Identification of ASYNAPTIC4, a Component of the Meiotic Chromosome Axis

International audienceDuring the leptotene stage of prophase I of meiosis, chromatids become organized into a linear looped array via a protein axis that forms along the loop bases. Establishment of the axis is essential for the subsequent synapsis of the homologous chromosome pairs and the progression of recombination to form genetic crossovers. Here, we describe ASYNAPTIC4 (ASY4), a meiotic axis protein in Arabidopsis (Arabidopsis thaliana). ASY4 is a small coiled-coil protein that exhibits limited sequence similarity with the carboxyl-terminal region of the axis protein ASY3. We used enhanced yellow fluorescent protein-tagged ASY4 to show that ASY4 localizes to the chromosome axis throughout prophase I. Bimolecular fluorescence complementation revealed that ASY4 interacts with ASY1 and ASY3, and yeast two-hybrid analysis confirmed a direct interaction between ASY4 and ASY3. Mutants lacking full-length ASY4 exhibited defective axis formation and were unable to complete synapsis. Although the initiation of recombination appeared to be unaffected in the asy4 mutant, the number of crossovers was reduced significantly, and crossovers tended to group in the distal parts of the chromosomes. We conclude that ASY4 is required for normal axis and crossover formation. Furthermore, our data suggest that ASY3/ASY4 are the functional homologs of the mammalian SYCP2/SYCP3 axial components

ÉTUDE DE NBL1, UNE PROTÉINE DE TRICHINELLA SPIRALIS PRESENTANT UN INTÉRÊT POUR LE DÉVELOPPEMENT DE NOUVEAUX OUTILS DE LUTTE CONTRE CE PARASITE ZOONOTIQUE

La trichinellose est une zoonose provoquée par la consommation de viande crue ou insuffisamment cuite d’animaux infestés par des larves du nématode Trichinella spp. Cette parasitose est une maladie réglementée régulièrement émergente ou ré-émergente dans différentes parties du monde. Trichinella spp. est ainsi un parasite qui nécessite une pression de contrôle permanente puisqu’il est impossible de l’éradiquer compte tenu de la grande diversité d’hôtes et de sa circulation dans la faune sauvage à l’échelle mondiale. La viande porcine est la principale source de contamination de l’Homme. Les outils sérologiques disponibles ne permettent pas de détecter le parasite suffisamment tôt chez le porc, d’autant plus si la charge parasitaire est faible. Le développement de nouvelles cibles pour le dépistage est donc un enjeu majeur dans la surveillance des élevages de porcs hors-sol mais aussi dans la perspective à long terme de remplacer le test réglementaire actuel (digestion artificielle de muscles).La protéine NBL1 a été identifiée précédemment au laboratoire chez les larves nouveau-nées (L1NN) de Trichinella spiralis et représente une cible intéressante. Cette protéase à sérine a été sélectionnée par immunocriblage d’une banque soustractive du stade L1NN et a montré un potentiel antigénique intéressant pour le développement d’outils de détection précoce des infestations à Trichinella ou pour le développement de vaccins contre ce parasite.Les études génomique et protéogénomique de cette protéine chez T. spiralis, T. nativa, T. britovi, et T. pseudospiralis ont mis en évidence une forte homologie entre ces espèces et tout particulièrement au niveau de la partie C-terminale qui a été identifiée comme fortement antigénique chez T. spiralis. L’analyse transcriptomique des stades L1M, Adultes 5 jours et L1NN confirme bien le fait que cette protéine est principalement présente au stade L1NN. Des tentatives d’inhibition transitoire par siRNA ciblant cette protéine au stade L1NN ont été initiées dans le cadre de ce travail mais n’ont pas permis d’identifier sa fonction in vivo. Cette étude apporte de nouvelles connaissances sur la séquence conservée de la protéine NBL1 chez les différentes espèces de Trichinella et la transcription des ARN par le stade L1NN majoritairement

Ring trial on comparison of articial digestion methods for detection of encapsulated Trichinella spiralis larvae in porkmeat

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Ring trial on comparison of articial digestion methods for detection of encapsulated Trichinella spiralis larvae in porkmeat

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Functional characterization of three G protein-coupled acetylcholine receptors in parasitic nematode Trichinella spiralis

