerational effects. These experiments shall also elucidate whether dietary lithium affects the age-related egg production decline and male fertility. Nutritive lithium level may induce changes in distinct steps of the oogenesis process. To address this point, we will determine the impact of dietary lithium on germline stem cells, germline progression, and ovulation mainly by microscopy methods. Our preliminary studies suggest that dietary lithium affects the insulin signaling pathway, GSK3/Sgg activity and octopamine signaling. By employing different genetic strategies including cell ablation, organ/tissue-specific overexpression/RNAi and mutant strains in combination with analytical and molecular biological methods we will investigate whether lithium interacts with these pathways. Of the 400 genes whose expression was changed in ovaries by ≈0.7 mg/L lithium, we have selected candidate genes. Their transcriptional response will be verified by qRT-PCR, before their expression pattern will be determined by reporter gene approaches. To evaluate their putative role in oogenesis, we will employ organ/tissue-specific overexpression/RNAi and mutant strains. Moreover, we will use in silico tools to identify putative transcription factor binding sites in the promotor regions of the 400 genes, which may lead us to the discovery of lithium-responsive transcription factors.