Biology subjects

Henriet, S.

Publications and source records attributed to Henriet, S..

6 recordsLinked to original sources

bioRxiv2026

Single cell sequencing during the entire life cycle reveals cell type diversity in Oikopleura dioica, and pools of genes expressed in the house-producing epithelium

In tunicates, larvaceans represent a fascinating case of evolution, where the chordate body plan has been maintained despite a rapidly evolving genome characterized by strong In contrast to other tunicates, larvaceans keep the chordate body plan during their entire life. They have acquired a highly specialized epithelium in charge of producing the "house", a complex extracellular apparatus used for filter feeding in the plankton. To what extent the house and this epithelium represent true molecular innovations withing chordates is a question for which thorough transcriptomics can bring novel insights. We conducted a developmental profiling of gene expression at the single-cell level in the larvacean Oikopleura dioica. We provide detailed descriptions of cellular transcriptomes associated with the house-synthesizing organ, which permits to define the molecular specifics of epithelial cell territories. We followed their emergence during development, and we identified genes that represent key candidate molecules for regulating the morphogenesis of the house-producing organ. Dynamic changes in gene expression and cell identities during major developmental transitions of the lifecycle illustrate that our dataset effectively allows access to the diversity of O. dioicas cell types in embryos and in adults. The resources presented here constitute critical assets to investigate larvacean biology and evolution for mechanistic and comparative goals.

evolutionary biology↗

bioRxiv2025

Deployment of non-canonical splicing in tunicate genomes is mediated by divergent U2AF function and re-patterning of snRNA m6A modification

In eukaryotes, the critical function of the spliceosome is to remove introns from newly transcribed pre-messenger RNA to produce functional mRNA. Spliced segments normally begin with a GT and end with an AG, and precise intron removal relies on the recognition of terminal dinucleotides by the spliceosomal RNA (snRNA) and by the U2AF heterodimer. Here, we reveal how the modification of these molecules was instrumental for shifting spliceosome specificity, enforcing splicing accuracy in genomes where 95% of introns escape the GT/AG rule. We show that the emergence of non-canonical introns in the Fritillaria borealis lineage is associated with the duplication of each U2AF subunit. Subunit paralogues can be combined to form multiple U2AF complexes that involve novel protein-protein interaction rules. Binding assays on RNA and transcriptome analysis of human cells expressing U2AF subunits show that divergent paralogues can contribute to the recognition of non-canonical splice signals at the 3 end of introns. In transfected cells, levels of N6-methyladenosine (m6A) modification on snRNA U2 and U6 are impacted by the presence of F. borealis U2AF2 and by AHCYL1, a specific partner of the divergent subunit U2AF2{beta}. In striking contrast with other species, F. borealis has lost m6A on the U6 snRNA while U1 snRNA has gained a stable, 5-terminal m6A. We used structure prediction to show how these snRNA modifications could play decisive roles during the recognition of non-GT/AG introns. In conclusion, we argue that spliceosome function can be profoundly impacted by gene neofunctionalization and post-transcriptional modifications, without implying major changes to conserved genetic components.

molecular biology↗

bioRxiv2023

Pax37 gene function in Oikopleura dioica supports a neuroepithelial-like origin for its house-making Fol territory

Larvacean tunicates feature a spectacular innovation not seen in other animals - the trunk oikoplastic epithelium (OE). This epithelium produces a house, a large and complex extracellular structure used for filtering and concentrating food particles. Previously we have shown that several homeobox transcription factors may play a role in patterning the OE. Among these are two Pax3/7 duplicates that we named Pax37A and Pax37B. The vertebrate homologs, PAX3 and PAX7, are involved in developmental processes related to neural crest and muscles. In the ascidian tunicate Ciona robusta, Pax3/7 has been given a role in development of cells deriving from the neural plate border including trunk epidermal sensory neurons and tail nerve cord neurons as well as in neural tube closure. Here we have investigated the roles of Pax37A and Pax37B in the development of the OE using CRISPR-Cas9, analyzing scRNA-seq data from wild-type animals that were compared with scRNA-seq data from C. robusta. We revealed that Pax37B but not Pax37A is essential for the differentiation of cell fields that produce the food concentrating filter of the house: the anterior Fol, giant Fol and Nasse cells. Lineage analysis supports that expression of Pax37 is under influence of Wnt signaling and that Fol cells have a neuroepithelial-like transcriptional signature. We propose that the highly specialized secretory epithelial cells of the Fol region either maintained or evolved neuroepithelial features as do "glue" secreting collocytes of ascidians. Their development seems to be controlled by a GRN that also operates in some ascidian neurons.

