Biology subjects

Bordes, A.

Publications and source records attributed to Bordes, A..

3 recordsLinked to original sources

bioRxiv2024

Drivers of host-pathogen community assemblies in European forests and urban green spaces

Major advances in the understanding of infectious diseases have been achieved in the last decades. However, the persistence and re-emergence of pathogens continue to raise public and veterinary health concerns, of which the recent COVID-19 pandemic may be one of the most dramatic examples. Understanding the impact of habitat alterations and concomitant biodiversity loss on pathogen transmission and emergence from wildlife remains challenging. Here, we aim to elucidate the interlinkages between biodiversity and rodent-borne diseases at local and European scales. We present recently collected host-pathogen data from 21 temperate forest sites and eight urban green spaces throughout five European countries, environments where rodents are abundant and human/domestic animals - wildlife interactions are likely to occur. 3766 specimens were analyzed during the period from 2020 to 2022 comprising 15 different small mammal species. Different organ tissues of each specimen were screened for bacteria by either 16S rRNA amplicon sequencing or specific PCR. The presence of antibodies to different families of viruses was screened using immunofluorescent assays. A multitude of pathogens of zoonotic potential from several genera including Bartonella, Borrelia, Mycoplasma, Anaplasma, Neoehrlichia, Leptospira, Orthohantavirus and Orthopoxvirus were detected at non-negligible prevalence in 11 different terrestrial mammal species. A shift in host community composition was observed along the anthropization gradient with more urban adapters in more anthropized sites. Pathogen richness increased with an increase in host species diversity, following the "host-diversity begets parasite-diversity" hypothesis. The absence of some vector-transmitted parasites in urban areas suggests a shift in pathogen community along the anthropization gradient. Host species and host intrinsic factors were dominant explanatory variables for endoparasitic Mycoplasma species and Sarcocystidae, while extrinsic environmental and climatic factors where influential in explaining variations in occurrences of several vector-transmitted pathogens. Apodemus sylvaticus and Clethrionomys glareolus were important connector host species in respectively urban green spaces and temperate forests. Increased host diversity, but not anthropization, correlated with a richer pathogen community. These results ultimately lead to an increased understanding of the complex host-pathogen system at the local landscape that can aid future management decisions and support the public health sector.

ecology↗

bioRxiv2023

Divergence and gene flow history at two large chromosomal inversions involved in long-snouted seahorse ecotype formation

Chromosomal inversions can play an important role in divergence and reproductive isolation by building and maintaining distinct allelic combinations between evolutionary lineages. Alternatively, they can take the form of balanced polymorphisms that segregate within populations over time until one arrangement becomes fixed. Many questions remain about how these different inversion polymorphisms arise, how the mechanisms responsible for their long-term maintenance interact, and ultimately how they contribute to speciation. The long-snouted seahorse (Hippocampus guttulatus) is known to be subdivided into partially isolated lineages and marine-lagoon ecotypes differentiated by structural variation. Here, we aim to characterise these differences along the entire genome, and to reconstruct their history and role in ecotype formation. We generated a near chromosome-level reference genome assembly and described genome-wide patterns of diversity and divergence through the analysis of 112 whole-genome sequences from Atlantic, Mediterranean, and Black Sea populations. Combined with linked-read sequencing data, we found evidence for two megabase-scale chromosomal inversions showing contrasted allele frequency patterns across the species range. We reveal that these inversions represent ancient intraspecific polymorphisms, one being likely maintained by divergent selection, and the other by associative overdominance. Haplotype combinations characterising Mediterranean ecotypes also suggest the existence of potential interactions between the two inversions, possibly driven by environment-dependent fitness effects. Lastly, we detected gene flux eroding divergence between inverted alleles at varying levels between the two inversions, with a likely impact on their long-term dynamics.

genomics↗

bioRxiv2023

Homozygous haplotype deficiency in Manech Tete Rousse dairy sheep revealed a nonsense variant in MMUT gene affecting newborn lamb viability

Recessive deleterious variants are known to segregate in livestock populations as in human, and some may cause lethality when homozygous. By scanning the genome of 6,845 Manech Tete Rousse dairy sheep using phased 50k SNP genotypes and pedigree data, we searched for deficiency in homozygous haplotype (DHH). Five Manech Tete Rousse deficient homozygous haplotypes (MTRDHH1 to 5) were identified with a homozygous deficiency ranging from 84% to 100%. These haplotypes are located on OAR1 (MTRDHH2 and 3), OAR10 (MTRDHH4), OAR13 (MTRDHH5) and OAR20 (MTRDHH1), and have frequencies ranging from 7.8% to 16.6%. When comparing at-risk mating between DHH carriers to safe mating between non-carriers, two DHH (MTRDHH1 and 2) showed significant effects on decreasing artificial insemination success and/or increasing stillbirth rate. We particularly investigated the MTRDHH1 haplotype highly increasing stillbirth rate, and we identified a single nucleotide variant (SNV) inducing a premature stop codon (p.Gln409*) in the MMUT gene (methylmalonyl-CoA mutase) by using a whole genome sequencing (WGS) approach. We generated homozygous lambs for the MMUT mutation by oriented mating, and most of them died within the first 24h after birth without any obvious clinical defect. RT-qPCR and western blotting performed on post-mortem liver and kidney biological samples showed a decreased expression of MMUT mRNA in the liver and absence of a full-length MMUT protein in mutated homozygous lambs. In parallel, MTRDHH4 and MTRDHH5 showed partial association with variants in RXFP2 and ASIP genes, respectively, already known to control horned/polled and coat color phenotypes in sheep, two morphological traits accounting in the MTR breed standard. Further investigations are needed to identified the supposed recessive deleterious variant hosted by MTRDHH2 and MTRDHH3. Anyway, an appropriate management of these haplotypes/variants in the MTR dairy sheep selection program should increase the overall fertility and lamb survival. Author SummaryIn this article, we used reverse genetics screen in ovine using large genotype data available in the framework of genomic selection program in Manech Tete Rousse dairy sheep. We identified five genomic regions with a highly significant deficit in homozygous animal. These regions are thus supposed to host recessive deleterious mutations. In one of these genomic regions, we identified a nonsense mutation in MMUT that alters the functioning of this essential gene of cell metabolism, causing perinatal mortality of homozygous lambs. In this work, we also identified other regions possibly associated with morphological appearance part of the breed standard such as polledness and coat color. Increasing knowledge in these genomic regions will help the future genetic management of the Manech Tete Rousse breed, particularly to reduce lamb mortality.

genomics↗