Biology subjects

Hilgers, L.

Publications and source records attributed to Hilgers, L..

13 recordsLinked to original sources

bioRxiv2026

Sea stickleback genome reveals repeated chromosomal rearrangements in sticklebacks

Sticklebacks (Gasterosteidae) encompass model organisms which are of particular interest for evolutionary and ecological genomics. Within Gasterosteidae, chromosome number is variable (2n=40-46) and independent fusions of homologous chromosomes have been proposed. The sea stickleback (or fifteen-spined stickleback, Spinachia spinachia ) has the lowest known number of chromosomes (2n=40) and hence is crucial in understanding chromosome evolution among sticklebacks, but is so far missing in genomic datasets. Here, we present a high-quality diploid genome assembly of S. spinachia. PacBio HiFi and Hi-C reads were assembled into a genome of 407.5 Mb in size, consisting of 20 chromosomes, with an N50 of 6.6 Mb and 98.96% complete single-copy BUSCO genes. A phylogenetic tree inferred across five stickleback species and four outgroup genomes from 19,156 genes, alongside synteny analyses and ancestral chromosome reconstructions, confirms S. spinachia as the sister species to the four-spined stickleback (Apeltes quadracus) and not as the sister group to all other sticklebacks as once thought. It has one species-specific chromosome fusion and shares two fusions with the three-spined stickleback (Gasterosteus aculeatus), none of which are present in its sister species. One of these fusions is also present in Pungitius, leading to reinterpretion of this fusion as ancestral to Gasterosteidae, with subsequent fission in Apeltes. This implies a lower ancestral chromosome number in Gasterosteidae (2n=44) than previously thought. The other fusion shared with G. aculeatus presents a case of convergence. Our results suggest that karyotype evolution in Gasterosteidae has been shaped by ancestral chromosome fusion, convergent fusion, and secondary fission.

evolutionary biology↗

bioRxiv2026

LiteVax-adjuvanted influenza vaccine induces transient interferon-driven innate activation and accelerates early IgG3 responses in older adults

Vaccine immunogenicity declines with age due to immunosenescence, underscoring the need for improved adjuvants. LiteVax Adjuvant (LVA), a squalane-in-water emulsion containing carbohydrate fatty-acid monosulphate esters, has shown potential to enhance influenza vaccine responses, but its mechanisms in humans remain unclear. We performed a longitudinal systems vaccinology study in 56 younger (18-45 years) and older ([≥]60 years) adults receiving a quadrivalent influenza vaccine with or without LVA. Multi-omics analyses, including bulk and single-cell transcriptomics, flow cytometry, and serology, revealed that LVA induced a rapid, transient interferon-driven innate response, primarily in monocytes, associated with enhanced antigen processing and dendritic cell to T cell interactions. LVA promoted differentiation of influenza-specific CD4+ T cells toward CD45RO+ memory phenotypes, accelerated early IgG3 antibody responses, and increased IgG-producing plasmablast frequencies without affecting overall antibody magnitude. Importantly, LVA reduced age-related differences in early immune responses, improving response quality and supporting vaccine performance in older adults.

immunology↗

bioRxiv2026

Integrated genomics and transcriptomics reveal mechanisms of extreme dietary adaptation in vampire bats

Vampire bats are the only tetrapods that feed exclusively on blood. To uncover the molecular basis of this extreme dietary specialization, we generated six new reference genomes, including genomes of all three vampire bat species, and integrated comparative analyses of gene sequence evolution (selection signatures, duplications, and losses) with transcriptomic data from six major organs to identify shifts in gene expression. Our integrative analyses reveal sequence or expression changes in 150 genes that illuminate the genetic mechanisms underlying sanguivory. Through comparative analyses and experiments, we show that the enlarged vampire bat stomach has increased connective tissue content enabling extreme expansion, is pH-neutral, and exhibits reduced mucus production, together providing molecular insights into its shift from a digestive to an absorptive organ for water, electrolytes, and vitamins. We further uncover pathway-level molecular changes underlying altered gastrointestinal motility; trypsin-dependent protein digestion; upregulated amino acid catabolism with key aspects diverging from other mammals; impaired dietary fat digestion counterbalanced by increased fatty acid synthesis; defective sugar metabolism and natural insulin deficiency; enhanced heme iron absorption; and adult splenic erythropoiesis. Together, these findings reveal the molecular adaptations that enable one of the most extreme dietary transitions among vertebrates.

evolutionary biology↗

bioRxiv2026

Accurate, comprehensive gene annotation and ortholog identification across thousands of vertebrate genomes with TOGA2

