Comparative Genomic Analysis of six Glossina Genomes, Vectors of African Trypanosomes

Background: Tsetse flies (Glossina sp.) are the vectors of human and animal trypanosomiasis throughout subSaharan Africa. Tsetse flies are distinguished from other Diptera by unique adaptations, including lactation and the birthing of live young (obligate viviparity), a vertebrate blood-specific diet by both sexes, and obligate bacterial symbiosis. This work describes the comparative analysis of six Glossina genomes representing three sub-genera: Morsitans (G. morsitans morsitans, G. pallidipes, G. austeni), Palpalis (G. palpalis, G. fuscipes), and Fusca (G. brevipalpis) which represent different habitats, host preferences, and vectorial capacity. Results: Genomic analyses validate established evolutionary relationships and sub-genera. Syntenic analysis of Glossina relative to Drosophila melanogaster shows reduced structural conservation across the sex-linked X chromosome. Sex-linked scaffolds show increased rates of female-specific gene expression and lower evolutionary rates relative to autosome associated genes. Tsetse-specific genes are enriched in protease, odorant-binding, and helicase activities. Lactation-associated genes are conserved across all Glossina species while male seminal proteins are rapidly evolving. Olfactory and gustatory genes are reduced across the genus relative to other insects. Visionassociated Rhodopsin genes show conservation of motion detection/tracking functions and variance in the Rhodopsin detecting colors in the blue wavelength ranges. Conclusions: Expanded genomic discoveries reveal the genetics underlying Glossina biology and provide a rich body of knowledge for basic science and disease control. They also provide insight into the evolutionary biology underlying novel adaptations and are relevant to applied aspects of vector control such as trap design and discovery of novel pest and disease control strategies

Genome sequence of the tsetse fly (Glossina morsitans):Vector of African trypanosomiasis

Tsetse flies are the sole vectors of human African trypanosomiasis throughout sub-Saharan Africa. Both sexes of adult tsetse feed exclusively on blood and contribute to disease transmission. Notable differences between tsetse and other disease vectors include obligate microbial symbioses, viviparous reproduction, and lactation. Here, we describe the sequence and annotation of the 366-megabase Glossina morsitans morsitans genome. Analysis of the genome and the 12,308 predicted protein-encoding genes led to multiple discoveries, including chromosomal integrations of bacterial (Wolbachia) genome sequences, a family of lactation-specific proteins, reduced complement of host pathogen recognition proteins, and reduced olfaction/chemosensory associated genes. These genome data provide a foundation for research into trypanosomiasis prevention and yield important insights with broad implications for multiple aspects of tsetse biology.IS

Comparative genomic analysis of six Glossina genomes, vectors of African trypanosomes.

BACKGROUND Tsetse flies (Glossina sp.) are the vectors of human and animal trypanosomiasis throughout sub-Saharan Africa. Tsetse flies are distinguished from other Diptera by unique adaptations, including lactation and the birthing of live young (obligate viviparity), a vertebrate blood-specific diet by both sexes, and obligate bacterial symbiosis. This work describes the comparative analysis of six Glossina genomes representing three sub-genera: Morsitans (G. morsitans morsitans, G. pallidipes, G. austeni), Palpalis (G. palpalis, G. fuscipes), and Fusca (G. brevipalpis) which represent different habitats, host preferences, and vectorial capacity. RESULTS Genomic analyses validate established evolutionary relationships and sub-genera. Syntenic analysis of Glossina relative to Drosophila melanogaster shows reduced structural conservation across the sex-linked X chromosome. Sex-linked scaffolds show increased rates of female-specific gene expression and lower evolutionary rates relative to autosome associated genes. Tsetse-specific genes are enriched in protease, odorant-binding, and helicase activities. Lactation-associated genes are conserved across all Glossina species while male seminal proteins are rapidly evolving. Olfactory and gustatory genes are reduced across the genus relative to other insects. Vision-associated Rhodopsin genes show conservation of motion detection/tracking functions and variance in the Rhodopsin detecting colors in the blue wavelength ranges. CONCLUSIONS Expanded genomic discoveries reveal the genetics underlying Glossina biology and provide a rich body of knowledge for basic science and disease control. They also provide insight into the evolutionary biology underlying novel adaptations and are relevant to applied aspects of vector control such as trap design and discovery of novel pest and disease control strategies

Steps in the chemogenomics repositioning workflow and their corresponding results.

