Biology subjects

Cadar, D.

Publications and source records attributed to Cadar, D..

4 recordsLinked to original sources

bioRxiv2025

Morphological and genetic heterogeneity in Aedes aegypti (Diptera: Culicidae) populations across diverse landscapes in West Africa

Native to sub-Saharan Africa, Aedes aegypti has spread across the globe and is now one of the most significant vectors of arboviruses worldwide. However, data on the ranges of its populations remain sparse, and the genetic variability and ecological adaptability in West Africa are still poorly understood. In this study, we characterized the morphological and genetic diversity of Ae. aegypti across four landscape types (urban, peri-urban, rural, and sylvatic sites) in three West African countries (Burkina Faso, Cote dIvoire, and Ghana). Ae. aegypti exhibited significant variation in abdominal scaling patterns across countries and landscape types, with the sylvatic and urban populations in Burkina Faso displaying the highest proportions of white scales (>50% white scales), while black scales predominated among those from Cote dIvoire and Ghana (>80% black scales). Wing shape displayed limited differentiation between the countries, landscape types, and genetic clusters. Bayesian analysis indicated high gene flow among populations, with notable outliers observed in sylvatic sites from Burkina Faso and admixture patterns suggesting possible human-mediated dispersal. Additionally, two major mitochondrial lineages, clades A and B, were identified. Most samples were categorized under clade B, showing no evidence of clustering by country or landscape type. In contrast, clade A comprised primarily sylvatic specimens from Burkina Faso and a single urban individual from Cote dIvoire. These findings highlight the complex interplay of genetic, environmental, and ecological factors shaping the variations in Ae. aegypti populations in West Africa. They provide insights into the phenotypic and genetic diversity of Ae. aegypti, offering valuable implications for understanding arbovirus transmission dynamics and formulating targeted interventions against arboviral diseases.

ecology↗

bioRxiv2025

Ambecovirus, a novel Betacoronavirus subgenus circulating in neotropical bats sheds new light on bat-borne coronaviruses evolution

Understanding the viral diversity harboured by wildlife is essential for effective prediction and prevention of future zoonotic outbreaks. Bats, in particular, are recognized as natural reservoirs for several zoonotic viral pathogens of high impact on public health, including coronaviruses responsible for SARS, the rabies virus, Marburg, Ebola, Nipah and Hendra viruses. However, the large extent of bat viruses remains unexplored, especially in highly biodiverse regions of the Neotropics such as Brazil. We used a meta-transcriptomic to characterize new virus genomes found in blood, oral and anal samples collected from cave- and non-cave bats from Northeast Brazil. From a total of 19 coronavirus-positive bats, we have assembled two complete genomes of a new Betacoronavirus subgenus, named Ambecovirus (American betacoronavirus). The subgenus herein described is phylogenetically placed between the Sarbeco-/Hibeco-/Nebecovirus and the Merbeco-/Embecovirus clades, being basal to the former. While the conserved S2 region of the spike protein retained hallmark domains, including HR1 and HR2, the S1/S2 cleavage site and the furin cleavage site, the S1 region consistently displayed only the N-terminal domain. The receptor-binding domain could not be identified due to high dissimilarity relative to known congeneres. The detection of Ambercovirus in sympatric Pteronotus gymnonotus and Carollia perspicillata bats suggests interspecies transmission. Longitudinal sampling confirmed persistent Ambecovirus infection in P. gymnonotus over multiple years and virus dispersion at a minimum distance of 270 km between caves. The present study confirms that viral diversity in neotropical hosts remains largely unknown not just in Brazil but, likely, in the other countries of the region, supporting the need for a systematic approach to virome exploration and analysis followed by in vitro experimentation to assess zoonotic potential.

evolutionary biology↗

bioRxiv2024

A polytypic species revisited: Phylogenetic and morphological variation, taxonomic status, and geographical distribution of Trachops (Chiroptera: Phyllostomidae)