Inferring orthologs and annotating coding genes remain central challenges in genomics, evident by the growing gap between assembled and annotated genomes. TOGA (Tool to infer Orthologs from Genome Alignments) addresses this challenge by integrating gene annotation and orthology inference. Here, we present TOGA2, the next generation of TOGA, which substantially improves annotation completeness, accuracy, scalability, and orthology inference. TOGA2 leverages exon-level orthology and introduces an exon-wise annotation procedure that reduces memory usage 513-fold and runtime 6.1-fold. We show that human-trained deep learning models for splice site prediction generalize across vertebrates. Integrating these predictions enables robust handling of evolutionary changes in exon-intron structure, including splice site shifts, intron deletions, and exonization of introns. A new gene tree reconciliation step refines orthology inference, and UTR annotation improves gene model completeness. Across mammals, birds, turtles, and percomorph fishes, TOGA2 annotations generally achieve higher gene completeness than transcriptome-informed RefSeq annotations. TOGA2 identifies previously unannotated exons in mouse, assigns informative gene symbols, and annotates V(D)J segments of antigen receptors. TOGA2 scales to thousands of genomes, which we demonstrate by generating comprehensive comparative genomics resources for 2,162 vertebrate assemblies, including gene annotations, ortholog sets, gene losses and duplications, retrogene candidates, and outputs supporting downstream analyses. Together, TOGA2 provides a scalable and versatile framework for comparative genomics that bridges the genome annotation gap.

genomics↗

bioRxiv2026

Whole-genome phylogenomics and synteny resolve a single origin of body-plan asymmetry in flatfishes

Flatfishes display the most dramatic asymmetric body plan in vertebrates, yet whether this rare innovation evolved once (flatfish monophyly, FM) or multiple times (flatfish polyphyly, FP) has remained contentious. A recent genome-wide study supported FP by placing Psettodes, the earliest-diverging flatfish lineage, among symmetric relatives within Carangaria, the clade that also includes billfishes, jacks, mahi-mahi, and barracudas. Subsequent work traced this to base-composition artifacts and inadequate substitution modeling. Here we revisit the question using whole-genome phylogenomic and synteny data from 17 carangarian species spanning flatfishes and carangarian relatives. We contribute three new chromosome-level assemblies, including the first for Psettodes. Nucleotide-based coalescent analyses (e.g., ROADIES, CASTER) yield strong support for FM, with Psettodes sister to all other flatfishes. Microsynteny analyses built from conserved gene-order blocks corroborate this result: topology tests, cluster-profile counts, and rearrangement-based trees favor FM over two competing FP topologies. Macrosynteny, based on chromosome-scale rearrangements, yields a more mixed signal, with support for FM depending on the metric and taxon-sampling scheme. We interpret this scale-dependent pattern in the context of the explosive post-Cretaceous radiation of Carangaria. The short intervals between speciation events that characterize rapid radiations appear to have left sufficient signal in fine-grained microsyntenic rearrangements, while chromosome-scale rearrangements were too rare to consistently resolve these closely spaced splits. When integrated with evidence from conserved developmental mechanisms active during metamorphosis, the stage at which flatfish asymmetry first emerges, and from the exceptionally complete fossil record, our multi-scale genomic evidence supports a single evolutionary origin of flatfish asymmetry.

evolutionary biology↗

bioRxiv2026

Heterochrony of axis segmentation underlies extreme morphogenesis in the Japanese eel

Heterochrony is a major mode of vertebrate body plan evolution, yet its molecular and cellular basis remains poorly characterized. Here, we show that axis segmentation in Anguilla japonica--a species that forms 120 vertebrae--is driven by the temporal extension of somitogenesis. This is achieved through the prolonged maintenance of axial progenitors in the tail beyond the hatching stage, coupled to an extreme segment scaling regime that operates under the constraint of minimal axis growth. We identify delayed Hox13 activation and sustained Oct4 expression as molecular signatures of the prolonged segmentation program. Furthermore, we describe two spatially distinct axial progenitor pools that expand stemness in the tail. These findings reveal how the modulation of stemness in time and space drives extreme morphological evolution in vertebrates. One-Sentence SummarySpatiotemporal modulation of stemness drives extreme axis segmentation in the Japanese eel.

developmental biology↗

bioRxiv2026

Side-necked turtle genomes reveal chromosomal dynamics, skeletal innovation and cancer resistance