<p>The yellow boxes represent <i>P</i>. <i>falciparum</i> sequences, drug targets are shown in blue boxes and drugs in green. Excluded drugs and proteins target have red box outlines.</p

IC₅₀ values of some previously tested approved drugs that were predicted to have antiplasmodial activity.

<p>IC₅₀ values of some previously tested approved drugs that were predicted to have antiplasmodial activity.</p

Comparison of conserved amino acid residues.

<p>(A) ConSurf server MSA results (color coded according to conservation scores) of the drug target, the human tubulin beta-1 (NCBI accession number NP_110400.1) is overlaid above its BLAST pair-wise alignment with its <i>P</i>. <i>falciparum</i> homolog (NCBI accession number XP_001347369.1). The percent of the shared conserved residues was then determined; (B) 3D molecular structure of the human tubulin beta-1 chain with residues color coded according to their conservations scores, this was part of the ConSurf server results.</p

Target-similarity search using <i>Plasmodium falciparum</i> proteome identifies approved drugs with anti-malarial activity and their possible targets

<div><p>Malaria causes about half a million deaths annually, with <i>Plasmodium falciparum</i> being responsible for 90% of all the cases. Recent reports on artemisinin resistance in Southeast Asia warrant urgent discovery of novel drugs for the treatment of malaria. However, most bioactive compounds fail to progress to treatments due to safety concerns. Drug repositioning offers an alternative strategy where drugs that have already been approved as safe for other diseases could be used to treat malaria. This study screened approved drugs for antimalarial activity using an <i>in silico</i> chemogenomics approach prior to <i>in vitro</i> verification. All the <i>P</i>. <i>falciparum</i> proteins sequences available in NCBI RefSeq were mined and used to perform a similarity search against DrugBank, TTD and STITCH databases to identify similar putative drug targets. Druggability indices of the potential <i>P</i>. <i>falciparum</i> drug targets were obtained from TDR targets database. Functional amino acid residues of the drug targets were determined using ConSurf server which was used to fine tune the similarity search. This study predicted 133 approved drugs that could target 34 <i>P</i>. <i>falciparum</i> proteins. A literature search done at PubMed and Google Scholar showed 105 out of the 133 drugs to have been previously tested against malaria, with most showing activity. For further validation, drug susceptibility assays using SYBR Green I method were done on a representative group of 10 predicted drugs, eight of which did show activity against <i>P</i>. <i>falciparum</i> 3D7 clone. Seven had IC₅₀ values ranging from 1 μM to 50 μM. This study also suggests drug-target association and hence possible mechanisms of action of drugs that did show antiplasmodial activity. The study results validate the use of proteome-wide target similarity approach in identifying approved drugs with activity against <i>P</i>. <i>falciparum</i> and could be adapted for other pathogens.</p></div

Druggability indices of predicted <i>P</i>. <i>falciparum</i> drug targets.

<p>Druggability indices of predicted <i>P</i>. <i>falciparum</i> drug targets.</p

Details of approved drugs predicted to target <i>P</i>. <i>falciparum</i> proteins that have not been tested.

<p>Details of approved drugs predicted to target <i>P</i>. <i>falciparum</i> proteins that have not been tested.</p

<i>In vitro</i> activities of drugs tested against <i>P</i>. <i>falciparum</i> 3D7 strain.

<p><i>In vitro</i> activities of drugs tested against <i>P</i>. <i>falciparum</i> 3D7 strain.</p