Mammalian milk paradigm secretion, transport functional uptake mobile silen RNA

在植物和无脊椎动物中，长RNA和沉默的小RNA在细胞之间长距离移动，在遥远的组织中发挥调节功能。最近，在哺乳动物体液和细胞外空间分泌的微泡被发现含有RNA，这些，而且，可能在受体细胞内化。在血清中也检测到称为Argonautes（AGO）的sRNA效应蛋白。这些发现促使人们推测，与脂质和/或效应蛋白结合的哺乳动物细胞外RNA可能在被靶细胞/组织摄取后具有生物学功能。然而，目前几乎没有（如果有的话）实验证据支持这一想法。我们的实验室率先研究了 非细胞自主RNAi，是最早在哺乳动物细胞中建立RNA沉默，内膜和囊泡运输之间联系的人之一。最近，我们发现人和牛乳含有生理量的调节性微（mi）RNA，特别是集中在乳脂肪球（MFG）中，乳脂肪球是新生儿的脂肪来源。此外，我们还在MFG和其他乳组分中检测到大量的特定AGO，这表明AGO结合的miRNA和其他RNA可能在喂养期间功能性地转移到新生的肠道上皮细胞中，并且可能转移到远处器官中。利用McManus和Hunter实验室提供的基于小鼠和细胞的强大遗传工具集合，我们在这里提出使用哺乳动物乳汁-一种容易获得和丰富的体液-作为研究的范例（i）支持乳腺分泌miRNA的机制，（ii）含乳miRNA的蛋白质和脂质环境，包括可能的新的乳相关AGO伴侣，（iii）肠道上皮细胞摄取乳汁miRNA的机制，以及（iv）在喂养期间从母体转移到幼崽的乳汁携带的miRNA是否有效地在小鼠新生儿中显示生物活性。从这些知识和植物和寄生无脊椎动物之间跨王国RNAi转移的明确先例中，我们将最终解决，使用我们独特的植物-哺乳动物双重专业知识，如果来自作物的饮食RNA可以被植物喂养的小鼠的肠道上皮功能性吸收。

In plants and invertebrates, long RNAs and silencing small (s)RNAs move between cells and over long distances to exert regulatory functions in remote tissues. Recently, micro-vesicles secreted in mammalian body fluids and in the extra-cellular space were found to contain RNA; these, moreover, might be internalized in recipient cells. sRNA effector proteins called Argonautes (AGOs) were also detected in serum. These findings have spurred speculations that mammalian extracellular RNAs bound to lipids and/or effector proteins might have biological functions following their uptake by target cells/tissues. Little, if any, experimental evidence presently supports this idea, however. Our laboratory has pioneered research on non-cell autonomous RNAi and was among the first to establish a link between RNA silencing, endo-membranes and vesicle trafficking in mammalian cells. Recently, we discovered that human and bovine milk contains physiological amounts of regulatory micro (mi)RNAs concentrated, notably, in milk fat globules (MFG), the source of fat for newborns. Moreover, we also detected high amounts of specific AGOs in MFG and other milk fractions, suggesting that AGO-bound miRNA, and perhaps other RNAs, might be functionally transferred into the new born gut epithelium and, perhaps distant organs, during feeding. Taking advantage of the formidable collection of mouse and cell-based genetic tools available from the McManus and Hunter laboratories, we propose here to use mammalian milk -an easily accessible and abundant body fluid- as a paradigm to investigate (i) the mechanisms underpinning miRNA secretion from the mammary gland, (ii) the protein and lipid environment of milk-contained miRNAs, including possibly novel milk-associated AGO partners, (iii) the mechanisms underpinning milk miRNA uptake by the gut epithelium, and (iv) if milk-borne miRNAs transferred from mother to pup during feeding effectively display biological activity in mouse newborns. Drawing from this knowledge and on clear precedents of trans-kingdom RNAi transfer between plants and parasitic invertebrates, we will finally address, using our unique plant-mammal dual expertise, if dietary RNA derived from crops can be functionally taken up by the gut epithelium of plant-fed mice.