Trypanosoma cruzi is the etiologic agent of Chagas disease, and current methods for its genetic manipulation have been highly inefficient. We report here the use of the CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9 (CRISPR-associated gene 9) system for disrupting genes in the parasite by three different strategies. The utility of the method was established by silencing genes encoding the GP72 protein, which is required for flagellar attachment, and paraflagellar rod proteins 1 and 2 (PFR1, PFR2), key components of the parasite flagellum. We used either vectors containing single guide RNA (sgRNA) and Cas9, separately or together, or one vector containing sgRNA and Cas9 plus donor DNA for homologous recombination to rapidly generate mutant cell lines in which the PFR1, PFR2, and GP72 genes have been disrupted. We demonstrate that genome editing of these endogenous genes in T. cruzi is successful without detectable toxicity of Cas9. Our results indicate that PFR1, PFR2, and GP72 contribute to flagellar attachment to the cell body and motility of the parasites. Therefore, CRISPR/Cas9 allows efficient gene disruption in an almost genetically intractable parasite and suggest that this method will improve the functional analyses of its genome.

Trypanosoma cruzi is the agent of Chagas disease, and the finding that this parasite possesses a mitochondrial calcium uniporter (TcMCU) with characteristics similar to that of mammalian mitochondria was fundamental for the discovery of the molecular nature of MCU in eukaryotes. We report here that ablation of TcMCU, or its paralog TcMCUb, by clustered regularly interspaced short palindromic repeat (CRISPR)/Cas9 led to a marked decrease in mitochondrial Ca2+ uptake without affecting the membrane potential of these cells, whereas overexpression of each gene caused a significant increase in the ability of mitochondria to accumulate Ca2+. While TcMCU-knockout (KO) epimastigotes were viable and able to differentiate into trypomastigotes, infect host cells, and replicate normally, ablation of TcMCUb resulted in epimastigotes having an important growth defect, lower rates of respiration and metacyclogenesis, more pronounced autophagy changes under starvation, and significantly reduced infectivity. Overexpression of TcMCUb, in contrast to what was proposed for its mammalian ortholog, did not result in a dominant negative effect on TcMCU.

Background: Polyphosphate (polyP) accumulates in an acidic calcium store named the acidocalcisome. Results: TbVtc4 is an acidocalcisome polyP kinase required for osmoregulation and virulence. Conclusion: TbVtc4 is a potential drug target in T. brucei Significance: This is the first demonstration of an essential polyP kinase in trypanosomes.

Diverse microbial ecosystems underpin life in the sea. Among these microbes are many unicellular eukaryotes that span the diversity of the eukaryotic tree of life. However, genetic tractability has been limited to a few species, which do not represent eukaryotic diversity or environmentally relevant taxa. Here, we report on the development of genetic tools in a range of protists primarily from marine environments. We present evidence for foreign DNA delivery and expression in 13 species never before transformed and for advancement of tools for eight other species, as well as potential reasons for why transformation of yet another 17 species tested was not achieved. Our resource in genetic manipulation will provide insights into the ancestral eukaryotic lifeforms, general eukaryote cell biology, protein diversification and the evolution of cellular pathways.

Edited by Dennis VoelkerMethods for genetic manipulation of Trypanosoma cruzi, the etiologic agent of Chagas disease, have been highly inefficient, and no endogenous tagging of genes has been reported to date. We report here the use of the CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9 (CRISPR-associated gene 9) system for endogenously tagging genes in this parasite. The utility of the method was established by tagging genes encoding proteins of known localization such as TcFCaBP (flagellar calcium binding protein) and TcVP1 (vacuolar proton pyrophosphatase), and two proteins of undefined or disputed localization, the TcMCU (mitochondrial calcium uniporter) and TcIP 3 R (inositol 1,4,5-trisphosphate receptor). We confirmed the flagellar and acidocalcisome localization of TcFCaBP and TcVP1 by co-localization with antibodies to the flagellum and acidocalcisomes, respectively. As expected, TcMCU was colocalized with the voltage-dependent anion channel to the mitochondria. However, in contrast to previous reports and our own results using overexpressed TcIP 3 R, endogenously tagged TcIP 3 R showed co-localization with antibodies against VP1 to acidocalcisomes. These results are also in agreement with our previous reports on the localization of this channel to acidocalcisomes of Trypanosoma brucei and suggest that caution should be exercised when overexpression of tagged genes is done to localize proteins in T. cruzi.The application of the CRISPR/Cas9 technology to the study of protist parasites has dramatically increased the tools available for their genetic manipulation (1). Trypanosoma cruzi, the etiologic agent of Chagas disease, which is a significant cause of morbidity and mortality from the South of the United States to the South of Argentina and Chile, has been particularly refractory to genetic manipulation. However, the recent use of the CRISPR/Cas9 technology to knock down or knock out genes (2, 3) has revolutionized their study.The localization of proteins is important to determine their cellular function, and previous studies in T. cruzi have used either antibodies or gene tagging methods with vectors that overexpressed the proteins (4). Although specific antibodies are useful to detect the endogenous proteins, it is not always possible to obtain them because either the proteins have low antigenicity or the antibodies cross-react with other proteins. Plasmids that enable the tagging of genes at their endogenous loci are not available for T. cruzi, and a major drawback of the overexpression of tagged proteins is that the proteins of interest sometimes are retained in the endoplasmic reticulum (ER) 4 or localize to other compartments.Here we have adapted the CRISPR/Cas9 system to tag genes of T. cruzi at their endogenous loci and tested this system with two genes encoding proteins of well recognized localization (flagellar calcium binding protein or TcFCaBP and the acidocalcisome vacuolar proton pyrophosphatase or TcVP1) and two encoding proteins of undefined or disputed localizati...

