Graham M. Hughes

A Novel Method of Microsatellite Genotyping-By-Sequencing Using Individual Combinatorial Barcoding

This study examines the potential of next-generation sequencing based ‘genotyping-by-sequencing’ (GBS) of microsatellite loci for rapid and cost-effective genotyping in large-scale population genetic studies. The recovery of individual genotypes from large sequence pools was achieved by PCR-incorporated combinatorial barcoding using universal primers. Three experimental conditions were employed to explore the possibility of using this approach with existing and novel multiplex marker panels and weighted amplicon mixture. The GBS approach was validated against microsatellite data generated by capillary electrophoresis. GBS allows access to the underlying nucleotide sequences that can reveal homoplasy, even in large datasets and facilitates cross laboratory transfer. GBS of microsatellites, using individual combinatorial barcoding, is potentially faster and cheaper than current microsatellite approaches and offers better and more data.

Loss of olfactory receptor function in hominin evolution.

The mammalian sense of smell is governed by the largest gene family, which encodes the olfactory receptors (ORs). The gain and loss of OR genes is typically correlated with adaptations to various ecological niches. Modern humans have 853 OR genes but 55% of these have lost their function. Here we show evidence of additional OR loss of function in the Neanderthal and Denisovan hominin genomes using comparative genomic methodologies. Ten Neanderthal and 8 Denisovan ORs show evidence of loss of function that differ from the reference modern human OR genome. Some of these losses are also present in a subset of modern humans, while some are unique to each lineage. Morphological changes in the cranium of Neanderthals suggest different sensory arrangements to that of modern humans. We identify differences in functional olfactory receptor genes among modern humans, Neanderthals and Denisovans, suggesting varied loss of function across all three taxa and we highlight the utility of using genomic information to elucidate the sensory niches of extinct species.

Using Illumina next generation sequencing technologies to sequence multigene families in de novo species

The advent of Next Generation Sequencing Technology (NGST) has revolutionized molecular biology research, allowing for rapid gene/genome sequencing from a multitude of diverse species. As high throughput sequencing becomes more accessible, more efficient workflows must be developed to deal with the amounts of data produced and better assemble the genomes of de novo lineages. We combine traditional laboratory methods with Illumina NGST to amplify and sequence the largest mammalian multigene family, the Olfactory Receptor gene family, for species with and without a reference genome. We develop novel assembly methods to annotate and filter these data, which can be utilized for any gene family or any species. We find no significant difference between the ratio of genes within their respective gene families of our data compared with available genomic data. Using simulated data we explore the limitations of short‐read sequence data and our assembly in recovering this gene family. We highlight the benefits and shortcomings of these methods. Compared with data generated from traditional polymerase chain reaction, cloning and Sanger sequencing methodologies, sequence data generated using our pipeline increases yield and sequencing efficiency without reducing the number of unique genes amplified. A cloning step is not required, therefore shortening data generation time. The novel downstream methodologies and workflows described provide a tool to be utilized by many fields of biology, to access and analyze the vast quantities of data generated. By combining laboratory and in silico methods, we provide a means of extracting genomic information for multigene families without complete genome sequencing.

Genome-wide signatures of complex introgression and adaptive evolution in the big cats

Big cat genomes reveal a history of interspecies admixture and adaptive evolution of genes underlying development and sensory perception. The great cats of the genus Panthera comprise a recent radiation whose evolutionary history is poorly understood. Their rapid diversification poses challenges to resolving their phylogeny while offering opportunities to investigate the historical dynamics of adaptive divergence. We report the sequence, de novo assembly, and annotation of the jaguar (Panthera onca) genome, a novel genome sequence for the leopard (Panthera pardus), and comparative analyses encompassing all living Panthera species. Demographic reconstructions indicated that all of these species have experienced variable episodes of population decline during the Pleistocene, ultimately leading to small effective sizes in present-day genomes. We observed pervasive genealogical discordance across Panthera genomes, caused by both incomplete lineage sorting and complex patterns of historical interspecific hybridization. We identified multiple signatures of species-specific positive selection, affecting genes involved in craniofacial and limb development, protein metabolism, hypoxia, reproduction, pigmentation, and sensory perception. There was remarkable concordance in pathways enriched in genomic segments implicated in interspecies introgression and in positive selection, suggesting that these processes were connected. We tested this hypothesis by developing exome capture probes targeting ~19,000 Panthera genes and applying them to 30 wild-caught jaguars. We found at least two genes (DOCK3 and COL4A5, both related to optic nerve development) bearing significant signatures of interspecies introgression and within-species positive selection. These findings indicate that post-speciation admixture has contributed genetic material that facilitated the adaptive evolution of big cat lineages.

