Biology subjects

Alvarez-Gonzalez, L.

Publications and source records attributed to Alvarez-Gonzalez, L..

4 recordsLinked to original sources

bioRxiv2025

Three-Dimensional Epigenome Roadmap of Human B-cell Differentiation Uncovers Mechanisms of Humoral Immunity and Oncogenesis

Human B-cell differentiation underlies humoral immunity, and its disruption leads to cancer, autoimmunity, and immunodeficiencies. However, the enhancer-based regulatory mechanisms governing this process remain poorly understood. To address this gap, we generated the first three-dimensional epigenomic roadmap of human B-cell differentiation in vivo. By profiling nine differentiation stages, we linked nearly half a million enhancers to their target genes through chromatin interactions, defined their activity states, and predicted bound transcription factors. We show that the acquisition of B-cell identity, distinct from common cellular processes, relies on large enhancer networks acting additively and synergistically to finely tune transcription. We further identify a 3D epigenetic priming mechanism underlying immune memory, whereby memory B cells retain primed DNA loops that enable faster responses to antigen re-exposure. Extending this roadmap to disease, we demonstrate that B-cell malignancies preserve enhancer signatures of their cell of origin while silencing distal tumor suppressor control. Finally, we uncover a previously unappreciated oncogenic mechanism in which intragenic deletions disrupt distal gene regulation via enhancer loss. Together, this resource provides a framework for understanding the genetic and epigenetic basis of humoral immunity and immune-related diseases.

genomics↗

bioRxiv2025

Chromosome-level genomics and historical museum collections reveal new insights into the population structure and chromosome evolution of waterbuck

Advances in the sequencing and assembly of chromosome-level genome assemblies has enabled the study of non-model animals, providing further insights into the evolution of genomes and chromosomes. Here, we present the waterbuck (Kobus ellipsiprymnus) as an emerging model antelope for studying population dynamics and chromosome evolution. Antelope evolutionary history has been shaped by Robertsonian (Rb) fusions, with waterbuck also showing variation in karyotype due to two polymorphic Rb fusions. These polymorphisms are variable between and within the two recognised subspecies, the common and defassa waterbuck. To provide new insights into waterbuck evolution, we firstly assembled a chromosome-level genome assembly for the defassa subspecies using PacBio HiFi and Hi-C sequencing. We then utilised museum collections to carry out whole genome sequencing (WGS) of 24 historical waterbuck skins from both subspecies. Combined with a previous WGS dataset (n = 119), this represents the largest study of waterbuck populations to date. We found novel population structure and gene flow between waterbuck populations and regions across the genome with high genomic differentiation between the two subspecies. Several of these regions were found around the centromeres of fixed and polymorphic Rb fusions, exhibiting signatures of low recombination and local population structure. Interestingly, these regions contain genes involved in development, fertility, and recombination. Our results highlight the importance of assembling genomes to the chromosome-level, the utility and value of historical collections in sampling a wide-ranging species to uncover fine-scale population structure, and the potential impacts of Rb fusions on genomic differentiation and the recombination landscape.

evolutionary biology↗

bioRxiv2024

A punctuated burst of massive genomic rearrangements by chromosome shattering and the origin of non-marine annelids

The genomic basis of cladogenesis and adaptive evolutionary change has intrigued biologists for decades. Here, we show that the tectonics of genome evolution in clitellates, a clade composed of most freshwater and all terrestrial species of the phylum Annelida, is characterised by extensive genome-wide scrambling that resulted in a massive loss of macrosynteny between marine annelids and clitellates. These massive rearrangements included the formation of putative neocentromeres with newly acquired transposable elements and preceded a further period of genome-wide reshaping events, potentially triggered by the loss of genes involved in genome stability and homeostasis of cell division. Notably, while these rearrangements broke short-range interactions observed between Hox genes in marine annelids, they were reformed as long-range interactions in clitellates. Our findings reveal extensive genomic reshaping in clitellates at both the linear (2D) and three-dimensional (3D) levels, suggesting that, unlike in other animal lineages where synteny conservation constrains structural evolution, clitellates exhibit a remarkable tolerance for chromosomal rearrangements. Our study thus suggests that the genomic landscape of Clitellata resulted from a rare burst of genomic changes that ended a long period of stability that persists across large phylogenetic distances.

evolutionary biology↗

bioRxiv2021

Microchromosomes are building blocks of bird, reptile and mammal chromosomes

Microchromosomes, once considered unimportant shreds of the chicken genome, are gene rich elements with a high GC content and few transposable elements. Their origin has been debated for decades. We used cytological and whole genome sequence comparisons, and chromosome conformation capture, to trace their origin and fate in genomes of reptiles, birds and mammals. We find that microchromosomes as well as macrochromosomes are highly conserved across birds, and share synteny with single small chromosomes of the chordate amphioxus, attesting to their origin as elements of an ancient animal genome. Turtles and squamates (snakes and lizards) share different subsets of ancestral microchromosomes, having independently lost microchromosomes by fusion with other microchromosomes or macrochromosomes. Patterns of fusions were quite different in different lineages. Cytological observations show that microchromosomes in all lineages are spatially separated into a central compartment at interphase and during mitosis and meiosis. This reflects higher interaction between microchromosomes than with macrochromosomes, as observed by chromosome conformation capture, and suggests some functional coherence. In highly rearranged genomes fused microchromosomes retain most ancestral characteristics, but these may erode over evolutionary time; surprisingly de novo microchromosomes have rapidly adopted high interaction. Some chromosomes of early branching monotreme mammals align to several bird microchromosomes, suggesting multiple microchromosome fusions in a mammalian ancestor. Subsequently multiple rearrangements fueled the extraordinary karyotypic diversity of therian mammals. Thus microchromosomes, far from being aberrant genetic elements, represent fundamental building blocks of amniote chromosomes, and it is mammals, rather than reptiles, that are atypical. Significance StatementGenomes of birds and reptiles, but not mammals, consist of a few large chromosomes and many tiny microchromosomes. Once considered unimportant shreds of the genome, microchromosomes are gene rich and highly conserved among bird and reptiles, and share homology with one or more of the tiny chromosomes of an invertebrate that diverged from the vertebrate lineage 684 million years ago. Microchromosomes interact strongly and crowd together at the centre of cells, suggesting functional coherence. Many microchromosomes have been lost independently in turtles, snakes and lizards as they have fused with each other, or with larger chromosomes. In mammals they have completely disappeared, yet some chromosomes of the basal platypus line up with several microchromosomes, suggesting that they are the building blocks of the atypically variable chromosomes of mammals.

genomics↗