While free-living protists are usually subjected to hyposmotic environments, parasitic protists are also in contact with hyperosmotic habitats. Recent work in one of these parasites, Trypanosoma cruzi, has revealed that its contractile vacuole complex, which usually collects and expels excess water as a mechanism of regulatory volume decrease after hyposmotic stress, has also a role in cell shrinking when the cells are submitted to hyperosmotic stress. Trypanosomes also have an acidic calcium store rich in polyphosphate (polyP), named the acidocalcisome, which is involved in their response to osmotic stress. Here, we review newly emerging insights on the role of acidocalcisomes and the contractile vacuole complex in the cellular response to hyposmotic and hyperosmotic stresses. We also review the current state of knowledge on the composition of these organelles and their other roles in calcium homeostasis and protein trafficking.

Statins are efficient cholesterol-lowering medicines utilized worldwide. However, 10% of patients suffer from adverse effects specially related to skeletal muscle function. Pro- or anti-oxidant effects of statins have been reported. Here we hypothesized that statins induce muscle mitochondrial oxidative stress leading to mitochondrial permeability transition (MPT) which may explain statin muscle toxicity. Thus, our aims were to investigate the effects of statin chronic treatment on muscle mitochondrial respiration rates, MPT and redox state indicators in the context of hypercholesterolemia. For this purpose, we studied muscle biopsies of the hypercholesterolemic LDL receptor knockout mice (LDLr-/-) treated with pravastatin during 3 months. Plantaris, but not soleus muscle of treated mice showed significant inhibition of respiration rates induced by ADP (–14%), oligomycin (–20%) or FCCP (–40%). Inhibitions of respiratory rates were sensitive to EGTA (Ca2+ chelator), cyclosporin A (MPT inhibitor), ruthenium red (inhibitor of mitochondria Ca2+ uptake) and coenzyme Q10 (antioxidant), indicating that pravastatin treatment favors Ca2+ induced MPT. Diet supplementation with creatine (antioxidant) also protected treated mice against pravastatin sensitization to Ca2+ induced MPT. Among several antioxidant enzymes analyzed, only catalase activity was increased by 30% in plantaris muscle of pravastatin treated mice. Oxidized lipids, but not proteins biomarkers were identified in treated LDLr-/- plantaris muscle. Taken together, the present results suggest that chronic pravastatin administration to a model of familial hypercholesterolemia promotes mitochondrial dysfunctions in plantaris muscle that can be counteracted by antioxidants administered either in vitro (CoQ10) or in vivo (creatine). Therefore, we propose that inhibition of muscle mitochondrial respiration by pravastatin leads to an oxidative stress that, in the presence of calcium, opens the permeability transition pore. This mitochondrial oxidative stress caused by statin treatment also signals for cellular antioxidant system responses such as catalase upregulation. These results suggest that the detrimental effects of statins on muscle mitochondria could be prevented by co-administration of a safe antioxidant such as creatine or CoQ10.

Inorganic polyphosphate (polyP) accumulates in acidocalcisomes, acidic calcium stores that have been found from bacteria to human cells. Proton pumps, such as the vacuolar proton pyrophosphatase (V-H+-PPase, or VP1), the vacuolar proton ATPase (V-H+-ATPase), or both, maintain their acidity. A vacuolar transporter chaperone complex (VTC) is involved in the synthesis and translocation of polyP to these organelles in several eukaryotes, such as yeast, trypanosomatids, Apicomplexan, and algae. Studies in trypanosomatids have revealed the role of polyP and acidocalcisomes in osmoregulation and calcium signaling.