Molecular Basis of Intestinal Cryptosporidiosis

 描述(申请人提供)：隐孢子虫是一种普遍存在的病原体，感染人类的胃肠道上皮。这种寄生虫在医学上非常重要，因为免疫受损的人类感染，包括艾滋病、癌症和移植患者，往往会导致危及生命的疾病。隐孢子虫也是发展中国家幼儿腹泻的常见原因。目前还没有完全有效的治疗方法 感染。目前对寄生虫生物学和寄生虫-宿主相互作用的分子机制的了解有限。在我们的初步研究中，我们对隐孢子虫非编码RNA(NcRNAs)进入感染宿主细胞的细胞核进行了新的观察。我们的结果还表明，隐孢子虫感染抑制了一组基因的转录，这些基因编码对肠上皮细胞分化和新陈代谢至关重要的效应蛋白。 重要的是，这个基因组的反式抑制与抑制表观遗传标记(如H3K9me3)在其基因座上的浓缩有关，涉及寄生虫ncRNAs的核存在。因此，我们将验证隐孢子虫感染通过特定寄生虫ncRNAs的核传递在宿主细胞中诱导表观遗传组蛋白甲基化，从而导致宿主中具有病理效应的基因转录抑制的假说。利用遗传学方法和前沿技术，我们将确定寄生虫ncRNA在受感染宿主细胞中的核传递机制(目标1)，阐明感染如何诱导抑制H3K9甲基化的丰富，从而导致受感染的上皮细胞中基因的反式抑制(目标2)，并确定寄生虫ncRNA在核传递中的作用。 通过评估隐孢子虫病对宿主细胞组蛋白甲基化的染色质浓缩的影响来研究隐孢子虫病的发病机制(目标3)。这项研究的结果将揭示关于寄生虫-宿主相互作用的有价值的信息，并使未来旨在阻断特定转录事件作为治疗这种感染的新方法的研究成为可能。

 DESCRIPTION (provided by applicant): Cryptosporidium is a ubiquitous pathogen that infects the gastrointestinal epithelium in humans. This parasite is of great medical importance as infections in immunocompromised humans, including AIDS, cancer, and transplant patients, often lead to life-threatening illness. Cryptosporidium is also a common cause of diarrhea in young children in developing countries. There is currently no fully effective therapy available for the infection. Current understanding of the parasite biology and the molecular mechanisms of parasite-host interactions is limited. In our preliminary study, we made a novel observation on the delivery of Cryptosporidium non-coding RNAs (ncRNAs) into the nuclei of infected host cells. Our results also show that cryptosporidial infection suppresses transcription of a panel of genes that code effector proteins key to intestinal epithelial cell differentiation and metabolism. Importantly, transsuppression of this gene panel is associated with enrichment of suppressive epigenetic markers (e.g., H3K9me3) to their gene loci with the involvement of nuclear presence of parasite ncRNAs. Therefore, we will test the hypothesis that cryptosporidial infection induces epigenetic histone methylations in host cells through nuclear delivery of specific parasite ncRNAs, resulting in transcriptional suppression of genes with pathological effects in the host. Using genetic approaches and cutting-edge technologies, we will determine the mechanisms of nuclear delivery of parasite ncRNAs in infected host cells (Aim 1), elucidate how infection induces enrichment of suppressive H3K9 methylation, resulting in transrepression of genes in infected epithelial cells (Aim 2), and determine the role of parasite ncRNA nuclear delivery in the pathogenesis of cryptosporidiosis by assessing its impact on chromatin enrichment of histone methylations in host cells (Aim 3). The results of this study will reveal valuable information abou parasite-host interactions and make possible future investigations aimed at blocking specific transcriptional events as a novel treatment for the infection.