Characterization of the novel mitochondrial genome segregation factor TAP110 in Trypanosoma brucei

A new member of the dynamin superfamily modulates mitochondrial membrane branching in Trypanosoma brucei

Unlike most other eukaryotes, where mitochondria continuously fuse and divide, the mitochondrion of trypanosome cells forms a single and continuously interconnected network that divides only during cytokinesis. However, the machinery governing mitochondrial remodeling and interconnection of trypanosome mitochondrion remain largely unknown. We functionally characterize a new member of the dynamin superfamily protein (DSP) from T. brucei (TbMfnL), which shares similarity with a family of homologs present in various eukaryotic and prokaryotic phyla but not in opisthokonts like mammals and budding yeast. The sequence and domain organization of TbMfnL is distinct, and it is phylogenetically very distant from the yeast and mammalian dynamin-related proteins involved in mitochondrial fusion/fission dynamics, such as optic atrophy 1 (Opa1) and mitofusin (Mfn). TbMfnL localizes to the inner mitochondrial membrane facing the matrix and, upon overexpression, induces a strong increase in the interconnection and branching of mitochondrial filaments in a GTPase-dependent manner. TbMfnL is a component of a novel membrane remodeling machinery with an unprecedented matrix-side localization that is able to modulate the degree of inter-mitochondrial connections.

Ultrastructure expansion microscopy: Enlarging our perspective on apicomplexan cell division

Apicomplexans, a large phylum of protozoan intracellular parasites, well known for their ability to invade and proliferate within host cells, cause diseases with major health and economic impacts worldwide. These parasites are responsible for conditions such as malaria, cryptosporidiosis, and toxoplasmosis, which affect humans and other animals. Apicomplexans exhibit complex life cycles, marked by diverse modes of cell division, which are closely associated with their pathogenesis. All the unique structural and evolutionary characteristics of apicomplexan parasites, the biology underlying life stage transitions, and the singular mechanisms of cell division alongside their associated biomedical relevance have captured the attention of parasitologists of all times. Traditional light and electron microscopy have set the fundamental foundations of our understanding of these parasites, including the distinction among their modes of cell division. This has been more recently complemented by microscopy advances through the implementation of superresolution fluorescence microscopy, and variants of electron microscopy, such as cryo-EM and tomography, revealing intricate details of organelles and cell division. Ultrastructure Expansion Microscopy has emerged as a transformative, accessible approach that enhances resolution by physically expanding samples isometrically, allowing nanoscale visualisation on standard light microscopes. In this work, we review the most recent contributions of U-ExM and its recent improvements and innovations, in providing unprecedented insights into apicomplexan ultrastructure and its associated mechanisms, focusing particularly on cell division. We highlight the power of U-ExM in combination with protein-specific labelling, in aiding the visualisation of long oversighted organelles and detailed insights into the assembly of parasite-specific structures, such as the conoid in Plasmodia, and the apical-basal axis in Toxoplasma, respectively, during new parasite assembly. Altogether, the contributions of U-ExM reveal conserved and unique structural features across species while nearing super resolution. The development of these methodologies and their combination with different technologies are crucial for advancing our mechanistic understanding of apicomplexan biology, offering new perspectives that may facilitate novel therapeutic strategies against apicomplexan-caused diseases.

Kinetoplast DNA: a polymer physicist's topological Olympic dream

All life forms are miraculous, but some are more inexplicable than others. Trypanosomes are by far one of the most puzzling organisms on Earth: their mitochondrial genome, also called kinetoplast DNA (kDNA) forms an Olympic-ring-like network of interlinked DNA circles, challenging conventional paradigms in both biology and physics. In this review, I will discuss kDNA from the astonished perspective of a polymer physicist and tell a story of how a single sub-cellular structure from a blood-dwelling parasite is inspiring generations of polymer chemists and physicists to create new catenated materials.

