Towards a framework for the evolutionary genomics of Kinetoplastids: what kind of data and how much?

The current status of kinetoplastids phylogeny and evolution is discussed in view of the recent progresses on genomics. Some ideas on a potential framework for the evolutionary genomics of kinetoplastids are presented

Identifikace a charakterizace genetických aberací dětských akutních leukémií

Childhood acute leukemias are genetically complex disorders, with recurrent or random aberrations found in most patients. Their proper functional characterization is crucial for understanding the role they play in the process of leukemogenesis. We aimed to identify and characterize the genetic background of two leukemic entities. The transient myeloproliferative disorder (TMD) is a preleukemic condition that occurs in 10% of newborns with Down syndrome. Trisomy 21 together with in-utero gained mutations in the GATA1 gene are essential in TMD and represent an ideal "multi-hit" model to study leukemogenesis. We investigated an alternative pathogenic mechanism enabling TMD development in a confirmed absence of trisomy 21. Novel deletions in the GATA1 and JAK1 genes were described as potential drivers of this TMD. The deletion D65_C228 in GATA1 results in the expression of an aberrant isoform, which is predicted to lose transactivation potential and, more importantly, to partially lose the ability of recognizing physiological DNA binding sites, possibly triggering TMD alone. Our thorough characterization of JAK1 F636del questions its role in TMD development. Analysis of JAK/STAT signaling suggested decrease of kinase activity upon F636 loss. Cells harboring the aberrant JAK1 did not obtain cytokine-...Dětské akutní leukémie jsou geneticky komplexní poruchy hematopoézy. U většiny pacientů se vyskytují rekurentní či náhodné aberace, jejichž pečlivá funkční charakterizace je zásadní pro pochopení role, kterou hrají v procesu leukemogeneze. Naším cílem byla identifikace a charakterizace genetického pozadí dvou leukemických entit. Transientní myeloproliferativní porucha (TMD) je preleukémie, která postihuje 10% novorozenců s Downovým syndromem. Trisomie 21 chromozomu a in-utero získané mutace v genu GATA1 jsou kauzální pro vznik TMD a společně představují ideální "více-zásahový" model leukemogeneze. Zaměřili jsme se na zkoumání alternativního mechanismu vzniku TMD bez účasti trisomie 21. U jedinečného případu TMD jsme jako potenciálně spouštěcí aberace popsali nové delece v genech GATA1 a JAK1. Delece D65_C228 v GATA1 způsobuje tvorbu poškozené izoformy, u níž se předpokládá ztráta transaktivační schopnosti a rovněž částečná ztráta vazby ke specifickým vazebným místům v DNA, což může stačit ke spuštění TMD. Námi provedená podrobná charakterizace delece F636 v JAK1 zpochybňuje význam této aberace pro patogenezi TMD. Analýza signalizace JAK/STAT odhalila pokles kinázové aktivity po ztrátě F636. Růst buněk Ba/F3, které vytvářejí poškozený JAK1, je závislý na cytokinech, podobně jako je tomu u buněk...Department of Paediatric Haematology and OncologyKlinika dětské hematologie a onkologie2. lékařská fakultaSecond Faculty of Medicin

Roles of the Nfu Fe-S targeting factors in the trypanosome mitochondrion

Iron–sulphur clusters (ISCs) are protein co-factors essential for a wide range of cellular functions. The core iron–sulphur cluster assembly machinery resides in the mitochondrion, yet due to export of an essential precursor from the organelle, it is also needed for cytosolic and nuclear iron–sulphur cluster assembly. In mitochondria all [4Fe–4S] iron–sulphur clusters are synthesised and transferred to specific apoproteins by so-called iron–sulphur cluster targeting factors. One of these factors is the universally present mitochondrial Nfu1, which in humans is required for the proper assembly of a subset of mitochondrial [4Fe–4S] proteins. Although most eukaryotes harbour a single Nfu1, the genomes of Trypanosoma brucei and related flagellates encode three Nfu genes. All three Nfu proteins localise to the mitochondrion in the procyclic form of T. brucei, and TbNfu2 and TbNfu3 are both individually essential for growth in bloodstream and procyclic forms, suggesting highly specific functions for each of these proteins in the trypanosome cell. Moreover, these two proteins are functional in the iron–sulphur cluster assembly in a heterologous system and rescue the growth defect of a yeast deletion mutant

Causes and effects of loss of classical non-homologous end joining pathway in parasitic eukaryotes

We report frequent losses of components of the classical nonhomologous end joining pathway (C-NHEJ), one of the main eukaryotic tools for end joining repair of DNA double-strand breaks, in several lineages of parasitic protists. Moreover, we have identified a single lineage among trypanosomatid flagellates that has lost Ku70 and Ku80, the core C-NHEJ components, and accumulated numerous insertions in many protein-coding genes. We propose a correlation between these two phenomena and discuss the possible impact of the C-NHEJ loss on genome evolution and transition to the parasitic lifestyle

