Sexual Development of Toxoplasma in Feline Intestinal Organoids

弓形虫的性周期仅限于猫的肠道，在那里形成数百万个卵囊，然后从它们的粪便中排出。我们之前的R21的目标是在组织培养中概括弓形虫的有性周期。我们通过与密歇根大学的Jason Spence合作生产猫肠道有机化合物，并用饱和脂肪酸补充感染弓形虫的有机化合物，实现了这一目标，导致我们假设饱和脂肪酸被用作信号分子，而不是营养。多不饱和脂肪酸通常被加工成信号分子，通过脂氧合酶作用使其双键氧化。弓形虫基因组编码四种脂氧合酶，其中一种被称为TgLOX1的TGME49_315970在猫肠道中的表达是无性阶段的600倍。我们推测TgLOX1氧化亚油酸是性发育的信号。R01的目标之一就是验证这一假设。R01的另一个目标是测试3D培养和低氧条件将最大限度地提高卵囊产量的假设。虽然我们可以产生对小鼠具有感染力的孢子化卵囊，但总体产量很低，因为培养物中的大多数卵囊不产生孢子。目前，我们将猫科动物的肠道细胞放在Snapwell插入物上，这样肠的顶端很容易受到感染，但这些细胞是2D的，这可能会影响弓形虫的发育。为了建立3D肠道模型，我们将在R01中测试两种方法，1)全肠道器官的显微注射，2)创建肠道管的简单生物医学工程设备。这些新的3D模型以及降低氧气浓度将更接近地模拟猫的小肠，并可能产生更成熟的卵囊，以更高的效率产孢子。R01的最终目标是确定弓形虫性别发育的物种特异性。弓形虫的有性周期仅限于猫，但原因尚不清楚。总体而言，创造细胞培养的性发育条件将使经典的遗传杂交成为弓形虫领域的常规技术。它还将允许对原生动物寄生虫的完整生命周期进行分子分析，因为弓形虫的无性发育已经可以在组织培养中进行。

The sexual cycle of Toxoplasma gondii is limited to the feline intestine where millions of oocysts are formed and subsequently excreted in their feces. The goal of our previous R21 was to recapitulate the T. gondii sexual cycle in tissue culture. We achieved this goal by generating cat intestinal organoids in collaboration with Jason Spence at the University of Michigan and supplementing the T. gondii infected organoids with saturated fatty acids, leading us to hypothesize that saturated fatty acids are used as a signaling molecules and not for nutrition. Polyunsaturated fatty acids are often processed to signaling molecules by oxygenation of their double bonds through the action of lipoxygenases. The T. gondii genome encodes four lipoxygenases, one of which, annotation TGME49_315970 called TgLOX1, is 600-fold upregulated in cat intestine compared to asexual stages. We hypothesize that TgLOX1 oxygenates linoleic acid to signal sexual development. One of the goals of this R01 is to test this hypothesis. Another goal of this R01 is to test the hypothesis that 3D culture and low oxygen conditions will maximize oocyst production. While we can generate sporulated oocysts that are infectious to mice, the overall yield is low because most of the oocysts in the culture do not sporulate. Currently, we plate our feline intestinal cells on snapwell inserts so that the apical side of the intestine is easy to infect, but the cells are in 2D, which may affect T. gondii development. To model 3D intestines, we will test two methods in this R01, 1) microinjection of the whole intestinal organoid, 2) a simple biomedical engineering device that creates intestinal tubes. These new 3D models as well as lowering the oxygen concentration will more closely model the cat small intestine and likely produce more mature oocysts that sporulate with greater efficiency. The final goal for this R01 is to determine the species specificity for T. gondii sexual development. The sexual cycle of T. gondii is restricted to the cat, but it is unclear why. Overall, creation of cell culture sexual development conditions will allow classical genetic crosses to become a routine technique for the T. gondii field. It will also allow for a molecular analysis of the complete life cycle of a protozoan parasite, as T. gondii asexual development can already be performed in tissue culture.