Recovering the genomes hidden in museum wet collections

Natural history museums hold vast collections of biomaterials. The collections in museums, often painstakingly sampled, are largely unexplored treasures that may help us better understand biodiversity on the planet. Museum collections can provide a unique window into the past of species long gone or currently declining due to human activity. From a molecular perspective, however, many museum samples are stored under conditions that hasten the damage of DNA, RNA and proteins. For example, samples in wet collections are those stored in liquid preservatives, typically ethanol. These ethanol-preserved tissues are often, although not always, formalin-fixed prior to storage, which may damage DNA. In this and recent issues of Molecular Ecology Resources, Straube et al (2021), O'Connell et al (2021) and Hahn et al (2022) explore different types of specimens from museum wet collections as new sources of DNA for scientific studies. All three articles found that for wet museum collections, overall specimen condition mattered most for recovering high-quality genomic DNA

Characterization of nuclear mitochondrial insertions in the whole genomes of primates

Altres ajuts: CERCA Programme/Generalitat de Catalunya i Obra Social "La Caixa"The transfer and integration of whole and partial mitochondrial genomes into the nuclear genomes of eukaryotes is an ongoing process that has facilitated the transfer of genes and contributed to the evolution of various cellular pathways. Many previous studies have explored the impact of these insertions, referred to as NumtS, but have focused primarily on older events that have become fixed and are therefore present in all individual genomes for a given species. We previously developed an approach to identify novel Numt polymorphisms from next-generation sequence data and applied it to thousands of human genomes. Here, we extend this analysis to 79 individuals of other great ape species including chimpanzee, bonobo, gorilla, orang-utan and also an old world monkey, macaque. We show that recent Numt insertions are prevalent in each species though at different apparent rates, with chimpanzees exhibiting a significant increase in both polymorphic and fixed Numt sequences as compared to other great apes. We further assessed positional effects in each species in terms of evolutionary time and rate of insertion and identified putative hotspots on chromosome 5 for Numt integration, providing insight into both recent polymorphic and older fixed reference NumtS in great apes in comparison to human events

Genetic variation in pan species is shaped by demographic history and harbors lineage-specific functions

Chimpanzees (Pan troglodytes) and bonobos (Pan paniscus) are the closest living relatives of humans, but the two species show distinct behavioral and physiological differences, particularly regarding female reproduction. Despite their recent rapid decline, the demographic histories of the two species have been different during the past 1-2 Myr, likely having an impact on their genomic diversity. Here, we analyze the inferred functional consequences of genetic variation across 69 individuals,making use of themost complete data set of genomes in the Pan clade to date.We test towhich extent the demographic history influences the efficacy of purifying selection in these species.We find that small historical effective population sizes (Ne) correlate not only with low levels of genetic diversity but also with a larger number of deleterious alleles in homozygosity and an increased proportion of deleterious changes at lowfrequencies. Toinvestigate the putativegeneticbasis forphenotypic differencesbetweenchimpanzees andbonobos, we exploit the catalog of putatively deleterious protein-coding changes in each lineage.We show that bonobo-specific nonsynonymous changes are enrichedin genes relatedtoage atmenarche inhumans, suggesting that the prominent physiologicaldifferences in the female reproductive systembetweenchimpanzees andbonobosmightbe explained, inpart,byputatively adaptive changeson the bonobo lineage

Genomics reveals introgression and purging of deleterious mutations in the Arabian leopard (Panthera pardus nimr)

In endangered species, low-genetic variation and inbreeding result from recent population declines. Genetic screenings in endangered populations help to assess their vulnerability to extinction and to create informed management actions toward their conservation efforts. The leopard, Panthera pardus, is a highly generalist predator with currently eight different subspecies. Yet, genomic data are still lacking for the Critically Endangered Arabian leopard (P. p. nimr). Here, we sequenced the whole genome of two Arabian leopards and assembled the most complete genomic dataset for leopards to date. Our phylogenomic analyses show that leopards are divided into two deeply divergent clades: the African and the Asian. Conservation genomic analyses indicate a prolonged population decline, which has led to an increase in inbreeding and runs of homozygosity, with consequent purging of deleterious mutations in both Arabian individuals. Our study represents the first attempt to genetically inform captive breeding programmes for this Critically Endangered subspecies