A novel nabelschnur protein regulates segregation of the kinetoplast DNA in Trypanosoma brucei

The acquisition of mitochondria was imperative for initiating eukaryogenesis and thus is a characteristic feature of eukaryotic cells.1,2 The parasitic protist Trypanosoma brucei contains a singular mitochondrion with a unique mitochondrial genome, termed the kinetoplast DNA (kDNA).3 Replication of the kDNA occurs during the G1 phase of the cell cycle, prior to the start of nuclear DNA replication.4 Although numerous proteins have been functionally characterized and identified as vital components of kDNA replication and division, the molecular mechanisms governing this highly precise process remain largely unknown.5,6 One division-related and morphologically characteristic structure that remains most enigmatic is the "nabelschnur," an undefined, filament-resembling structure observed by electron microscopy between segregating daughter kDNA networks.7,8,9 To date, only one protein, TbLAP1, an M17 family leucyl aminopeptidase metalloprotease, is known to localize to the nabelschnur.9 While screening proteins from the T. brucei MitoTag project,10 we identified a previously uncharacterized protein with an mNeonGreen signal localizing to the kDNA as well as forming a point of connection between dividing kDNAs. Here, we demonstrate that this kDNA-associated protein, named TbNAB70, indeed localizes to the nabelschnur and plays an essential role in the segregation of newly replicated kDNAs and subsequent cytokinesis in T. brucei.

High-throughput prioritization of target proteins for development of new antileishmanial compounds

Leishmaniasis, a vector-borne disease, is caused by the infection of Leishmania spp., obligate intracellular protozoan parasites. Presently, human vaccines are unavailable, and the primary treatment relies heavily on systemic drugs, often presenting with suboptimal formulations and substantial toxicity, making new drugs a high priority for LMIC countries burdened by the disease, but a low priority in the agenda of most pharmaceutical companies due to unattractive profit margins. New ways to accelerate the discovery of new, or the repositioning of existing drugs, are needed. To address this challenge, our study aimed to identify potential protein targets shared among clinically-relevant Leishmania species. We employed a subtractive proteomics and comparative genomics approach, integrating high-throughput multi-omics data to classify these targets based on different druggability metrics. This effort resulted in the ranking of 6502 ortholog groups of protein targets across 14 pathogenic Leishmania species. Among the top 20 highly ranked groups, metabolic processes known to be attractive drug targets, including the ubiquitination pathway, aminoacyl-tRNA synthetases, and purine synthesis, were rediscovered. Additionally, we unveiled novel promising targets such as the nicotinate phosphoribosyltransferase enzyme and dihydrolipoamide succinyltransferases. These groups exhibited appealing druggability features, including less than 40% sequence identity to the human host proteome, predicted essentiality, structural classification as highly druggable or druggable, and expression levels above the 50th percentile in the amastigote form. The resources presented in this work also represent a comprehensive collection of integrated data regarding trypanosomatid biology.

Expansion of metabolically labelled endocytic organelles and cytoskeletal cell structures in Giardia lamblia using optimised U-ExM protocols

Understanding cellular ultrastructure is tightly bound to microscopic resolution and the ability to identify individual components at that resolution. Expansion microscopy has revolutionised this topic. Here we present and compare two protocols of ultrastructure expansion microscopy that allow for 4.5-fold mostly isotropic expansion and the use of antibodies, metabolic labelling, and DNA stains to demarcate individual regions such as the endoplasmic reticulum, the nuclei, the peripheral endocytic compartments as well as the ventral disc and the cytoskeleton in Giardia lamblia. We present an optimised, shortened, and modular protocol that can be swiftly adjusted to the investigators needs in this important protozoan model organism.

Continuous endosomes form functional subdomains and orchestrate rapid membrane trafficking in trypanosomes

Endocytosis is a common process observed in most eukaryotic cells, although its complexity varies among different organisms. In Trypanosoma brucei, the endocytic machinery is under special selective pressure because rapid membrane recycling is essential for immune evasion. This unicellular parasite effectively removes host antibodies from its cell surface through hydrodynamic drag and fast endocytic internalization. The entire process of membrane recycling occurs exclusively through the flagellar pocket, an extracellular organelle situated at the posterior pole of the spindle-shaped cell. The high-speed dynamics of membrane flux in trypanosomes do not seem compatible with the conventional concept of distinct compartments for early endosomes (EE), late endosomes (LE), and recycling endosomes (RE). To investigate the underlying structural basis for the remarkably fast membrane traffic in trypanosomes, we employed advanced techniques in light and electron microscopy to examine the three-dimensional architecture of the endosomal system. Our findings reveal that the endosomal system in trypanosomes exhibits a remarkably intricate structure. Instead of being compartmentalized, it constitutes a continuous membrane system, with specific functions of the endosome segregated into membrane subdomains enriched with classical markers for EE, LE, and RE. These membrane subdomains can partly overlap or are interspersed with areas that are negative for endosomal markers. This continuous endosome allows fast membrane flux by facilitated diffusion that is not slowed by multiple fission and fusion events.