Systematic exploration of guide-tree topology effects for small protein alignments

BackgroundGuide-trees are used as part of an essential heuristic to enable the calculation of multiple sequence alignments. They have been the focus of much method development but there has been little effort at determining systematically, which guide-trees, if any, give the best alignments. Some guide-tree construction schemes are based on pair-wise distances amongst unaligned sequences. Others try to emulate an underlying evolutionary tree and involve various iteration methods.ResultsWe explore all possible guide-trees for a set of protein alignments of up to eight sequences. We find that pairwise distance based default guide-trees sometimes outperform evolutionary guide-trees, as measured by structure derived reference alignments. However, default guide-trees fall way short of the optimum attainable scores. On average chained guide-trees perform better than balanced ones but are not better than default guide-trees for small alignments.ConclusionsAlignment methods that use Consistency or hidden Markov models to make alignments are less susceptible to sub-optimal guide-trees than simpler methods, that basically use conventional sequence alignment between profiles. The latter appear to be affected positively by evolutionary based guide-trees for difficult alignments and negatively for easy alignments. One phylogeny aware alignment program can strongly discriminate between good and bad guide-trees. The results for randomly chained guide-trees improve with the number of sequences.

Growing old, yet staying young: The role of telomeres in bats’ exceptional longevity

Telomeres do not shorten with age in longest-lived bats. Understanding aging is a grand challenge in biology. Exceptionally long-lived animals have mechanisms that underpin extreme longevity. Telomeres are protective nucleotide repeats on chromosome tips that shorten with cell division, potentially limiting life span. Bats are the longest-lived mammals for their size, but it is unknown whether their telomeres shorten. Using >60 years of cumulative mark-recapture field data, we show that telomeres shorten with age in Rhinolophus ferrumequinum and Miniopterus schreibersii, but not in the bat genus with greatest longevity, Myotis. As in humans, telomerase is not expressed in Myotis myotis blood or fibroblasts. Selection tests on telomere maintenance genes show that ATM and SETX, which repair and prevent DNA damage, potentially mediate telomere dynamics in Myotis bats. Twenty-one telomere maintenance genes are differentially expressed in Myotis, of which 14 are enriched for DNA repair, and 5 for alternative telomere-lengthening mechanisms. We demonstrate how telomeres, telomerase, and DNA repair genes have contributed to the evolution of exceptional longevity in Myotis bats, advancing our understanding of healthy aging.

The Birth and Death of Olfactory Receptor Gene Families in Mammalian Niche Adaptation

Abstract The olfactory receptor (OR) gene families, which govern mammalian olfaction, have undergone extensive expansion and contraction through duplication and pseudogenization. Previous studies have shown that broadly defined environmental adaptations (e.g., terrestrial vs. aquatic) are correlated with the number of functional and non‐functional OR genes retained. However, to date, no study has examined species‐specific gene duplications in multiple phylogenetically divergent mammals to elucidate OR evolution and adaptation. Here, we identify the OR gene families driving adaptation to different ecological niches by mapping the fate of species‐specific gene duplications in the OR repertoire of 94 diverse mammalian taxa, using molecular phylogenomic methods. We analyze >70,000 OR gene sequences mined from whole genomes, generated from novel amplicon sequencing data, and collated with data from previous studies, comprising one of the largest OR studies to date. For the first time, we demonstrate statistically significant patterns of OR species‐specific gene duplications associated with the presence of a functioning vomeronasal organ. With respect to dietary niche, we uncover a novel link between a large number of duplications in OR family 5/8/9 and herbivory. Our results also highlight differences between social and solitary niches, indicating that a greater OR repertoire expansion may be associated with a solitary lifestyle. This study demonstrates the utility of species‐specific duplications in elucidating gene family evolution, revealing how the OR repertoire has undergone expansion and contraction with respect to a number of ecological adaptations in mammals.

