Abstract:Background
Ticks represent a major health issue for humans and domesticated animals. Exploring the expression landscape of the tick’s central nervous system (CNS), known as the synganglion, would be an important step in understanding tick physiology and in managing tick-borne diseases, but studies on that topic are still relatively scarce. Neuron-specific genes like the cys-loop ligand-gated ion channels (cys-loop LGICs, or cysLGICs) are important pharmacological targets of acaricides. To date … Show more
“…Assembly of insect genome is challenging due to the large stretch of AT, we cannot exclude defaults in assembly of the human louse genome, as revealed by the missed sequences found in the Phh-GRD genomic annotation and the strikingly very long Phh-GRD gene (> 7 kb) encompassing 3 contigs [20]. Confirmation of the genomic annotation by comparing with the transcriptomics data is a good method to have a complete view of cys-loop LGICs as observed in I. ricinus and I. scapularis [22]. In human body louse, the transcriptomics analysis [34] validated the genomic annotation [23] confirming the absence of Phh-8916.…”
Section: Discussionmentioning
confidence: 96%
“…Interestingly, besides the four well described GABA receptor subunits, an additional gene closely related to GRD and 8916 was described in Blattella germanica (Bg-8916_2) and Periplaneta americana (Pa-8916_2) [16] as well as in the Chelicerata species, Ixodes ricinus (Ir-GABA3), Parasteatoda tepidarorium (Pt-GABA3), and Galendromus occidentalis (Go-GABA3) [22].…”
Human louse (Pediculus humanus) is an obligatory blood feeding ectoparasite with two ecotypes: human body louse (Pediculus humanus humanus), a competent vector of several bacterial pathogens and the human head louse (Pediculus humanus capitis) responsible for pediculosis and affecting millions of people around the globe.
GABA (γ-aminobutyic acid) receptors, members of the cys-loop ligand gated ion channels superfamily, are among the main pharmacological targets for insecticides. In insects, four subunits of GABA receptors: resistant to dieldrin (RDL), glycin like receptor of drosophila (GRD), ligand gated chloride channel homologue3 (LCCH3), and 8916 are well described and form distinct phylogenetic clades revealing orthologous relationships. Our previous studies in human body louse confirmed that subunits Phh-RDL, Phh-GRD and Phh-LCCH3 are well clustered in their corresponding clades. In the present work, we cloned and characterized a putative new GABA receptor subunit in human body louse that we named HoCas for Homologous to Cys-loop alpha like subunit. Extending our analysis to arthropods, HoCas was found to be conserved and clustered in a new (fifth) phylogenetic clade. Interestingly, the gene encoding this subunit is ancestral and has been lost in some insect orders. Compared to the other studied GABA receptor subunits, HoCas exhibited a relatively higher expression level in all development stages and in different tissues of human body louse. These findings improved our understanding of the complex nature of GABA receptors in Pediculus humanus and more generally in arthropods.
“…Assembly of insect genome is challenging due to the large stretch of AT, we cannot exclude defaults in assembly of the human louse genome, as revealed by the missed sequences found in the Phh-GRD genomic annotation and the strikingly very long Phh-GRD gene (> 7 kb) encompassing 3 contigs [20]. Confirmation of the genomic annotation by comparing with the transcriptomics data is a good method to have a complete view of cys-loop LGICs as observed in I. ricinus and I. scapularis [22]. In human body louse, the transcriptomics analysis [34] validated the genomic annotation [23] confirming the absence of Phh-8916.…”
Section: Discussionmentioning
confidence: 96%
“…Interestingly, besides the four well described GABA receptor subunits, an additional gene closely related to GRD and 8916 was described in Blattella germanica (Bg-8916_2) and Periplaneta americana (Pa-8916_2) [16] as well as in the Chelicerata species, Ixodes ricinus (Ir-GABA3), Parasteatoda tepidarorium (Pt-GABA3), and Galendromus occidentalis (Go-GABA3) [22].…”
Human louse (Pediculus humanus) is an obligatory blood feeding ectoparasite with two ecotypes: human body louse (Pediculus humanus humanus), a competent vector of several bacterial pathogens and the human head louse (Pediculus humanus capitis) responsible for pediculosis and affecting millions of people around the globe.
GABA (γ-aminobutyic acid) receptors, members of the cys-loop ligand gated ion channels superfamily, are among the main pharmacological targets for insecticides. In insects, four subunits of GABA receptors: resistant to dieldrin (RDL), glycin like receptor of drosophila (GRD), ligand gated chloride channel homologue3 (LCCH3), and 8916 are well described and form distinct phylogenetic clades revealing orthologous relationships. Our previous studies in human body louse confirmed that subunits Phh-RDL, Phh-GRD and Phh-LCCH3 are well clustered in their corresponding clades. In the present work, we cloned and characterized a putative new GABA receptor subunit in human body louse that we named HoCas for Homologous to Cys-loop alpha like subunit. Extending our analysis to arthropods, HoCas was found to be conserved and clustered in a new (fifth) phylogenetic clade. Interestingly, the gene encoding this subunit is ancestral and has been lost in some insect orders. Compared to the other studied GABA receptor subunits, HoCas exhibited a relatively higher expression level in all development stages and in different tissues of human body louse. These findings improved our understanding of the complex nature of GABA receptors in Pediculus humanus and more generally in arthropods.
“…We also used RNA-Seq data to allow the prediction of expressed and/or specific genes. Two transcriptome libraries of synganglia (Rispe et al 2022) from I. ricinus (PRJEB40724), a library from the whole body of I. ricinus (GFVZ00000000.1), and a pan-transcriptome of 27 different tick species (Charrier et al 2019) were aligned on the four genome assemblies. As for protein sequences, these transcripts were first aligned with BLAT where the best match (based on the alignment score) was selected.…”
Ticks, hematophagous acari, pose a significant threat by transmitting various pathogens to their vertebrate hosts during feeding. Despite advances in tick genomics, high-quality genomes were lacking until recently, particularly in the genusIxodes, which includes the main vectors of Lyme disease. Here, we present the complete genome sequences of four tick species, derived from a single female individual, with a particular focus on the European speciesIxodes ricinus, achieving a chromosome-level assembly. Additionally, draft assemblies were generated for the three otherIxodesspecies,I. persulcatus, I. pacificusandI. hexagonus. The quality of the four genomes and extensive annotation of several important gene families have allowed us to study the evolution of gene repertoires at the level of the genusIxodesand of the tick group. We have determined gene families that have undergone major amplifications during the evolution of ticks, while an expression atlas obtained forI. ricinusreveals striking patterns of specialization both between and within gene families. Notably, several gene family amplifications are associated with a proliferation of single-exon genes. The integration of our data with existing genomes establishes a solid framework for the study of gene evolution, improving our understanding of tick biology. In addition, our work lays the foundations for applied research and innovative control targeting these organisms.
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