Microtubule polyglutamylation is an essential regulator of cytoskeletal integrity in Trypanosoma brucei

Tubulin polyglutamylation, catalysed by members of the tubulin tyrosine ligase-like (TTLL) protein family, is an evolutionarily highly conserved mechanism involved in the regulation of microtubule dynamics and function in eukaryotes. In the protozoan parasite Trypanosoma brucei, the microtubule cytoskeleton is essential for cell motility and maintaining cell shape. In a previous study, we showed that T. brucei TTLL6A and TTLL12B are required to regulate microtubule dynamics at the posterior cell pole. Here, using gene deletion, we show that the polyglutamylase TTLL1 is essential for the integrity of the highly organised microtubule structure at the cell pole, with a phenotype distinct from that observed in TTLL6A- and TTLL12B-depleted cells. Reduced polyglutamylation in TTLL1-deficient cells also leads to increased levels in tubulin tyrosination, providing new evidence for an interplay between the tubulin tyrosination and detyrosination cycle and polyglutamylation. We also show that TTLL1 acts differentially on specific microtubule doublets of the flagellar axoneme, although the absence of TTLL1 appears to have no measurable effect on cell motility.

Expansion Microscopy of trichomonads

Light microscopy has significantly advanced in recent decades, especially concerning the increased resolution obtained in fluorescence images. Here we present the Expansion Microscopy (ExM) technique in two parasites, Trichomonas vaginalis and Tritrichomonas foetus, which significantly improved the localization of distinct proteins closely associated with cytoskeleton by immunofluorescence microscopy. The ExM techniques have been used in various cell types, tissues and other protist parasites. It requires the embedment of the samples in a swellable gel that is highly hydrophilic. As a result, cells are expanded 4.5 times in an isotropic manner, offering a spatial resolution of ∼70 nm. We used this new methodology not only to observe the structural organization of protozoa in more detail but also to increase the resolution by immunofluorescence microscopy of two major proteins such as tubulin, found in structures formed by microtubules, and costain 1, the only protein identified until now in the T. foetus's costa, a unique rod-shaped like structure. The individualized microtubules of the axostyle were seen for the first time in fluorescence microscopy and several other details are presented after this technique.

Characterization of two novel proteins involved in mitochondrial DNA anchoring in Trypanosoma brucei

Trypanosoma brucei is a single celled eukaryotic parasite in the group of the Kinetoplastea. The parasite harbors a single mitochondrion with a singular mitochondrial genome that is known as the kinetoplast DNA (kDNA). The kDNA consists of a unique network of thousands of interlocked circular DNA molecules. To ensure proper inheritance of the kDNA to the daughter cells, the genome is physically linked to the basal body, the master organizer of the cell cycle in trypanosomes. The connection that spans, cytoplasm, mitochondrial membranes and the mitochondrial matrix is mediated by the Tripartite Attachment Complex (TAC). Using a combination of proteomics and RNAi we test the current model of hierarchical TAC assembly and identify TbmtHMG44 and TbKAP68 as novel candidates of a complex that connects the TAC to the kDNA. Depletion of TbmtHMG44 or TbKAP68 each leads to a strong kDNA loss but not missegregation phenotype as previously defined for TAC components. We demonstrate that the proteins rely on both the TAC and the kDNA for stable localization to the interface between these two structures. In vitro experiments suggest a direct interaction between TbmtHMG44 and TbKAP68 and that recombinant TbKAP68 is a DNA binding protein. We thus propose that TbmtHMG44 and TbKAP68 are part of a distinct complex connecting the kDNA to the TAC.

[Closer to the native architecture of the cell using Cryo-ExM]

Most cellular imaging techniques, such as light or electron microscopy, require that the biological sample is first fixed by chemical cross-linking agents. This necessary step is also known to damage molecular nanostructures or even sub-cellular organization. To overcome this problem, another fixation approach was invented more than 40 years ago, which consists in cryo-fixing biological samples, thus allowing to preserve their native state. However, this method has been scarcely used in light microscopy due to the complexity of its implementation. In this review, we present a recently developed super-resolution method called expansion microscopy, which, when coupled with cryo-fixation, allows to visualize at a nanometric resolution the cell architecture as close as possible to its native state.

