Estructura del genoma

El genoma és una estructura altament dinàmica amb una certa tendència a la inestabilitat, i està, per tant, subjecte a l'escrutini de la selecció natural. En el camí d'entendre el genoma hem pogut observar el paper clau que tenen les repeticions (de tota mena) per comprendre l'evolució estructural del genoma humà i com es relaciona l'estructura i la funció. Així, recentment, hem pogut apreciar que, a part de les variacions clàssiques i els SNP (polimorfismes d'un sol nucleòtid), els mamífers (com a mínim els ratolins i els humans) tenim una estructura dels nostres genomes altament variable. L'estudi de les regions variants en nombre de còpia (structural variants o copy number polymorphism) ens ha permès observar que els canvis en l'estructura tenen repercussió en l'expressió dels gens, que es tradueixen tant en variabilitat fenotípica entre individus com, en casos més extrems, en malalties. En aquest capítol donarem una visió sobre l'estructura i el dinamisme del genoma, centrantnos en aspectes evolutius del polimorfisme humà i la malaltia.Every mammalian genome is an unstable and highly dynamic structure and therefore subjected to the strict evaluation of natural selection. In the last decades, we have changed our vocabulary and we have been using genomics instead of genetics, mainly because of the revolution on our research techniques. In the way of the understanding of the genomes, we realized how important repeats are and their role in the evolution of the structure of the human genome and how this structure and different functions are related. We have seen for instance that besides of the variation caused for SNPs (Single Nucleotide Polymorphism), the mammals (and specifically humans) are highly structural variant. The study of SVs (Structural Variant regions) and CNPs (Copy Number Polymorphisms) has allowed us to see that changes in structure have important consequences, from genomic diseases to simply affecting genes and its expression and hence, being responsible of the huge phenotypical variability observed among individuals. In this chapter, we will give our view on the structure and dynamism of the genome, from an evolutionary point of view, covering human polymorphism and diseases

Molecular dating of caprines using ancient DNA sequences of Myotragus balearicus, an extinct endemic Balearic mammal

Background: Myotragus balearicus was an endemic bovid from the Balearic Islands (Western Mediterranean) that became extinct around 6,000-4,000 years ago. The Myotragus evolutionary lineage became isolated in the islands most probably at the end of the Messinian crisis, when the desiccation of the Mediterranean ended, in a geological date established at 5.35 Mya. Thus, the sequences of Myotragus could be very valuable for calibrating the mammalian mitochondrial DNA clock and, in particular, the tree of the Caprinae subfamily, to which Myotragus belongs. Results: We have retrieved the complete mitochondrial cytochrome b gene (1,143 base pairs), plus fragments of the mitochondrial 12S gene and the nuclear 28S rDNA multi-copy gene from a well preserved Myotragus subfossil bone. The best resolved phylogenetic trees, obtained with the cytochrome b gene, placed Myotragus in a position basal to the Ovis group. Using the calibration provided by the isolation of Balearic Islands, we calculated that the initial radiation of caprines can be dated at 6.2 ± 0.4 Mya. In addition, alpine and southern chamois, considered until recently the same species, split around 1.6 ± 0.3 Mya, indicating that the two chamois species have been separated much longer than previously thought. Conclusion: Since there are almost no extant endemic mammals in Mediterranean islands, the sequence of the extinct Balearic endemic Myotragus has been crucial for allowing us to use the Messinian crisis calibration point for dating the caprines phylogenetic tree

Genetic diagnosis of autoinflammatory disease patients using clinical exome sequencing

Autoinflammatory diseases comprise a wide range of syndromes caused by dysregulation of the innate immune response. They are difficult to diagnose due to their phenotypic heterogeneity and variable expressivity. Thus, the genetic origin of the disease remains undetermined for an important proportion of patients. We aim to identify causal genetic variants in patients with suspected autoinflammatory disease and to test the advantages and limitations of the clinical exome gene panels for molecular diagnosis. Twenty-two unrelated patients with clinical features of autoinflammatory diseases were analyzed using clinical exome sequencing (~4800 genes), followed by bioinformatic analyses to detect likely pathogenic variants. By integrating genetic and clinical information, we found a likely causative heterozygous genetic variant in NFKBIA (p.D31N) in a North-African patient with a clinical picture resembling the deficiency of interleukin-1 receptor antagonist, and a heterozygous variant in DNASE2 (p.G322D) in a Spanish patient with a suspected lupus-like monogenic disorder. We also found variants likely to increase the susceptibility to autoinflammatory diseases in three additional Spanish patients: one with an initial diagnosis of juvenile idiopathic arthritis who carries two heterozygous UNC13D variants (p.R727Q and p.A59T), and two with early-onset inflammatory bowel disease harbouring NOD2 variants (p.L221R and p.A728V respectively). Our results show a similar proportion of molecular diagnosis to other studies using whole exome or targeted resequencing in primary immunodeficiencies. Thus, despite its main limitation of not including all candidate genes, clinical exome targeted sequencing can be an appropriate approach to detect likely causative variants in autoinflammatory diseases