The taxonomic status of the neotropical bat genus Trachops has been reevaluated through an integrated study that incorporates morphological, morphometric, and molecular data across its extensive geographic range. Our research, which included previously unexamined regions, revealed substantial insights into the diversity within Trachops. The results support the elevation of T. cirrhosus ehrhardti to species status, due to genetic and morphological differences in southeastern Brazil specimens. Conversely, our comprehensive analysis found insufficient evidence to maintain the subspecific distinction of T. c. coffini, which lacks diagnosable morphological characters and is not genetically distinct from T. c. cirrhosus across its distribution range. Additionally, our findings challenge the previous belief of a latitudinal differentiation in body size for Trachops cirrhosus, as specimens from western South America and northeastern South America exhibit similar sizes to those from Central America. These results underscore the importance of revising the taxonomic framework for this bat genus, contributing to a more precise understanding of its evolutionary relationships, and further enhancing conservation efforts, considering the potential threats to the newly recognized T. ehrhardti in the imperiled Atlantic Forest of Brazil.

zoology↗

bioRxiv2023

Proteins differentially expressed between pathogenic and non-pathogenic Entamoeba histolytica clones influence pathogenicity by different mechanisms

Recently, two genes involved in pathogenicity in a mouse model of amoebic liver abscess were identified based on their differential expression between non-pathogenic (A1np) and pathogenic (B2p) clones of the Entamoeba histolytica isolate HM:1-IMSS. While overexpression of a gene encoding the metallopeptidase EhMP8-2 decreases the virulence of the pathogenic clone B2p, overexpression of the gene ehi_127670 (ehhp127), encoding a hypothetical protein, increases the virulence of the non-pathogenic clone A1np, while silencing this gene in B2p decreases virulence. To understand the role of both molecules in determining the pathogenicity of E. histolytica, silencing and overexpression transfectants were characterized in detail. Silencing of ehmp8-2, of the homologous gene ehmp8-1, or of both together in A1np trophozoites significantly altered the transcript levels of 60-350 genes. This strong change in the expression profile caused by the silencing of ehmp8-1 and/or ehmp8-2 implies that these peptidases regulate expression of numerous genes. Consequently, numerous phenotypic characteristics including cytopathic, hemolytic and cysteine peptidase activity were changed in response to their silencing. Silencing of ehhp127 in B2p trophozoites did not affect other genes, whereas overexpression in A1np trophozoites results in an altered expression of approximately 140 genes. EhHP127 appears to be important for trophozoite movement, as silencing negatively affects and overexpression positively affects trophozoite motility. Interestingly, the specific silencing of ehhp127 also impairs cytopathic activity, cysteine peptidase and hemolytic activity. All three molecules of interest, namely EhMP8-1, EhMP8-2, and EhHP127 can be detected in amoeba vesicles. Our results clearly show that the proteins studied here influence the pathogenicity of amoebae in different ways and use entirely different mechanisms to do so. Author summaryThe human pathogen Entamoeba histolytica can live asymptomatically in the intestine or become invasive and cause fatal liver abscesses. Approximately 15,000 people die each year as a result of an amoebic infection. Recently, two clones with different pathogenicity (A1np: non-pathogenic; B2p: pathogenic) derived from the E. histolytica isolate HM:1-IMSS were compared at the transcriptome level. Two highly differentially expressed genes (ehhp127 encoding a hypothetical protein and ehmp8-2 encoding a metallopeptidase) were identified. Analysis of E. histolytica transfectants showed that silencing of ehhp127 and overexpression of ehmp8-2 in B2p trophozoites reduced amoebic liver abscess formation in the mouse model. In this study, we characterized E. histolytica silencing and overexpression transfectants of ehmp8-2, as well as of the homologous gene ehmp8-1 and of ehhp127. It was shown that the altered expression of the metallopeptidase genes has a strong influence on the expression of a large number of genes and that the phenotype is strongly altered as a result. Silencing of ehhp127 does not affect the overall expression profile. However, specific silencing has a negative effect on motility, cysteine peptidase, hemolytic and cytopathic activity. All three molecules were shown to be localized in trophozoite vesicles.

cell biology↗