Biology subjects

George H Perry

Publications and source records attributed to George H Perry.

3 recordsLinked to original sources

bioRxiv2016

A massively parallel strategy for STR marker development, capture, and genotyping

Short tandem repeat (STRs or microsatellites) variants, are highly polymorphic markers that facilitate powerful, high-precision population genetic analyses. STRs are especially valuable in conservation and ecological genetic research, yielding detailed information on population structure and short-term demographic flux. However, STR marker development and analysis by conventional PCR-based methods imposes a workflow bottleneck and is suboptimal for noninvasive sampling strategies such as fecal DNA recovery. While massively parallel sequencing has not previously been leveraged for scalable, efficient STR recovery, here we present a pipeline for developing STR markers directly from high-throughput shotgun sequencing data without requiring a reference genome assembly, and a methodological approach for highly parallel recovery of enriched STR loci. We first employed our approach to design and capture a panel of 5,000 STR loci from a test group of diademed sifakas (Propithecus diadema, n=3), endangered Malagasy rainforest lemurs, and we report extremely efficient recovery of targeted loci--97.3-99.6% of STRs characterized with [≥]10x non-redundant coverage. Second, we tested our STR capture strategy on a P. diadema fecal DNA preparation, and report robust initial results and methodological suggestions for future implementations. In addition to STR targets, this approach also generates large, genome-wide single nucleotide polymorphism (SNP) panels from regions flanking the STR loci. Our method provides a cost-effective and highly scalable solution for rapid recovery of large STR and SNP datasets in any species without need for a reference genome, and can be used even with suboptimal DNA, which is more easily acquired in conservation and ecological genetic studies.\n\nData DepositionRaw sequencing data are available under Study Accession numbers SRP073167 (genomic shotgun data for Oberon and Tatiana) and SRP076225 (targeted re-sequencing data) from the NCBI Sequence Read Archive. BaitSTR software is available at Github (core BaitSTR programs: https://github.com/aakrosh/BaitSTR; BaitSTR_type.pl companion script for genotyping and block manipulation: https://github.com/lkistler/BaitSTR_type).

Genomics↗

bioRxiv2016

Do aye-ayes echolocate? Studying convergent genomic evolution in a primate auditory specialist

Several taxonomically distinct mammalian groups - certain microbats and cetaceans (e.g. dolphins) - share both morphological adaptations related to echolocation behavior and strong signatures of convergent evolution at the amino acid level across seven genes related to auditory processing. Aye-ayes (Daubentonia madagascariensis) are nocturnal lemurs with a derived auditory processing system. Aye-ayes tap rapidly along the surfaces of dead trees, listening to reverberations to identify the mines of wood-boring insect larvae; this behavior has been hypothesized to functionally mimic echolocation. Here we investigated whether there are signals of genomic convergence between aye-ayes and known mammalian echolocators. We developed a computational pipeline (BEAT: Basic Exon Assembly Tool) that produces consensus sequences for regions of interest from shotgun genomic sequencing data for non-model organisms without requiring de novo genome assembly. We reconstructed complete coding region sequences for the seven convergent echolocating bat-dolphin genes for aye-ayes and another lemur. Sequences were compared in a phylogenetic framework to those of bat and dolphin echolocators and appropriate non-echolocating outgroups. Our analysis reaffirms the existence of amino acid convergence at these loci among echolocating bats and dolphins; we also detected unexpected signals of convergence between echolocating bats and both mice and elephants. However, we observed no significant signal of amino acid convergence between aye-ayes and echolocating bats and dolphins; our results thus suggest that aye-aye tap-foraging auditory adaptations represent distinct evolutionary innovations. These results are also consistent with a developing consensus that convergent behavioral ecology is not necessarily a reliable guide to convergent molecular evolution.

Evolutionary Biology↗

bioRxiv2016

An evolutionary medicine perspective on Neandertal extinction

The Eurasian sympatry of Neandertals and anatomically modern humans - beginning at least 45,000 years ago and lasting for more than 5,000 years - has long sparked anthropological interest into the factors that potentially contributed to Neandertal extinction. Among many different hypotheses, the \"differential pathogen resistance\" extinction model posits that Neandertals were disproportionately affected by exposure to novel infectious diseases that were transmitted during the period of spatiotemporal sympatry with modern humans. Comparisons of new archaic hominin paleogenome sequences with modern human genomes have confirmed a history of genetic admixture - and thus direct contact - between humans and Neandertals. Analyses of these data have also shown that Neandertal nuclear genome genetic diversity was likely considerably lower than that of the Eurasian anatomically modern humans with whom they came into contact, perhaps leaving Neandertal innate immune systems relatively more susceptible to novel pathogens. In this study, we compared levels of genetic diversity in genes for which genetic variation is hypothesized to benefit pathogen defense among Neandertals and African, European, and Asian modern humans, using available exome sequencing data (six chromosomes per population). We observed that Neandertals had only 31-39% as many nonsynonymous (amino acid changing) polymorphisms across 73 innate immune system genes compared to modern human populations. We also found that Neandertal genetic diversity was relatively low in an unbiased set of balancing selection candidate genes for primates - genes with the highest 1% genetic diversity genome-wide in non-human apes. In contrast, Neandertals had similar to higher levels of genetic diversity than humans in 13 major histocompatibility complex (MHC) genes. Thus, while Neandertals may have been relatively more susceptible to some novel pathogens and differential pathogen resistance could be considered as one potential contributing factor in their extinction, this model does have limitations.

Evolutionary Biology↗