Ultrastructure expansion microscopy reveals the cellular architecture of budding and fission yeast

The budding and fission yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe have served as invaluable model organisms to study conserved fundamental cellular processes. Although super-resolution microscopy has in recent years paved the way to a better understanding of the spatial organization of molecules in cells, its wide use in yeasts has remained limited due to the specific know-how and instrumentation required, contrasted with the relative ease of endogenous tagging and live-cell fluorescence microscopy. To facilitate super-resolution microscopy in yeasts, we have extended the ultrastructure expansion microscopy (U-ExM) method to both S. cerevisiae and S. pombe, enabling a 4-fold isotropic expansion. We demonstrate that U-ExM allows imaging of the microtubule cytoskeleton and its associated spindle pole body, notably unveiling the Sfi1p–Cdc31p spatial organization on the appendage bridge structure. In S. pombe, we validate the method by monitoring the homeostatic regulation of nuclear pore complex number through the cell cycle. Combined with NHS-ester pan-labelling, which provides a global cellular context, U-ExM reveals the subcellular organization of these two yeast models and provides a powerful new method to augment the already extensive yeast toolbox.

This article has an associated First Person interview with Kerstin Hinterndorfer and Felix Mikus, two of the joint first authors of the paper.

Single p197 molecules of the mitochondrial genome segregation system of Trypanosoma brucei determine the distance between basal body and outer membrane

Segregation of the replicated single unit mitochondrial genome of Trypanosoma brucei requires a large hardwired structure that connects the organellar DNA with the flagellar basal body. The cytosolic part of this structure consists of filaments made of p197 molecules, a protein with a molecular weight of approximately 660 kDa. The N terminus of p197 is anchored to the peripheral mitochondrial outer membrane protein TAC65, whereas its C terminus connects to the base of the basal body. The large α-helical central domain of p197 consists of approximately 26 repeats each 175 aa in length. It provides a flexible spacer that connects the outer membrane with the basal body and determines the distance between the two structures.

The tripartite attachment complex (TAC) couples the segregation of the single unit mitochondrial DNA of trypanosomes with the basal body (BB) of the flagellum. Here, we studied the architecture of the exclusion zone filament (EZF) of the TAC, the only known component of which is p197, that connects the BB with the mitochondrial outer membrane (OM). We show that p197 has three domains that are all essential for mitochondrial DNA inheritance. The C terminus of p197 interacts with the mature and probasal body (pro-BB), whereas its N terminus binds to the peripheral OM protein TAC65. The large central region of p197 has a high α-helical content and likely acts as a flexible spacer. Ultrastructure expansion microscopy (U-ExM) of cell lines exclusively expressing p197 versions of different lengths that contain both N- and C-terminal epitope tags demonstrates that full-length p197 alone can bridge the ∼270-nm distance between the BB and the cytosolic face of the OM. Thus U-ExM allows the localization of distinct domains within the same molecules and suggests that p197 is the TAC subunit most proximal to the BB. In addition, U-ExM revealed that p197 acts as a spacer molecule, as two shorter versions of p197, with the repeat domain either removed or replaced by the central domain of the Trypanosoma cruzi p197 ortholog reduced the distance between the BB and the OM in proportion to their predicted molecular weight.

Ultrastructure Expansion Microscopy (U-ExM) in Trypanosoma cruzi: localization of tubulin isoforms and isotypes

Ultrastructure Expansion Microscopy (U-ExM) is a recently developed technique that enables the increase of the spatial resolution within a cell or a tissue for microscopic imaging by physically expanding the sample. For the first time, I report a detailed protocol validating the use of U-ExM in Trypanosoma cruzi and quantifying the expansion factors of different subcellular compartments. I was able to determine the localization patterns of different tubulin isoforms, such as α-tubulin and β-tubulin. Also, I immunolocalized acetylated and tyrosinated α-tubulin isotypes in epimastigotes and use mitochondrial cell-permeable dyes to identify this organelle. Finally, U-ExM was also performed in trypomastigotes and amastigotes validating this technique in all life cycle stages of T. cruzi.