developmental biology↗

bioRxiv2022

Laboratory study of Fritillaria lifecycle reveals larvacean commonalities and key morphogenetic events leading to taxon-specific anatomy

A fascinating variety of adult body plans can be found in the Tunicates, the closest existing relatives of vertebrates. A distinctive feature of the larvacean class of pelagic tunicates is the presence of a highly specialized surface epithelium that produces a cellulose test, the "larvacean house". While substantial differences exist between the anatomy of larvacean families, most of the ontogeny is derived from the observations of a single genus, Oikopleura. We present the first study of Fritillaria development based on the observation of individuals reproduced in the laboratory. Like the other small epipelagic species Oikopleura dioica, the larvae of Fritillaria borealis grow rapidly in the laboratory, and they acquire the adult form within a day. We could show that major morphological differences exhibited by Fritillaria and Oikopleura adults originate from a key developmental stage during larval organogenesis. Here, the surface epithelium progressively retracts from the posterior digestive organs of Fritillaria larvae, and it establishes house-producing territories around the pharynx. Our results show that the divergence between larvacean genera was associated with a profound rearrangement of the mechanisms controlling the differentiation of the larval ectoderm.

zoology↗

bioRxiv2020

Conservative route to extreme genome compaction in a miniature annelid

The causes and consequences of genome reduction in animals are unclear, because our understanding of this process mostly relies on lineages with often exceptionally high rates of evolution. Here, we decode the compact 73.8 Mb genome of Dimorphilus gyrociliatus, a meiobenthic segmented worm. The D. gyrociliatus genome retains traits classically associated with larger and slower-evolving genomes, such as an ordered, intact Hox cluster, a generally conserved developmental toolkit, and traces of ancestral bilaterian linkage. Unlike some other animals with small genomes, the analysis of the D. gyrociliatus epigenome revealed canonical features of genome regulation, excluding the presence of operons and trans-splicing. Instead, the gene dense D. gyrociliatus genome presents a divergent Myc pathway, a key physiological regulator of growth, proliferation, and genome stability in animals. Altogether, our results uncover a conservative route to genome compaction in annelids, reminiscent of that observed in the vertebrate Takifugu rubripes.

genomics↗

bioRxiv2019

Surveillance-embedded genomic outbreak resolution of methicillin-susceptible Staphylococcus aureus in a neonatal intensive care unit

BackgroundWe observed an increase in methicillin-susceptible Staphylococcus aureus (MSSA) infections among neonates at a Dutch third level neonatal intensive care unit. Weekly surveillance data of MSSA carriage among neonates and cross-sectional screenings of health care workers (HCWs) were available for outbreak tracing. While traditional typing of MSSA isolates by staphylococcal protein A gene (spa typing) and Multiple-Locus Variable number tandem repeat Analysis (MLVA) suggested that nosocomial transmission had contributed to the infections, here they lacked the resolution to draw solid conclusions.\n\nMethodsMSSA isolates from neonatal infections, carriage surveillance, and HCWs were subjected to whole-genome sequencing and compared by a series of automated tools including de novo assembly, identification and localization of high-quality single nucleotide polymorphisms, and in-depth analysis of subsets of isolates. Outbreaks were defined as isolates that were more closely related than was to be expected from the genetic diversity in background surveillance.\n\nResultsGenomic analysis identified isolates that had been unjustly assigned to clusters based on MLVA typing, while spa typing was concordant but of insufficient resolution. Detailing particular subsets of isolates further improved resolution and although it provided evidence that HCWs were involved in multiple outbreaks, it alleviated heavy concerns about one particular HCW. Genomic clustering of isolates based on deviations from background surveillance matched epidemiological patient linkage. Compared to MLVA typing, the genomic analysis demonstrated more, shorter, and re-assorted nosocomial transmission chains during this outbreak.\n\nConclusionsIn this study the improved resolution and accuracy of genomic outbreak analyses compared to spa typing and MLVA substantially altered the view on outbreaks, along with apposite outbreak measures. Inclusion of the circulating background population has the potential to overcome current issues in genomic outbreak inference.

microbiology↗