Biology subjects

Elsik, C. G.

Publications and source records attributed to Elsik, C. G..

5 recordsLinked to original sources

bioRxiv2025

A pangenome framework uncovers the role of deletions in repeated evolution of cave-derived traits

Structural variants (SVs) are increasingly recognized as key contributors to adaptive evolution, yet they remain underexplored compared to single-nucleotide variation. To understand how large-scale genomic changes shape repeated evolution, we leveraged multiple levels of sequence data across the powerful evolutionary model system of the Mexican tetra fish (Astyanax mexicanus). Cavefish populations have repeatedly evolved similar and dramatic phenotypes compared to surface fish such as eye loss, pigmentation loss, and sleep loss, suggesting a potential role for loss-of-function variants in cave adaptation. We constructed one of the first pangenome graphs from a naturally evolving vertebrate, enabling comprehensive discovery of SVs among 120 fish from 11 populations. We identified over 2,400 high-confidence cave-specific deletions that are enriched in biological pathways involved in vision, metabolism, and behavior and cluster non-randomly in quantitative trait loci linked to cavefish traits. Strikingly, 67 genes harbor unique deletions between independent cavefish lineages. These reused genes show strong evidence of population-specific selection (99% are under selection, compared to 8-15% in genes lacking SVs), indicating that deletions rose in frequency through repeated positive selection rather than drift. Together, these results reveal that recurrent deletion events have repeatedly contributed to the evolution of cave-adapted phenotypes and highlight deletions as underexplored contributors of adaptive evolution in a system characterized by trait loss.

evolutionary biology↗

bioRxiv2022

Identification of large offspring syndrome during pregnancy through ultrasonography and maternal blood transcriptome analyses

The use of assisted reproductive technologies (ART) in cattle can result in large/abnormal offspring syndrome (LOS/AOS) which is characterized by macrosomia. LOS can cause dystocia and lead to the death of dam and calf. Currently, no test exists to identify LOS pregnancies. We hypothesized that fetal ultrasonography and/or maternal blood markers are useful to identify LOS. Bovine fetuses were generated by artificial insemination (control) or ART. Fetal ultrasonographies were taken on gestation day 55 (D55) and fetal collections performed on D56 or D105 (gestation in cattle {approx}280 days). ART fetuses weighing [≥]97 percentile of the control weight were considered LOS. Ultrasonography results show that the product of six D55 measurements can be used to identify extreme cases of LOS. To determine whether maternal blood can be used to identify LOS, leukocyte mRNA from 23 females was sequenced. Unsupervised hierarchical clustering grouped the transcriptomes of the two females carrying the two largest LOS fetuses. Comparison of the leukocyte transcriptomes of these two females to the transcriptome of all other females identified several misregulated transcripts on gestation D55 and D105 with LOC783838 and PCDH1 being misregulated at both time-points. Together our data suggest that LOS is identifiable during pregnancy in cattle.

developmental biology↗

bioRxiv2021

Nuclear Translocation of Vitellogenin in the Honey Bee (Apis mellifera)

Vitellogenin (Vg) is a conserved protein used by nearly all oviparous animals to produce eggs. It is also pleiotropic and performs functions in oxidative stress resistance, immunity, and, in honey bees, behavioral development of the worker caste. It has remained enigmatic how Vg affects multiple traits. Here, we asked whether Vg enters the nucleus and acts via DNA-binding. We used immunohistology, cell fractionation and cell culturation to show that a structural subunit of honey bee Vg translocates into cell nuclei. We then demonstrated Vg-DNA binding theoretically and empirically with prediction software and chromatin immunoprecipitation with sequencing (ChIP-seq), finding binding sites at genes influencing immunity and behavior. Finally, we investigated the immunological and enzymatic conditions affecting Vg cleavage and nuclear translocation, and constructed a 3D structural model. Our data are the first to show Vg in the nucleus and suggests a new fundamental regulatory role for this ubiquitous protein.

molecular biology↗

bioRxiv2020

Detection of alternative splicing in western corn rootworm (Diabrotica virgifera virgifera LeConte) in association with Bt resistance using RNA-seq and PacBio Iso-Seq

BackgroundAlternative splicing is one of the major mechanisms that increases transcriptome diversity in eukaryotes, including insect species that have gained resistance to pesticides and Bt toxins. In western corn rootworm (Diabrotica virgifera virgifera LeConte), neither alternative splicing nor its role in resistance to Bt toxins has been studied. ResultsTo investigate the mechanisms of Bt resistance we carried out single-molecule real-time (SMRT) transcript sequencing and Iso-seq analysis on resistant, eCry3.1Ab-selected and susceptible, unselected, western corn rootworm neonate midguts which fed on seedling maize with and without eCry3.1Ab for 12 and 24 hours. We present transcriptome-wide alternative splicing patterns of western corn rootworm midgut in response to feeding on eCry3.1Ab-expressing corn using a comprehensive approach that combines both RNA-seq and SMRT transcript sequencing techniques. We found that 67.73% of multi-exon genes are alternatively spliced, which is consistent with the high transposable element content of the genome. One of the alternative splicing events we identified was a novel peritrophic matrix protein with two alternative splicing isoforms. Analysis of differential exon usage between resistant and susceptible colonies showed that in eCry3.1Ab-resistant western corn rootworm, expression of one isoform was significantly higher than in the susceptible colony, while no significant differences between colonies were observed with the other isoform. ConclusionOur results provide the first survey of alternative splicing in western corn rootworm and suggest that the observed alternatively spliced isoforms of peritrophic matrix protein may be associated with eCry3.1Ab resistance in western corn rootworm.

genomics↗

bioRxiv2020

Cat fleas in flux: Rampant gene duplication, genome size plasticity, and paradoxical Wolbachia infection

BackgroundFleas (Insecta: Siphonaptera) are small flightless parasites of birds and mammals; their blood-feeding can transmit many serious pathogens (i.e. the etiological agents of bubonic plague, endemic and murine typhus). The lack of flea genome assemblies has hindered research, especially comparisons to other disease vectors. Accordingly, we sequenced the genome of the cat flea, Ctenocephalides felis, an insect with substantial human health and veterinary importance across the globe. ResultsBy combining Illumina and PacBio sequencing with Hi-C scaffolding techniques, we generated a chromosome-level genome assembly for C. felis. Unexpectedly, our assembly revealed extensive gene duplication across the entire genome, exemplified by [~]38% of protein-coding genes with two or more copies and over 4,000 tRNA genes. A broad range of genome size determinations (433-551 Mb) for individual fleas sampled across different populations supports the widespread presence of fluctuating copy number variation (CNV) in C. felis. Similarly broad genome sizes were also calculated for individuals of Xenopsylla cheopis (Oriental rat flea), indicating that this remarkable "genome-in-flux" phenomenon could be a siphonapteran-wide trait. Finally, from the C. felis sequence reads we also generated closed genomes for two novel strains of Wolbachia, one parasitic and one symbiotic, found to co-infect individual fleas. ConclusionRampant CNV in C. felis has dire implications for gene-targeting pest control measures and stands to complicate standard normalization procedures utilized in comparative transcriptomics analysis. Coupled with co-infection by novel Wolbachia endosymbionts - potential tools for blocking pathogen transmission - these oddities highlight a unique and underappreciated disease vector.

genomics↗