The convoluted history of haem biosynthesis

ABSTRACT: The capacity of haem to transfer electrons, bind diatomic gases, and catalyse various biochemical reactions makes it one of the essential biomolecules on Earth and one that was likely used by the earliest forms of cellular life. Since the description of haem biosynthesis, our understanding of this multi‐step pathway has been almost exclusively derived from a handful of model organisms from narrow taxonomic contexts. Recent advances in genome sequencing and functional studies of diverse and previously neglected groups have led to discoveries of alternative routes of haem biosynthesis that deviate from the ‘classical’ pathway. In this review, we take an evolutionarily broad approach to illuminate the remarkable diversity and adaptability of haem synthesis, from prokaryotes to eukaryotes, showing the range of strategies that organisms employ to obtain and utilise haem. In particular, the complex evolutionary histories of eukaryotes that involve multiple endosymbioses and horizontal gene transfers are reflected in the mosaic origin of numerous metabolic pathways with haem biosynthesis being a striking case. We show how different evolutionary trajectories and distinct life strategies resulted in pronounced tensions and differences in the spatial organisation of the haem biosynthesis pathway, in some cases leading to a complete loss of a haem‐synthesis capacity and, rarely, even loss of a requirement for haem altogether

Genome of Ca. Pandoraea novymonadis, an Endosymbiotic Bacterium of the Trypanosomatid Novymonas esmeraldas

We have sequenced, annotated, and analyzed the genome of Ca. Pandoraea novymonadis, a recently described bacterial endosymbiont of the trypanosomatid Novymonas esmeraldas. When compared with genomes of its free-living relatives, it has all the hallmarks of the endosymbionts’ genomes, such as significantly reduced size, extensive gene loss, low GC content, numerous gene rearrangements, and low codon usage bias. In addition, Ca. P. novymonadis lacks mobile elements, has a strikingly low number of pseudogenes, and almost all genes are single copied. This suggests that it already passed the intensive period of host adaptation, which still can be observed in the genome of Polynucleobacter necessarius, a certainly recent endosymbiont. Phylogenetically, Ca. P. novymonadis is more related to P. necessarius, an intracytoplasmic bacterium of free-living ciliates, than to Ca. Kinetoplastibacterium spp., the only other known endosymbionts of trypanosomatid flagellates. As judged by the extent of the overall genome reduction and the loss of particular metabolic abilities correlating with the increasing dependence of the symbiont on its host, Ca. P. novymonadis occupies an intermediate position P. necessarius and Ca. Kinetoplastibacterium spp. We conclude that the relationships between Ca. P. novymonadis and N. esmeraldas are well-established, although not as fine-tuned as in the case of Strigomonadinae and their endosymbionts

Novel organization of mitochondrial minicircles and guide RNAs in the zoonotic pathogen Trypanosoma lewisi

Abstract Kinetoplastid flagellates are known for several unusual features, one of which is their complex mitochondrial genome, known as kinetoplast (k) DNA, composed of mutually catenated maxi- and minicircles. Trypanosoma lewisi is a member of the Stercorarian group of trypanosomes which is, based on human infections and experimental data, now considered a zoonotic pathogen. By assembling a total of 58 minicircle classes, which fall into two distinct categories, we describe a novel type of kDNA organization in T. lewisi. RNA-seq approaches allowed us to map the details of uridine insertion and deletion editing events upon the kDNA transcriptome. Moreover, sequencing of small RNA molecules enabled the identification of 169 unique guide (g) RNA genes, with two differently organized minicircle categories both encoding essential gRNAs. The unprecedented organization of minicircles and gRNAs in T. lewisi broadens our knowledge of the structure and expression of the mitochondrial genomes of these human and animal pathogens. Finally, a scenario describing the evolution of minicircles is presented

Towards disentangling the classification of freshwater fish trypanosomes

Currently, new species of freshwater fish trypanosomes, which are economically important parasites, are being described based on subjectively selected features, i.e., their cell morphology and the host species. We have performed detailed phylogenetic and haplotype diversity analyses of all 18S rRNA genes available for freshwater fish trypanosomes, including the newly obtained sequences of Trypanosoma carassii and Trypanosoma danilewskyi. Based on a sequence similarity of 99.5%, we divide these trypanosomes into 15 operational taxonomic units, and propose three nominal scenarios for distinguishing T. carassii and other aquatic trypanosomes. We find evidences for the existence of a low number of freshwater fish trypanosomes, with T. carassii having the widest geographic and host ranges. Our analyses support the existence of an umbrella complex composed of T. carassii and two sister species