A new assemblage of late Neanderthal remains from Cova Simanya (NE Iberia)

This study presents an exceptional collection of 54 Late Pleistocene human remains that correspond to at least three Neanderthal individuals from Simanya Gran, the main gallery of Cova Simanya, located in the northeastern Iberian Peninsula. The collection comprised 53 unpublished remains that were unearthed during the 1970s and an additional tooth discovered during 2021 excavations. The specimens represent an adult with a small stature, a periadolescent aged approximately 11.5 years, and an immature individual aged approximately 7.7 years, thus offering a more complete demographic perspective. The collection encompasses diverse anatomical parts including upper and lower dentition, mandible, vertebrae, and limb bones from both the upper and lower extremities. Attempts to extract aDNA were unsuccessful. Renewed archaeological investigations at Cova Simanya have facilitated the reevaluation of the original stratigraphic context of these remains, leading to the discovery of the additional tooth, aligning with the periadolescent individual. This assemblage is currently the most extensive Neanderthal collection from the northeastern Mediterranean Iberia, offering invaluable insights into the morphology and evolutionary trajectory of Late Pleistocene hominins. Hence, Simanya Neanderthals will enhance our understanding of Neanderthal demographics and evolution, paving the way for an in-depth examination of the morphological diversity and evolutionary context of Iberian Neanderthals

Human Oocyte-derived Methylation Differences Persist In The Placenta Revealing Widespread Transient Imprinting

Thousands of regions in gametes have opposing methylation profiles that are largely resolved during the post-fertilization epigenetic reprogramming. However some specific sequences associated with imprinted loci survive this demethylation process. Here we present the data describing the fate of germline-derived methylation in humans. With the exception of a few known paternally methylated germline differentially methylated regions (DMRs) associated with known imprinted domains, we demonstrate that sperm-derived methylation is reprogrammed by the blastocyst stage of development. In contrast a large number of oocyte-derived methylation differences survive to the blastocyst stage and uniquely persist as transiently methylated DMRs only in the placenta. Furthermore, we demonstrate that this phenomenon is exclusive to primates, since no placenta-specific maternal methylation was observed in mouse. Utilizing single cell RNA-seq datasets from human preimplantation embryos we show that following embryonic genome activation the maternally methylated transient DMRs can orchestrate imprinted expression. However despite showing widespread imprinted expression of genes in placenta, allele-specific transcriptional profiling revealed that not all placenta-specific DMRs coordinate imprinted expression and that this maternal methylation may be absent in a minority of samples, suggestive of polymorphic imprinted methylation

A new assemblage of late Neanderthal remains from Cova Simanya (NE Iberia)

This study presents an exceptional collection of 54 Late Pleistocene human remains that correspond to at least three Neanderthal individuals from Simanya Gran, the main gallery of Cova Simanya, located in the northeastern Iberian Peninsula. The collection comprised 53 unpublished remains that were unearthed during the 1970s and an additional tooth discovered during 2021 excavations. The specimens represent an adult with a small stature, a periadolescent aged approximately 11.5 years, and an immature individual aged approximately 7.7 years, thus offering a more complete demographic perspective. The collection encompasses diverse anatomical parts including upper and lower dentition, mandible, vertebrae, and limb bones from both the upper and lower extremities. Attempts to extract aDNA were unsuccessful. Renewed archaeological investigations at Cova Simanya have facilitated the reevaluation of the original stratigraphic context of these remains, leading to the discovery of the additional tooth, aligning with the periadolescent individual. This assemblage is currently the most extensive Neanderthal collection from the northeastern Mediterranean Iberia, offering invaluable insights into the morphology and evolutionary trajectory of Late Pleistocene hominins. Hence, Simanya Neanderthals will enhance our understanding of Neanderthal demographics and evolution, paving the way for an in-depth examination of the morphological diversity and evolutionary context of Iberian Neanderthals.This research was funded by the Spanish Ministry of Science and Innovation through the projects PID2021-122356NB-I00 (MNCN-CSIC, AR), PID2020-113960GB-I00 (UB, JF), PID2021-124590NB-I00 (MCNB, CL-F), PID2019-103987GB-C31 (IPHES-CERCA), and PID2021-126004NB-100 (IBE-UPF-CSIC, TM-B); the AGAUR through the research groups 2021 SGR 01237 (IPHES-CERCA, EA), 2021 SGR 00337 (UB, JF), and 2021 SGR 00177 (IBE-UPF-CSIC, TM-B); the Culture Department of the Generalitat de Catalunya through the project ARQ001SOL-172-2022; and the Diputació de Barcelona and the Fundación Palarq. MS was funded by the UAM Tomás y Valiente Program, JR by the European Union-Next Generation EU, Ministry of Universities and UA (MARSALAS21-22), and DL by the Xunta de Galicia Grant ED481B-2022-048. ST and TM-B received funding from the European Research Council under the European Union’s Horizon 2020 Research and Innovation Program (grant agreement no. 803147 RESOLUTION, https://site.unibo.it/resolution-erc/en (ST), and no. 864203 (TM-B)]. IPHES-CERCA received financial support from the Spanish Ministry of Science and Innovation through the “María de Maeztu” program for Units of Excellence (CEX 2019-000945-M)