Turtles exhibit a highly derived body plan, exceptional longevity, cancer resistance, and striking diversity in karyotypes and sex determination systems. However, the genomic basis of these innovations remains unresolved, largely because reference genomes were lacking for one of two extant turtle clades, the side-necked turtles (Pleurodira). As part of the Vertebrate Genomes Project, we generated seven reference-quality Pleurodira genomes and reconstructed the most comprehensive genome-wide turtle phylogeny. Combining demographic inference with historical climate and biome reconstructions indicates that ancient climate fluctuations shaped long-term population dynamics, while recent declines mainly reflect population structure. Ancestral genome reconstructions reveal that rare bursts of chromosome fusions and fissions, likely facilitated by repetitive elements, drove turtle karyotype diversity. By identifying sex chromosomes and tracing their evolutionary history, we resolve a long-standing debate and demonstrate a single origin of genetic sex determination in Chelidae on a microchromosome over 80 million years ago. Contrary to previous hypotheses, we find no evidence of coevolution between genetic sex determination and chromosome number in turtles. Comparative genomic analyses further identify gene losses and signatures of adaptive evolution associated with key turtle traits. Gene losses causing disproportionate dwarfism phenotypes may have contributed to skeletal adaptations underlying the compact turtle body plan. In addition, gene losses and adaptive changes in stress response and tumor suppressor pathways likely enhance oxidative stress tolerance and cancer resistance. Together, these findings illuminate turtle genome evolution, revealing chromosomal dynamics, sex chromosome evolution, molecular insights into skeletal innovation and cancer resistance, and implicate gene losses as a recurrent contributor to evolutionary novelty.

genomics↗

bioRxiv2024

Avoidable false PSMC population size peaks occur across numerous studies

Inferring historical population sizes is key to identify drivers of ecological and evolutionary change, and crucial to predict the future of species on our rapidly changing planet. The pairwise sequentially Markovian coalescent (PSMC) method provided a revolutionary framework to reconstruct species demographic histories over millions of years based on the genome sequence of a single individual 1. Here, we detected and solved a common artifact in PSMC and related methods: recent population peaks followed by population collapses. Combining real and simulated genomes, we show that these peaks do not represent true population dynamics. Instead, ill-set default parameters cause false peaks in our own and published data, which can be avoided by adjusted parameter settings. Furthermore, we show that certain population structure changes can cause similar patterns. Newer methods like Beta-PSMC perform better, but do not always avoid this artifact. Our results suggest testing multiple parameters before interpreting recent population peaks followed by collapses, and call for the development of robust methods.

evolutionary biology↗

bioRxiv2024

Haplotype-resolved genome and population genomics of the threatened garden dormouse in Europe

Genomic resources are important for evaluating genetic diversity and supporting conservation efforts. The garden dormouse (Eliomys quercinus) is a small rodent that has experienced one of the most severe modern population declines in Europe. We present a high-quality haplotype-resolved reference genome for the garden dormouse, and combine comprehensive short and long-read transcriptomics datasets with homology-based methods to generate a highly complete gene annotation. Demographic history analysis of the genome revealed a sharp population decline since the last interglacial, indicating an association between colder climates and population declines prior to anthropogenic influence. Using our genome and genetic data from 100 individuals, largely sampled in a citizen-science project across the contemporary range, we conducted the first population genomic analysis for this species. We found clear evidence for population structure across the species core Central European range. Notably, our data shows that the Alpine population, characterized by strong differentiation and reduced genetic diversity, is reproductively isolated from other regions and likely represents a differentiated evolutionary significant unit (ESU). The predominantly declining Eastern European populations also show signs of recent isolation, a pattern consistent with a range expansion from Western to Eastern Europe during the Holocene, leaving relict populations now facing local extinction. Overall, our findings suggest that garden dormouse conservation may be enhanced in Europe through designation of ESUs.

genomics↗

bioRxiv2022

Integrating gene annotation with orthology inference at scale

Annotating coding genes and inferring orthologs are two classical challenges in genomics and evolutionary biology that have traditionally been approached separately, limiting scalability. We present TOGA, a method that integrates structural gene annotation and orthology inference. TOGA implements a different paradigm to infer orthologous loci, improves ortholog detection and annotation of conserved genes compared to state-of-the-art methods, and handles even highly-fragmented assemblies. TOGA scales to hundreds of genomes, which we demonstrate by applying it to 488 placental mammal and 501 bird assemblies, creating the largest comparative gene resources so far. Additionally, TOGA detects gene losses, enables selection screens, and automatically provides a superior measure of mammalian genome quality. Together, TOGA is a powerful and scalable method to annotate and compare genes in the genomic era.