Is there a link between aging and microbiome diversity in exceptional mammalian longevity

A changing microbiome has been linked to biological aging in mice and humans, suggesting a possible role of gut flora in pathogenic aging phenotypes. Many bat species have exceptional longevity given their body size and some can live up to ten times longer than expected with little signs of aging. This study explores the anal microbiome of the exceptionally long-lived Myotis myotis bat, investigating bacterial composition in both adult and juvenile bats to determine if the microbiome changes with age in a wild, long-lived non-model organism, using non-lethal sampling. The anal microbiome was sequenced using metabarcoding in more than 50 individuals, finding no significant difference between the composition of juvenile and adult bats, suggesting that age-related microbial shifts previously observed in other mammals may not be present in Myotis myotis. Functional gene categories, inferred from metabarcoding data, expressed in the M. myotis microbiome were categorized identifying pathways involved in metabolism, DNA repair and oxidative phosphorylation. We highlight an abundance of ‘Proteobacteria’ relative to other mammals, with similar patterns compared to other bat microbiomes. Our results suggest that M. myotis may have a relatively stable, unchanging microbiome playing a role in their extended ‘health spans’ with the advancement of age, and suggest a potential link between microbiome and sustained, powered flight.

A potent anti-inflammatory response in bat macrophages may be linked to extended longevity and viral tolerance

Bats are unique among mammals given their ability to fly, apparent tolerance of deadly viruses and extraordinary longevity. We propose that these traits are linked and driven by adaptations of the innate immune system. To explore this hypothesis we challenged macrophages from the greater mouse-eared bat, Myotis myotis and the house mouse, Mus musculus with toll like receptors (TLRs) ligands, lipopolysaccharides, LPS and polyinosinic-polycytidylic acid, Poly(I:C). Macrophages from both species presented a high level of mRNA induction of inferon β (INF-β), tumor necrosis factor (TNF) and interleukin-1β (Il-1β). However, in bat macrophages, this antiviral, proinflammatory response was balanced by a sustained high-level transcription of the anti-inflammatory cytokine Il-10, which was not observed in mouse, potentially resulting from adaptive regulation in bats. Additionally, phylogenomic selection tests across the basal divergences in mammals (n = 39) uncovered bat-specific adaptations in six genes involved in antiviral and proinflammatory signalling. Based on this pilot study, we put forward a hypothesis that bats may have evolved unique anti-inflammatory responses to neutralize proinflammatory stimuli resulting from flight. This in turn may drive their extraordinary longevity and viral tolerance by limiting inflammation driven ageing and infection-induced immunopathology. Further data from other individuals and bat species are required to advance this intriguing hypothesis.

AGILE: an assembled genome mining pipeline

SUMMARY A number of limiting factors mean that traditional genome annotation tools either fail or perform sub-optimally when trying to detect coding sequences in poor quality genome assemblies/genome reports. This means that potentially useful data is accessible only to those with specific skills and expertise in assembly and annotation. We present an Assembled-Genome mIning pipeLinE (AGILE) written in Perl that combines bioinformatics tools with a number of steps to overcome the limitations imposed by such assemblies when applied to highly fragmented genomes. Our methodology uses user-specified query genes from a closely related species to mine and annotate coding sequences that would traditionally be missed by standard annotation packages. Despite a focus on mammalian genomes, the generalized implementation means that it may be applied to any genome assembly, providing a means for non-specialists to gather gene sequences for downstream analyses. AVAILABILITY AND IMPLEMENTATION Source code and associated files are available at: https://github.com/batlabucd/GenomeMining and https://bitbucket.org/BatlabUCD/genomemining/src. Singularity and Virtual Box images available at https://figshare.com/s/a0004bf93dc43484b0c0. SUPPLEMENTARY INFORMATION Supplementary data are available at Bioinformatics online.