Functional Implications of Human-Specific Changes in Great Ape microRNAs

microRNAs are crucial post-transcriptional regulators of gene expression involved in a wide range of biological processes. Although microRNAs are highly conserved among species, the functional implications of existing lineage-specific changes and their role in determining differences between humans and other great apes have not been specifically addressed. We analyzed the recent evolutionary history of 1,595 human microRNAs by looking at their intra-and inter-species variation in great apes using high-coverage sequenced genomes of 82 individuals including gorillas, orangutans, bonobos, chimpanzees and humans. We explored the strength of purifying selection among microRNA regions and found that the seed and mature regions are under similar and stronger constraint than the precursor region. We further constructed a comprehensive catalogue of microRNA species-specific nucleotide substitutions among great apes and, for the first time, investigated the biological relevance that human-specific changes in microRNAs may have had in great ape evolution. Expression and functional analyses of four microRNAs (miR-299-3p, miR-503-3p, miR508-3p and miR-541-3p) revealed that lineage-specific nucleotide substitutions and changes in the length of these microRNAs alter their expression as well as the repertoires of target genes and regulatory networks. We suggest that the studied molecular changes could have modified crucial microRNA functions shaping phenotypes that, ultimately, became human-specific. Our work provides a frame to study the impact that regulatory changes may have in the recent evolution of our species.Peer reviewe

A genomic exploration of the early evolution of extant cats and their sabre-toothed relatives

Background: The evolutionary relationships of Felidae during their Early-Middle Miocene radiation is contentious. Although the early common ancestors have been subsumed under the grade-group Pseudaelurus, this group is thought to be paraphyletic, including the early ancestors of both modern cats and extinct sabretooths. Methods: Here, we sequenced a draft nuclear genome of Smilodon populator, dated to 13,182 ± 90 cal BP, making this the oldest palaeogenome from South America to date, a region known to be problematic for ancient DNA preservation. We analysed this genome, together with genomes from other extinct and extant cats to investigate their phylogenetic relationships. Results: We confirm a deep divergence (~20.65 Ma) within sabre-toothed cats. Through the analysis of both simulated and empirical data, we show a lack of gene flow between Smilodon and contemporary Felidae. Conclusions: Given that some species traditionally assigned to Pseudaelurus originated in the Early Miocene ~20 Ma, this indicates that some species of Pseudaelurus may be younger than the lineages they purportedly gave rise to, further supporting the hypothesis that Pseudaelurus was paraphyletic

Genomes reveal marked differences in the adaptive evolution between orangutan species

Integrating demography and adaptive evolution is pivotal to understanding the evolutionary history and conservation of great apes. However, little is known about the adaptive evolution of our closest relatives, in particular if and to what extent adaptions to environmental differences have occurred. Here, we used whole-genome sequencing data from critically endangered orangutans from North Sumatra (Pongo abelii) and Borneo (P. pygmaeus) to investigate adaptive responses of each species to environmental differences during the Pleistocene

Transcriptome innovations in primates revealed by single-molecule long-read sequencing

Transcriptomic diversity greatly contributes to the fundamentals of disease, lineage-specific biology, and environmental adaptation. However, much of the actual isoform repertoire contributing to shaping primate evolution remains unknown. Here, we combined deep long- and short-read sequencing complemented with mass spectrometry proteomics in a panel of lymphoblastoid cell lines (LCLs) from human, three other great apes, and rhesus macaque, producing the largest full-length isoform catalog in primates to date. Around half of the captured isoforms are not annotated in their reference genomes, significantly expanding the gene models in primates. Furthermore, our comparative analyses unveil hundreds of transcriptomic innovations and isoform usage changes related to immune function and immunological disorders. The confluence of these evolutionary innovations with signals of positive selection and their limited impact in the proteome points to changes in alternative splicing in genes involved in immune response as an important target of recent regulatory divergence in primates