Novel Insights into the Bovine Polled Phenotype and Horn Ontogenesis in Bovidae

Despite massive research efforts, the molecular etiology of bovine polledness and the developmental pathways involved in horn ontogenesis are still poorly understood. In a recent article, we provided evidence for the existence of at least two different alleles at the Polled locus and identified candidate mutations for each of them. None of these mutations was located in known coding or regulatory regions, thus adding to the complexity of understanding the molecular basis of polledness. We confirm previous results here and exhaustively identify the causative mutation for the Celtic allele (PC) and four candidate mutations for the Friesian allele (PF). We describe a previously unreported eyelash-and-eyelid phenotype associated with regular polledness, and present unique histological and gene expression data on bovine horn bud differentiation in fetuses affected by three different horn defect syndromes, as well as in wild-type controls. We propose the ectopic expression of a lincRNA in PC/p horn buds as a probable cause of horn bud agenesis. In addition, we provide evidence for an involvement of OLIG2, FOXL2 and RXFP2 in horn bud differentiation, and draw a first link between bovine, ovine and caprine Polled loci. Our results represent a first and important step in understanding the genetic pathways and key process involved in horn bud differentiation in Bovidae

A newly described bovine type 2 scurs syndrome segregates with a frame-shift mutation in TWIST1.

The developmental pathways involved in horn development are complex and still poorly understood. Here we report the description of a new dominant inherited syndrome in the bovine Charolais breed that we have named type 2 scurs. Clinical examination revealed that, despite a strong phenotypic variability, all affected individuals show both horn abnormalities similar to classical scurs phenotype and skull interfrontal suture synostosis. Based on a genome-wide linkage analysis using Illumina BovineSNP50 BeadChip genotyping data from 57 half-sib and full-sib progeny, this locus was mapped to a 1.7 Mb interval on bovine chromosome 4. Within this region, the TWIST1 gene encoding a transcription factor was considered as a strong candidate gene since its haploinsufficiency is responsible for the human Saethre-Chotzen syndrome, characterized by skull coronal suture synostosis. Sequencing of the TWIST1 gene identified a c.148_157dup (p.A56RfsX87) frame-shift mutation predicted to completely inactivate this gene. Genotyping 17 scurred and 20 horned founders of our pedigree as well as 48 unrelated horned controls revealed a perfect association between this mutation and the type 2 scurs phenotype. Subsequent genotyping of 32 individuals born from heterozygous parents showed that homozygous mutated progeny are completely absent, which is consistent with the embryonic lethality reported in Drosophila and mouse suffering from TWIST1 complete insufficiency. Finally, data from previous studies on model species and a fine description of type 2 scurs symptoms allowed us to propose different mechanisms to explain the features of this syndrome. In conclusion, this first report on the identification of a potential causal mutation affecting horn development in cattle offers a unique opportunity to better understand horn ontogenesis

Recent genomic contributions to understanding Mycobacterium avium subsp. paratuberculosis evolution and transmission dynamics

International audienceIntroduction and objectives.Paratuberculosis or Johne's disease is a chronic intestinal disease caused by Mycobacterium avium ssp. paratuberculosis (Map), primarily affecting ruminants and present worldwide. Despite the implementation of control programs in most developed countries, and the consequent financial efforts required, the prevalence rate of paratuberculosis remains very high, at around 50% in European herds and 8% in U.S herds. This worrying situation is due to a lack of knowledge about the biology of this pathogen and its transmission dynamics. Map's genomic studies, initiated in 2016, have recently multiplied thanks to the development of 3rd generation sequencing.Here we present a review of the contribution of Map genomic studies to our understanding of this pathogen and the epidemiology of Johne's disease.Materials and methodsThe articles collected for this synthesis encompass more than 820 genomes available in the NCBI SRA, GenBank, and ENA databases and 15 complete genomes. Map strains were distributed over 5 continents and have been isolated from a variety of hosts but mainly ruminants. We selected studies for which epidemiological data were available.Results, discussion and conclusionAnalysis of the pangenome shows that Map is a clonal species with a core genome of 98%. The advent of next-generation sequencing has not only made it possible to establish relationships down to the strain level, but has also revealed genome-wide differences between strains, making it possible to establish Map's population structure by country and between countries. Phylogenetic analyses combined with data on animals, including their movements, provide a better understanding of Map's transmission dynamics. Map genomics has also revealed the notion of mixed infection in animals.Taken together, these data further our knowledge of this pathogen and offer new prospects for improving the prevention and control of Johne's disease

How to predict that some animals respond better to vaccination than others: application to vaccination against Mycoplasma hyopneumoniae in pigs?

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Impact of genetics on microbiota composition and on Salmonella carriage in chicken

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Discovery of Predictors of Mycoplasma hyopneumoniae Vaccine Response Efficiency in Pigs: 16S rRNA Gene Fecal Microbiota Analysis

International audienceThe gut microbiota comprises a large and diverse community of bacteria that play a significant role in swine health. Indeed, there is a tight association between the enteric immune system and the overall composition and richness of the microbiota, which is key in the induction, training and function of the host immunity, and may therefore, influence the immune response to vaccination. Using vaccination againstMycoplasma hyopneumoniae(M. hyo) as a model, we investigated the potential of early-life gut microbiota in predicting vaccine response and explored the post-vaccination dynamics of fecal microbiota at later time points. At 28 days of age (0 days post-vaccination; dpv), healthy piglets were vaccinated, and a booster vaccine was administered at 21 dpv. Blood samples were collected at 0, 21, 28, 35, and 118 dpv to measureM. hyo-specific IgG levels. Fecal samples for 16S rRNA gene amplicon sequencing were collected at 0, 21, 35, and 118 dpv. The results showed variability in antibody response among individual pigs, whilst pre-vaccination operational taxonomic units (OTUs) primarily belonging toPrevotella, [Prevotella],Anaerovibrio, andSutterellaappeared to best-predict vaccine response. Microbiota composition did not differ between the vaccinated and non-vaccinated pigs at post-vaccination time points, but the time effect was significant irrespective of the animals' vaccination status. Our study provides insight into the role of pre-vaccination gut microbiota composition in vaccine response and emphasizes the importance of studies on full metagenomes and microbial metabolites aimed at deciphering the role of specific bacteria and bacterial genes in the modulation of vaccine response