Kinetoplastid-specific X2-family kinesins interact with a kinesin-like pleckstrin homology domain protein that localizes to the trypanosomal microtubule quartet

Kinesins are motor proteins found in all eukaryotic lineages that move along microtubules to mediate cellular processes such as mitosis and intracellular transport. In trypanosomatids, the kinesin superfamily has undergone a prominent expansion, resulting in one of the most diverse kinesin repertoires that includes the two kinetoplastid-restricted families X1 and X2. Here, we characterize in Trypanosoma brucei TbKifX2A, an orphaned X2 kinesin. TbKifX2A tightly interacts with TbPH1, a kinesin-like protein with a likely inactive motor domain, a rarely reported occurrence. Both TbKifX2A and TbPH1 localize to the microtubule quartet (MtQ), a characteristic but poorly understood cytoskeletal structure that wraps around the flagellar pocket as it extends to the cell body anterior. The proximal proteome of TbPH1 revealed two other interacting proteins, the flagellar pocket protein FP45 and intriguingly another X2 kinesin, TbKifX2C. Simultaneous ablation of TbKifX2A/TbPH1 results in the depletion of FP45 and TbKifX2C and also an expansion of the flagellar pocket, among other morphological defects. TbKifX2A is the first motor protein to be localized to the MtQ. The observation that TbKifX2C also associates with the MtQ suggests that the X2 kinesin family may have co-evolved with the MtQ, both kinetoplastid-specific traits.

Paving the Way: Contributions of Big Data to Apicomplexan and Kinetoplastid Research

In the age of big data an important question is how to ensure we make the most out of the resources we generate. In this review, we discuss the major methods used in Apicomplexan and Kinetoplastid research to produce big datasets and advance our understanding of Plasmodium, Toxoplasma, Cryptosporidium, Trypanosoma and Leishmania biology. We debate the benefits and limitations of the current technologies, and propose future advancements that may be key to improving our use of these techniques. Finally, we consider the difficulties the field faces when trying to make the most of the abundance of data that has already been, and will continue to be, generated.

TFK1, a basal body transition fibre protein that is essential for cytokinesis in Trypanosoma brucei

In Trypanosoma brucei, transition fibres (TF) form a nine-bladed pattern-like structure connecting the base of the flagellum to the flagellar pocket membrane. Despite the characterization of two TF proteins, CEP164C and TbRP2, little is known about the organization of these fibres. Here, we report the identification and characterization of the first kinetoplastid-specific TF protein named TFK1 (Tb927.6.1180). Bioinformatics and functional domain analysis identified three TFK1 distinct domains: an N-terminal domain of an unpredicted function, a coiled-coil domain involved in TFK1-TFK1 interaction and a C-terminal intrinsically disordered region potentially involved in protein interaction. Cellular immuno-localization showed that TFK1 is a newly identified basal body maturation marker. Further, using ultrastructure expansion and immuno-electron microscopies we localized CEP164C and TbRP2 at the TF and TFK1 on the distal appendage matrix of the TF. Importantly, RNAi knockdown of TFK1 in bloodstream form cells induced misplacement of basal bodies, a defect in the furrow or fold generation and eventually cell death. We hypothesize that TFK1 is a basal body positioning specific actor and a key regulator of cytokinesis in the bloodstream form Trypanosoma brucei.

Ultrastructure expansion microscopy in Trypanosoma brucei

The recently developed ultrastructure expansion microscopy (U-ExM) technique allows us to increase the spatial resolution within a cell or tissue for microscopic imaging through the physical expansion of the sample. In this study, we validate the use of U-ExM in Trypanosoma brucei measuring the expansion factors of several different compartments/organelles and thus verify the isotropic expansion of the cell. We furthermore demonstrate the use of this sample preparation protocol for future studies by visualizing the nucleus and kDNA, as well as proteins of the cytoskeleton, the basal body, the mitochondrion and the endoplasmic reticulum. Lastly, we discuss the challenges and opportunities of U-ExM.