A Common Genetic Origin for Early Farmers from Mediterranean Cardial and Central European LBK Cultures

The spread of farming out of the Balkans and into the rest of Europe followed two distinct routes: An initial expansión represented by the Impressa and Cardial traditions, which followed the Northern Mediterranean coastline; and another expansion represented by the LBK (Linearbandkeramik) tradition, which followed the Danube River into Central Europe. Although genomic data now exist from samples representing the second migration, such data have yet to be successfully generated from the initial Mediterranean migration. To address this, we generated the complete genome of a 7,400-yearold Cardial individual (CB13) from Cova Bonica in Vallirana (Barcelona), as well as partial nuclear data from five others excavated from different sites in Spain and Portugal. CB13 clusters with all previously sequenced early European farmers and modern-day Sardinians. Furthermore, our analyses suggest that both Cardial and LBK peoples derived from a common ancient population located in or around the Balkan Peninsula. The Iberian Cardial genome also carries a discernible huntergatherer genetic signature that likely was not acquired by admixture with local Iberian foragers. Our results indicate that retrieving ancient genomes from similarly warm Mediterranean environments such as the Near East is technically feasible

The era of reference genomes in conservation genomics

Progress in genome sequencing now enables the large-scale generation of reference genomes. Various international initiatives aim to generate reference genomes representing global biodiversity. These genomes provide unique insights into genomic diversity and architecture, thereby enabling comprehensive analyses of population and functional genomics, and are expected to revolutionize conservation genomics

Giant tortoise genomes provide insights into longevity and age-related disease

© 2018, The Author(s), under exclusive licence to Springer Nature Limited. Giant tortoises are among the longest-lived vertebrate animals and, as such, provide an excellent model to study traits like longevity and age-related diseases. However, genomic and molecular evolutionary information on giant tortoises is scarce. Here, we describe a global analysis of the genomes of Lonesome George—the iconic last member of Chelonoidis abingdonii—and the Aldabra giant tortoise (Aldabrachelys gigantea). Comparison of these genomes with those of related species, using both unsupervised and supervised analyses, led us to detect lineage-specific variants affecting DNA repair genes, inflammatory mediators and genes related to cancer development. Our study also hints at specific evolutionary strategies linked to increased lifespan, and expands our understanding of the genomic determinants of ageing. These new genome sequences also provide important resources to help the efforts for restoration of giant tortoise populations

On the association between chromosomal rearragements and genic evolution in mammals

The main objectives of this work are:a) To test the predictions of suppressed-recombination chromosomal speciation models on two different lineages of mammals: rodents and rimates. Suppressed-recombination chromosomal speciation is still quite elusive as a mode of speciation in mammals. Experimental results are scarce and the first objective of this work is to analyze whole-genome data looking for traces of events of chromosomal speciation. Rodent and primate lineages were chosen for this search, not just because of their particular biological and cytological characteristics, which make them good candidates to have speciated by this mechanism, but also because they were the first mammalian organisms to be fully sequenced. b) To study the effects of chromosomal rearrangements on genic evolutionary rates. As have been seen in the introduction, there are many of potential interactions among chromosomal rearrangements and evolutionary rates, so the second goal of this work was to try to understand the impact of chromosomal rearrangements over substitution rates by means of other mechanisms not related with speciation. c) To distinguish individual contributions of different genomic factors in the potential association among chromosomal rearrangements and evolutionary rates.The third main goal of this thesis was to discern among the different factors that could be explaining the many associations between chromosomal and genic evolution that were detected in different studies