疟原虫伯氏疟原虫 Brca2 是小鼠和蚊子正常发育和分化所必需的。

Plasmodium berghei Brca2 is required for normal development and differentiation in mice and mosquitoes.

机构信息

Laboratory of Veterinary Biochemistry, School of Veterinary Medicine, Kitasato University, Towada, Aomori, 034-8628, Japan.

National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Inada, Obihiro, 080-8555, Japan.

出版信息

Parasit Vectors. 2022 Jul 8;15(1):244. doi: 10.1186/s13071-022-05357-w.

DOI:10.1186/s13071-022-05357-w

PMID:35804459

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC9270840/

Abstract

BACKGROUND

Malaria is a major global parasitic disease caused by species of the genus Plasmodium. Zygotes of Plasmodium spp. undergo meiosis and develop into tetraploid ookinetes, which differentiate into oocysts that undergo sporogony. Homologous recombination (HR) occurs during meiosis and introduces genetic variation. However, the mechanisms of HR in Plasmodium are unclear. In humans, the recombinases DNA repair protein Rad51 homolog 1 (Rad51) and DNA meiotic recombinase 1 (Dmc1) are required for HR and are regulated by breast cancer susceptibility protein 2 (BRCA2). Most eukaryotes harbor BRCA2 homologs. Nevertheless, these have not been reported for Plasmodium.

METHODS

A Brca2 candidate was salvaged from a database to identify Brca2 homologs in Plasmodium. To confirm that the candidate protein was Brca2, interaction activity between Plasmodium berghei (Pb) Brca2 (PbBrca2) and Rad51 (PbRad51) was investigated using a mammalian two-hybrid assay. To elucidate the functions of PbBrca2, PbBrca2 was knocked out and parasite proliferation and differentiation were assessed in mice and mosquitoes. Transmission electron microscopy was used to identify sporogony.

RESULTS

The candidate protein was conserved among Plasmodium species, and it was indicated that it harbors critical BRCA2 domains including BRC repeats, tower, and oligonucleotide/oligosaccharide-binding-fold domains. The P. berghei BRC repeats interacted with PbRad51. Hence, the candidate was considered a Brca2 homolog. PbBrca2 knockout parasites were associated with reduced parasitemia with increased ring stage and decreased trophozoite stage counts, gametocytemia, female gametocyte ratio, oocyst number, and ookinete development in both mice and mosquitoes. Nevertheless, the morphology of the blood stages in mice and the ookinete stage was comparable to those of the wild type parasites. Transmission electron microscopy results showed that sporogony never progressed in Brca2-knockout parasites.

CONCLUSIONS

Brca2 is implicated in nearly all Plasmodium life cycle stages, and especially in sporogony. PbBrca2 contributes to HR during meiosis.

摘要

背景

疟疾是一种由疟原虫属引起的主要全球性寄生虫病。疟原虫属的合子经历减数分裂并发育成四倍体卵囊，卵囊分化为孢囊，孢囊经历孢子发生。同源重组（HR）发生在减数分裂过程中，引入遗传变异。然而，疟原虫中的 HR 机制尚不清楚。在人类中，DNA 修复蛋白 RAD51 同源物 1（RAD51）和 DNA 减数分裂重组酶 1（DMC1）是 HR 所必需的，并且由乳腺癌易感性蛋白 2（BRCA2）调节。大多数真核生物都含有 BRCA2 同源物。然而，疟原虫中尚未报道过这些同源物。

方法

从数据库中抢救出一个 Brca2 候选物，以鉴定疟原虫中的 Brca2 同源物。为了确认候选蛋白是 Brca2，使用哺乳动物双杂交测定法研究了间日疟原虫（Pb）Brca2（PbBrca2）与 RAD51（PbRad51）之间的相互作用活性。为了阐明 PbBrca2 的功能，在小鼠和蚊子中敲除了 PbBrca2，并评估了寄生虫的增殖和分化。透射电子显微镜用于鉴定孢子发生。

结果

候选蛋白在疟原虫种间保守，表明它含有关键的 BRCA2 结构域，包括 BRC 重复、塔和寡核苷酸/寡糖结合折叠结构域。间日疟原虫的 BRC 重复与 PbRad51 相互作用。因此，该候选物被认为是 Brca2 同源物。PbBrca2 敲除寄生虫与寄生虫血症减少相关，环状阶段和滋养体阶段计数增加，配子血症、雌性配子体比例、卵囊数量和卵囊发育减少，在小鼠和蚊子中均如此。然而，小鼠的血期形态和卵囊阶段与野生型寄生虫相当。透射电子显微镜结果表明，孢子发生在 Brca2 敲除寄生虫中从未进展。