Genetics of Cryptosporidium parvum

描述（由申请人提供）：隐孢子虫感染艾滋病患者和其他免疫缺陷个体，是儿童腹泻的常见原因。对人类志愿者和动物的研究表明，分离株之间的毒力存在明显差异，但毒力的遗传决定因素尚不清楚。本文介绍了本实验室最近发展的一种用C.小鼠体内的细小病毒株为利用遗传学方法研究这种病原体开辟了新的可能性。我们发现C.在混合小鼠感染中产生具有重组基因型的细小病毒株系，并且不同基因型之间的重组可产生高毒性子代株系。由于在实验杂交中获得了具有不同毒力特性的多个重组系，因此可以使用连锁分析来鉴定毒力的遗传决定因素，而无需事先了解毒力决定因素。我们的中心假设是，大多数临床或生物学相关的表型特性在C。矮生性状是由多基因控制的数量性状，可以通过连锁分析进行鉴定。具体目标：1。建立了一张高密度的C. 2型。几乎完成的C。基因组序列将有助于多态性微卫星，限制性片段长度多态性和单核苷酸多态性的鉴定。2.确定交配结构和遗传的染色体外元件在基因型混合C。细小病毒感染我们将测试工作假设，在混合C。寄生虫感染受精是相同或不同配子随机融合的结果，自交与异交的比例符合随机交配模型。将在这一特定目标的背景下研究病毒RNA基因组的遗传。3.鉴定2C型的毒力标记.利用数量性状基因座（QTL）分析，研究了矮生菜豆的遗传多样性。这一目标是基于初步观察，C。parvum lines产生具有不同杀死小鼠能力的后代。我们将测试以下两个工作假设：a）毒力是由多个遗传位点决定的。B）QTL分析可用于鉴定与毒力相关的基因组区段。

DESCRIPTION (provided by applicant): Cryptosporidium parvum infects AIDS patients and other immunodeficient individuals and is a frequent cause of childhood diarrhea. Studies in human volunteers and animals have revealed pronounced differences in virulence among isolates, but the genetic determinants of virulence are unknown. The recent development in our laboratory of a method to cross C. parvum lines in mice opens new possibilitiesfor studying this pathogen using genetic methods. We have found that C. parvum lines with recombinant genotypes are produced in mixed mouse infections and that recombination between different genotypes can produce highly virulent progeny lines. Since multiple recombinant lines with different virulence properties are obtained in experimental crosses, linkage analysis can be used to identify genetic determinants of virulence, without prior knowledge of virulence determinants. It is our central hypothesis that a majority of clinically or biologically relevant phenotypic properties in C. parvum are quantitative traits controlled by multiple genes which can be identified by linkage analysis. Specific Aims: 1. Establish a high-density map of polymorphic genetic markers for C. parvum type 2. The almost completed C. parvum genome sequence will facilitate the identification of polymorphic microsatellites, restriction fragment length polymorphisms and single nucleotide polymorphisms. 2. Determine the mating structure and the inheritance of an extrachromosomal element in genotypically mixed C. parvum infections. We will test the working hypothesis that in mixed C. parvum infections fertilization results from the random fusion of identical or dissimilar gametes, and that the ratio of self- to cross-mating conforms to the model of random mating. The inheritance of a viral RNA genome will be studied in the context of this specific aim. 3. Identify virulence markers in type 2 C. parvum using Quantitative Trait Locus (QTL) analysis. This aim is based on preliminary observations that recombination between C. parvum lines generates progeny with distinct capacities to kill mice. We will test the following two working hypotheses: a) Virulence is determined by multiple genetic loci. b) QTL analysis can be used to identify genomic segments associated with virulence.