Expansion microscopy facilitates quantitative super-resolution studies of cytoskeletal structures in kinetoplastid parasites

Expansion microscopy (ExM) has become a powerful super-resolution method in cell biology. It is a simple, yet robust approach, which does not require any instrumentation or reagents beyond those present in a standard microscopy facility. In this study, we used kinetoplastid parasites Trypanosoma brucei and Leishmania major, which possess a complex, yet well-defined microtubule-based cytoskeleton, to demonstrate that this method recapitulates faithfully morphology of structures as previously revealed by a combination of sophisticated electron microscopy (EM) approaches. Importantly, we also show that due to the rapidness of image acquisition and three-dimensional reconstruction of cellular volumes ExM is capable of complementing EM approaches by providing more quantitative data. This is demonstrated on examples of less well-appreciated microtubule structures, such as the neck microtubule of T. brucei or the pocket, cytosolic and multivesicular tubule-associated microtubules of L. major. We further demonstrate that ExM enables identifying cell types rare in a population, such as cells in mitosis and cytokinesis. Three-dimensional reconstruction of an entire volume of these cells provided details on the morphology of the mitotic spindle and the cleavage furrow. Finally, we show that established antibody markers of major cytoskeletal structures function well in ExM, which together with the ability to visualize proteins tagged with small epitope tags will facilitate studies of the kinetoplastid cytoskeleton.

Structural and functional studies of the first tripartite protein complex at the Trypanosoma brucei flagellar pocket collar

The flagellar pocket (FP) is the only endo- and exocytic organelle in most trypanosomes and, as such, is essential throughout the life cycle of the parasite. The neck of the FP is maintained enclosed around the flagellum via the flagellar pocket collar (FPC). The FPC is a macromolecular cytoskeletal structure and is essential for the formation of the FP and cytokinesis. FPC biogenesis and structure are poorly understood, mainly due to the lack of information on FPC composition. To date, only two FPC proteins, BILBO1 and FPC4, have been characterized. BILBO1 forms a molecular skeleton upon which other FPC proteins can, theoretically, dock onto. We previously identified FPC4 as the first BILBO1 interacting partner and demonstrated that its C-terminal domain interacts with the BILBO1 N-terminal domain (NTD). Here, we report by yeast two-hybrid, bioinformatics, functional and structural studies the characterization of a new FPC component and BILBO1 partner protein, BILBO2 (Tb927.6.3240). Further, we demonstrate that BILBO1 and BILBO2 share a homologous NTD and that both domains interact with FPC4. We have determined a 1.9 Å resolution crystal structure of the BILBO2 NTD in complex with the FPC4 BILBO1-binding domain. Together with mutational analyses, our studies reveal key residues for the function of the BILBO2 NTD and its interaction with FPC4 and evidenced a tripartite interaction between BILBO1, BILBO2, and FPC4. Our work sheds light on the first atomic structure of an FPC protein complex and represents a significant step in deciphering the FPC function in Trypanosoma brucei and other pathogenic kinetoplastids.

Trypanosomes belong to a group of zoonotic, protist, parasites that are found in Africa, Asia, South America, and Europe and are responsible for severe human and animal diseases. They all have a common structure called the flagellar pocket (FP). In most trypanosomes, all macromolecular exchanges between the trypanosome and the environment occur via the FP. The FP is thus essential for cell viability and evading the host immune response. We have been studying the flagellar pocket collar (FPC), an enigmatic macromolecular structure at the neck of the FP, and demonstrated its essentiality for the biogenesis of the FP. We demonstrated that BILBO1 is an essential protein of the FPC that interacts with other proteins including a microtubule-binding protein FPC4.

Here we identify another bona fide FPC protein, BILBO2, so named because of close similarity with BILBO1 in protein localization and functional domains. We demonstrate that BILBO1 and BILBO2 share a common N-terminal domain involved in the interaction with FPC4, and illustrate a tripartite interaction between BILBO1, BILBO2, and FPC4. Our study also provides the first atomic view of two FPC components. These data represent an additional step in deciphering the FPC structure and function in T. brucei.

First person – Simona Amodeo

First Person is a series of interviews with the first authors of a selection of papers published in Journal of Cell Science, helping early-career researchers promote themselves alongside their papers. Simona Amodeo is first author on ‘Characterization of the novel mitochondrial genome segregation factor TAP110 in Trypanosoma brucei’, published in JCS. Simona conducted the research described in this article while a PhD student in the lab of Torsten Ochsenreiter at the Institute of Cell Biology, University of Bern, Switzerland. She is now a postdoctoral researcher in the lab of Professor André Schneider at the Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, investigating mitochondrial biogenesis and ribosomes in Trypanosoma brucei.