genomics↗

bioRxiv2022

Contribution of hybridization to the evolution of a derived reproductive strategy in ricefishes

Transitions between reproductive strategies are costly and involve major changes in life history, behaviour and morphology. Nevertheless, in Sulawesi ricefishes, pelvic-brooding evolved from transfer-brooding in two distantly related lineages within in the genera Adrianichthys and in Oryzias, respectively. Females of pelvic-brooding species carry their eggs attached to their belly until the fry hatches. Despite their phylogenetic distance, both pelvic-brooding lineages share a set of external morphological traits. A recent study found no direct gene-flow between pelvic-brooding lineages suggesting independent evolution of the derived reproductive strategy. It could, however, also be more complex. Pre-existing variation in an admixed population may enable the re-use of genetic variants when subjected to similar external selection pressure, resulting in similar phenotypes. We thus used a multi-species coalescent (MSC) model and D-statistics to identify gene-tree - species-tree incongruencies, to evaluate the evolution of pelvic-brooding with respect to inter-specific gene-flow not only between pelvic-brooding lineages, but between pelvic-brooding lineages and other Sulawesi ricefish lineages. We found a general network-like evolution in Sulawesi ricefishes and as previously reported, no gene-flow between the pelvic-brooding lineages. Instead, we found hybridization between the ancestor of pelvic-brooding Oryzias and the common ancestor of the four Oryzias species from Lake Poso, home of the pelvic-brooding Adrianichthys lineage. Further, indications of introgression were located within two confidence intervals of quantitative trait loci (QTL) associated with pelvic-brooding in O. eversi. We thus hypothesize that a mix of de novo mutations and (ancient) standing genetic variation shaped the evolution of pelvic-brooding. Significance statementThe evolution of pelvic-brooding in Oryzias eversi (Beloniformes:Adrianichthyidae), was recently described to be independent from another pelvic-brooding ricefish lineage (Adrianichthys) from Sulawesi. We confirmed these results, and detected no gene flow between the two distantly related pelvic-brooding lineages. Instead, we found ancient gene flow from another Orzyias lineage into the pelvic-brooding Oryzias lineage. One of the previously described QTL for pelvic brooding overlaps with a region of high introgression signal. Therefore, we assume that not only de novo mutations contributed to the evolution of pelvic-brooding in Orzyias, but that introduced ancient genetic variation was likely also recruited for the evolution of this derived brooding strategy.

evolutionary biology↗

bioRxiv2021

An adjuvanted SARS-CoV-2 RBD nanoparticle elicits neutralizing antibodies and fully protective immunity in aged mice

Development of affordable and effective vaccines that can also protect vulnerable populations such as the elderly from COVID-19-related morbidity and mortality is a public health priority. Here we took a systematic and iterative approach by testing several SARS-CoV-2 protein antigens and adjuvants to identify a combination that elicits neutralizing antibodies and protection in young and aged mice. In particular, SARS-CoV-2 receptorbinding domain (RBD) displayed as a protein nanoparticle (RBD-NP) was a highly effective antigen, and when formulated with an oil-in-water emulsion containing Carbohydrate fatty acid MonoSulphate derivative (CMS) induced the highest levels of cross-neutralizing antibodies compared to other oil-in-water emulsions or AS01B. Mechanistically, CMS induced antigen retention in the draining lymph node (dLN) and expression of cytokines, chemokines and type I interferon-stimulated genes at both injection site and dLN. Overall, CMS:RBD-NP is effective across multiple age groups and is an exemplar of a SARS-CoV-2 subunit vaccine tailored to the elderly.

immunology↗

bioRxiv2020

Radula diversification promotes ecomorph divergence in an adaptive radiation of freshwater snails

Adaptive diversification of complex traits plays a pivotal role for the evolution of organismal diversity. However, the underlying molecular mechanisms remain largely elusive. In the freshwater snail genus Tylomelania, adaptive radiations were likely promoted by trophic specialization via diversification of their key foraging organ, the radula. To investigate the molecular basis of radula diversification and its contribution to lineage divergence, we use pooled tissue-specific transcriptomes of two sympatric Tylomelania sarasinorum ecomorphs. We show that divergence in both gene expression and coding sequences is stronger between radula transcriptomes compared to mantle and foot transcriptomes. These findings support the hypothesis that diversifying selection on the radula is driving speciation in Tylomelania radiations. We also identify several candidate genes for radula divergence. Putative homologs of some candidates (hh, arx, gbb) also contributed to trophic specialization in cichlids and Darwins finches, indicating that some molecular pathways may be especially prone to adaptive diversification.

evolutionary biology↗