Biology subjects

Cahill, J. A.

Publications and source records attributed to Cahill, J. A..

5 recordsLinked to original sources

bioRxiv2026

The Paipu framework enables creation of a large-scale mammalian cancer transcriptomics atlas

A plethora of studies have identified shared molecular mechanisms involved in tumor development across humans and other mammalian species. While these two-species analyses advance understanding of human disease, extending them across many species would provide evolutionary insight into molecular mechanisms driving human cancers. However, this expansion requires knowledge transfer and harmonization across species. Genomic differences between species, including variation in genome annotation quality, have historically hindered multi-species large-scale atlas creation. To overcome these challenges, we present Paipu, a comprehensive pipeline designed to streamline querying, preprocessing, harmonization, and retrieval of large-scale RNA-seq data and associated metadata from the NCBI Sequence Read Archive (SRA). Paipu facilitates multi-species analysis by creating a harmonized atlas from user-defined search terms and species. It consists of three components: reference genome preparation, SRA metadata retrieval, and RNA-seq data processing. We apply Paipu to 188 cancer-related terms in 239 non-human mammalian species, creating a harmonized atlas of 3,484 RNA-seq samples spanning 17 species and 35 cancers. This pan-mammalian pan-cancer atlas enables myriad comparative genomics analyses that leverage genetic variation to better understand rare human cancers. As such, Paipu serves as a resource for cross-species cancer genomics and supports atlas creation for any set of species and search terms. Graphical Abstract

bioinformatics↗

bioRxiv2018

Mountain lion genomes provide insights into genetic rescue of inbred populations

Introduction paragraph/AbstractAcross the geographic range of mountain lions, which includes much of North and South America, populations have become increasingly isolated due to human persecution and habitat loss. To explore the genomic consequences of these processes, we assembled a high-quality mountain lion genome and analyzed a panel of resequenced individuals from across their geographic range. We found strong geographical structure and signatures of severe inbreeding in all North American populations. Tracts of homozygosity were rarely shared among populations, suggesting that assisted gene flow would restore local genetic diversity. However, the genome of an admixed Florida panther that descended from a translocated individual from Central America had surprisingly long tracts of homozygosity, indicating that genomic gains from translocation were quickly lost by local inbreeding. Thus, to sustain diversity, genetic rescue will need to occur at regular intervals, through repeated translocations or restoring landscape connectivity. Mountain lions provide a rare opportunity to examine the potential to restore diversity through genetic rescue, and to observe the long-term effects of translocation. Our methods and results provide a framework for genome-wide analyses that can be applied to the management of small and isolated populations.

evolutionary biology↗

bioRxiv2017

Genomic evidence of globally widespread admixture from polar bears into brown bears during the last ice age

Recent genomic analyses have provided substantial evidence for past periods of gene flow from polar bears (Ursus maritimus) into Alaskan brown bears (Ursus arctos), with some analyses suggesting a link between climate change and genomic introgression. However, because it has only been possible to sample bears from the present day, the timing, frequency, and evolutionary significance of this admixture remains unknown. Here, we analyze genomic DNA from three additional and geographically distinct brown bear populations, including two that lived temporally close to the peak of the last ice age. We find evidence of admixture in all three populations, suggesting that admixture between these species has been common in their recent evolutionary history. In addition, analyses of ten fossil bears from the now-extinct Irish population indicate that admixture peaked during the last ice age, when brown bear and polar bear ranges overlapped. Following this peak, the proportion of polar bear ancestry in Irish brown bears declined rapidly until their extinction. Our results support a model in which ice age climate change created geographically widespread conditions conducive to admixture between polar bears and brown bears, as is again occurring today. We postulate that this model will be informative for many admixing species pairs impacted by climate change. Our results highlight the power of paleogenomes to reveal patterns of evolutionary change that are otherwise masked with only contemporary data.

evolutionary biology↗

bioRxiv2017

A new genus of horse from Pleistocene North America

The extinct \"New World stilt-legged\", or NWSL, equids constitute a perplexing group of Pleistocene horses endemic to North America. Their slender distal limb bones resemble those of Asiatic asses, such as the Persian onager. Previous palaeogenetic studies, however, have suggested a closer relationship to caballine horses than to Asiatic asses. Here, we report complete mitochondrial and partial nuclear genomes from NWSL equids from across their geographic range. Although multiple NWSL equid species have been named, our palaeogenomic and morphometric analyses support the idea that there was only a single species of middle to late Pleistocene NWSL equid, and demonstrate that it falls outside of crown group Equus. We therefore propose a new genus, Haringtonhippus, for the sole species H. francisci. Our combined genomic and phenomic approach to resolving the systematics of extinct megafauna will allow for an improved understanding of the full extent of the terminal Pleistocene extinction event.

paleontology↗

bioRxiv2017

Natural selection shaped the rise and fall of passenger pigeon genomic diversity

The extinct passenger pigeon was once the most abundant bird in North America, and possibly the world. While theory predicts that large populations will be more genetically diverse and respond more efficiently to selection, passenger pigeon genetic diversity was surprisingly low. To investigate this we analysed 41 mitochondrial and 4 nuclear genomes from passenger pigeons, and 2 genomes from band-tailed pigeons, passenger pigeons closest living relatives. We find that passenger pigeons large population size allowed for faster adaptive evolution and removal of harmful mutations, but that this drove a huge loss in neutral genetic diversity. These results demonstrate how great an impact selection can have on a vertebrate genome, and invalidate previous results that suggested population instability contributed to this species surprisingly rapid extinction.

genomics↗