Genetics of Cryptosporidium parvum

控制隐孢子虫毒力表型的基因是未知的，但需要对其进行鉴定，以指导药物的开发，更好地了解发病机制，并改善基因组的注释。本项目的目的是应用遗传方法绘制控制小孢子虫特定表型的基因图谱。与最初资助时期使用的连锁分析相比，我们建议采用连锁群选择，这是一种不需要克隆来自实验杂交的后代系的策略。相反，控制可选择性状的遗传位点是通过杂交两个表型不同的小孢子虫系，将未克隆的后代群体暴露在一轮或多轮选择压力下，并对大量后代群体进行定量基因分型来鉴定的。根据亲本系之间的表型差异，我们将选择卵囊的早期分化、卵囊对漂白剂的抗性和寄生虫对干扰素-？淘汰赛老鼠。在选择过程中，携带具有被选择的表型的等位基因的寄生虫将从后代中消除。由于减数分裂重组，来自敏感亲本的等位基因在选择位点附近的比例较低，形成“选择谷”。这样的谷将通过定量基因分型选定和控制的后代群体与一个面板的单核苷酸多态性确定。

Genes controlling virulence phenotypes in Cryptosporidium parasite are unknown, but their identification is needed to guide the development of drugs, to better understand pathogenesis, and to improve the annotation of the genome. The objective of this project is to apply genetic methods to map genes controlling specific phenotypes in C. parvum. In contrast to linkage analysis used in the initial funding period, we propose to apply Linkage Group Selection, a strategy which does not require the cloning of progeny lines derived from experimental crosses. Instead, genetic loci controlling selectable traits are identified by crossing two phenotypically distinct C. parvum lines, exposing uncloned progeny populations to one or multiple rounds of selective pressure, and quantitatively genotyping progeny populations in bulk. Based on phenotypic differences between the parental lines, we will select for early oocyst differentiation, oocyst resistance to bleach, and parasite infectivity to interferon-? knock-out mice. During selection, parasites carrying allele(s) conferring the phenotype selected against will be eliminated from the progeny. As a result of meiotic recombination, the proportion of alleles from the sensitive parent will be low in proximity to the locus under selection, creating a "selection valley". Such valleys will be identified by quantitatively genotyping a selected and a control progeny population with a panel of single nucleotide polymorphisms.