The physiological significance of metabotropic acetylcholine receptors in parasitic nematodes remains largely unexplored. Here, three different Trichinella spiralis G protein-coupled acetylcholine receptors (TsGAR-1, -2, and -3) were identified in the genome of T. spiralis. The phylogenetic analyses showed that TsGAR-1 and -2 receptors belong to a distinct clade specific to invertebrates, while TsGAR-3 is closest to the cluster of mammalian-type muscarinic acetylcholine receptors (mAChR). The mRNA of TsGAR-1, -2, and -3 was detected in muscle larvae, newborn larvae, and adults. The functional aequorin-based assay in Chinese hamster ovary cells revealed that all three types of T. spiralis GARs trigger the Gq/11 pathway upon activation of the receptor with the acetylcholine ligand. TsGAR-1 and TsGAR-2 showed atypical affinity with classical muscarinic agonists, while TsGAR-3 was sensitive to all muscarinic agonists tested. High concentrations of propiverine antagonist blocked the activities of all three TsGARs, while atropine and scopolamine antagonists effectively inhibited only TsGAR-3. Our data indicate that the distinct pharmacological profile of TsGAR-1 and -2 receptors, as well as the phylogenetic distance between them and their mammalian orthologs, place them as attractive targets for the development of selective anthelmintic drugs interfering with nematodes’ cholinergic system

Molecular identification of Trichinella species by multiplex PCR: new insight for Trichinella murrelli

In order to identify Trichinella at the species level, the commonly used test is a multiplex PCR, allowing the discrimination of nine out of the twelve taxa described so far. This test is based on five primer pairs amplifying fragments of the large subunit rDNA. Each taxon produces one or two bands of different sizes, resulting in a specific band pattern. By multiplex PCR, Trichinella murrelli shows two bands of 127 bp and 316 bp. However, a third band of 256 bp can occur. This band can lead to misidentification, since it is similar to the 253 bp band displayed by Trichinella britovi. BLAST analysis confirmed that the 256 bp band is from T. murrelli. The aim of this short note is to inform analysts that T. murrelli larvae may display either two- or three-band patterns

Molecular identification of Trichinella species by multiplex PCR: new insight for Trichinella murrelli

In order to identify Trichinella at the species level, the commonly used test is a multiplex PCR, allowing the discrimination of nine out of the twelve taxa described so far. This test is based on five primer pairs amplifying fragments of the large subunit rDNA. Each taxon produces one or two bands of different sizes, resulting in a specific band pattern. By multiplex PCR, Trichinella murrelli shows two bands of 127 bp and 316 bp. However, a third band of 256 bp can occur. This band can lead to misidentification, since it is similar to the 253 bp band displayed by Trichinella britovi. BLAST analysis confirmed that the 256 bp band is from T. murrelli. The aim of this short note is to inform analysts that T. murrelli larvae may display either two-or three-band patterns.Afin d’identifier les Trichinella au niveau de l’espèce, le test couramment utilisé est une PCR multiplex, permettant la discrimination de neuf des douze taxons décrits jusqu’à présent. Ce test est basé sur cinq paires d’amorces amplifiant des fragments de la grande sous-unité l’ADN ribosomal. Chaque taxon produit une ou deux bandes de tailles différentes, résultant en un patron de bandes spécifique. Par PCR multiplex, Trichinella murrelli présente deux bandes de 127 pb et 316 pb. Cependant, une troisième bande de 256 pb peut s’observer. Cette bande peut être la cause d’une erreur d’identification, car elle est similaire à la bande de 253 pb affichée par Trichinella britovi. L’analyse BLAST a confirmé que la bande à 256 pb provient de T. murrelli. Le but de cette note est d’informer les analystes que les larves de T. murrelli peuvent présenter des patrons à deux ou trois bandes

Exploring the Susceptibility of C3H Mice to Tick-Borne Encephalitis Virus Infection: Implications for Co-Infection Models and Understanding of the Disease

Ticks and tick-borne diseases (TBDs) are increasingly recognized as a critical One Health concern. Tick-borne encephalitis (TBE), a severe neuro infection caused by the tick-borne encephalitis virus (TBEV), has emerged as a significant global public health threat. Laboratory animals, particularly mice, have played a pivotal role in advancing our understanding of TBD pathogenesis. Notably, BALB/c mice have been employed as models due to their heightened susceptibility to TBEV. However, the use of C3H mice, valued for other tick-borne pathogens, has remained unexplored for TBEV until now. This study aimed to assess the susceptibility of C3H mice to TBEV infection, laying the groundwork for future co-infection models involving TBEV and Borrelia. Experiments revealed that C3H mice are susceptible to TBEV infection through subcutaneous inoculation. While 102 PFU/mouse appeared necessary for full infection, 103 PFU/mouse induced consistent symptoms. However, subsequent assessment of ticks’ acquisition of TBEV from infected mice met with limited success, raising questions about optimal infectious doses for natural infection. These findings suggest the potential of C3H mice for studying TBEV and co-infections with other pathogens, particularly Borrelia. Further exploration of the interplay between these pathogens, their transmission dynamics, and disease severity could enhance prevention and control strategies

Emergence of the trematode Alaria alata in wild boar in France

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Emergence of the trematode Alaria alata in wild boar in France

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