Biology subjects

Iniguez, L. P.

Publications and source records attributed to Iniguez, L. P..

9 recordsLinked to original sources

bioRxiv2026

Alternative splicing and gene expression repurpose ancestral genes through distinct evolutionary routes

Specialized tissues often evolve by repurposing ancestral genes. Tissue-specific alternative splicing (TS-AS) and tissue-specific gene expression (TS-GE) have been proposed as complementary mechanisms contributing to tissue specialization, but whether they provide broadly interchangeable solutions or instead follow distinct, constrained evolutionary routes remains unknown. To address this question, here we compare TS-AS and TS-GE across eight homologous tissues, 20 bilaterian species and 7,178 ancestral gene families spanning 700 million years. The two mechanisms were similarly prevalent and, together, they affected nearly three-quarters of ancestral gene families across our dataset. However, they targeted largely non-overlapping gene sets within species, with contrasting architectures and functions. TS-AS usually acts on longer, exon-rich genes and modulates intracellular machinery shared across tissues, whereas TS-GE preferentially evolves in duplicated genes and impacts tissue-defining extracellular and nuclear processes. Unexpectedly, although TS-GE was globally more conserved, neural-specific splicing gains outnumbered expression gains at the origins of vertebrates and insects, revealing a prominent contribution of TS-AS to early nervous system transcriptome diversification. Exon-level orthology reconstructions further uncovered extensive recurrent evolution of neural-specific exons in the same ancestral genes across the phylogeny. Importantly, deletion of two such microexons in Drosophila negatively impacted overall fitness and led to neurological-associated phenotypes such as reduced climbing or hyperactivity. Altogether, our findings reveal distinct but complementary evolutionary routes by which gene expression and alternative splicing repurpose ancestral genes, and highlight recurrent neural exon evolution as a functionally important contributor to nervous systems.

evolutionary biology↗

bioRxiv2026

Evolutionary landscapes of zygotic genome activation across animals

During early animal embryogenesis, gene expression control shifts from maternally deposited products to newly transcribed RNA through zygotic genome activation (ZGA). Although essential and universal, ZGA remains poorly understood outside a few model species. Here, we generated a transcriptomic atlas of early embryogenesis across 61 animal species from 13 phyla and used a unified computational framework to infer ZGA timing systematically. We find extensive variation in ZGA onset across animals, but show that the ratio between genome size and egg cytoplasmic volume, a proxy for the nuclear-to-cytoplasmic ratio, robustly predicts when genome activation begins. We also reveal that zygotic genes also differ from maternal transcripts in genomic architecture, function and evolutionary conservation, suggesting that ZGA follows a conserved molecular logic despite flexible transcriptomic outputs.

evolutionary biology↗

bioRxiv2025

Neural microexons modulate arousal states via cAMP signalling in zebrafish

Arousal states, often dysregulated in neurodevelopmental disorders, shape how organisms perceive and respond to their environment. Here, we show that srrm3, a master regulator of neural microexons, is essential for normal arousal in zebrafish larvae. srrm3 mutants exhibit persistent hyperarousal, including sleep loss, sensory hypersensitivity, anxiety-like behaviour, and heightened neural and behavioural activity. Elevated cAMP signalling likely drives this hyperarousal, as pharmacologically reducing cAMP rescues mutant behaviour, while increasing cAMP in wild-type larvae phenocopies the mutant hyperaroused state. Pharmacological cAMP modulation also mimics and reverses srrm3-dependent transcriptional changes. These include immediate early gene downregulation, which, together with altered activity-dependent transcription factor motif occupancy, suggest adaptation to sustained neuronal hyperactivity. Additionally, srrm3 mutants show upregulation of microexon- containing genes, likely compensating for microexon loss. Together, these findings reveal a role for neural microexons in shaping arousal via cAMP signalling, providing insight into how splicing defects may underlie sensory and sleep disturbances.

neuroscience↗

bioRxiv2024

Phenotypic impact of individual conserved neuronal microexons and their master regulators in zebrafish

Microexons exhibit striking evolutionary conservation and are subject to precise, switch-like regulation in neurons, orchestrated by the splicing factors Srrm3 and Srrm4. Disruption of these regulators in mice leads to severe neurological phenotypes, and their misregulation is linked to human disease. However, the specific microexons involved in these phenotypes and the effects of individual microexon deletions on neurodevelopment, physiology, and behavior remain poorly understood. To explore this, we generated zebrafish lines with deletions of 18 individual microexons, alongside srrm3 and srrm4 mutant lines, and conducted comprehensive phenotypic analyses. We discovered that while loss of srrm3, alone or together with srrm4, resulted in significant alterations in neuritogenesis, locomotion, and social behavior, individual microexon deletions typically produced mild or no noticeable effects. Nonetheless, we identified specific microexons associated with defects in neuritogenesis (evi5b, vav2, itsn1, src) and social behavior (vti1a, kif1b). Additionally, most microexon deletions triggered coordinated transcriptomic changes in neural pathways, suggesting the presence of molecular compensatory mechanisms. Our findings suggest that the severe phenotypes caused by Srrm3/4 depletion arise from the combined effects of multiple subtle disruptions across various cellular pathways, which are individually well-tolerated.

molecular biology↗

bioRxiv2023

A single-cell transposable element atlas of human cell identity

Single cell RNA sequencing (scRNA-seq) is revolutionizing the study of complex biological systems. However, most sequencing studies overlook the contribution of transposable element (TE) expression to the transcriptome. In both scRNA-seq and bulk tissue RNA sequencing (RNA-seq), quantification of TE expression is challenging due to repetitive sequence content and poorly characterized TE gene models. Here, we developed a tool and analysis pipeline for Single cell Transposable Element Locus Level Analysis of scRNA Sequencing (Stellarscope) that reassigns multi-mapped reads to specific genomic loci using an expectation-maximization algorithm. Using Stellarscope, we built an atlas of TE expression in human PBMCs. We found that locus-specific TEs delineate cell types and define new cell subsets not identified by standard mRNA expression profiles. Altogether, this study provides comprehensive insights into the influence of transposable elements in human biology.

genomics↗

bioRxiv2023

Transposable elements may enhance antiviral resistance in HIV-1 elite controllers

Less than 0.5% of people living with HIV-1 are elite controllers (ECs) - individuals who have a replication-competent viral reservoir in their CD4+ T cells but maintain undetectable plasma viremia without the help of antiretroviral therapy. While the EC CD4+ T cell transcriptome has been investigated for gene expression signatures associated with disease progression (or, in this case, a lack thereof), the expression and regulatory activity of transposable elements (TEs) in ECs has not been explored. Yet previous studies have established that TEs can directly impact the immune response to pathogens, including HIV-1. Thus, we hypothesize that the regulatory activities of TEs could contribute to the natural resistance of ECs against HIV-1. We perform a TE-centric analysis of previously published multi-omics data derived from EC individuals and other populations. We find that the CD4+ T cell transcriptome and retrotranscriptome of ECs are distinct from healthy controls, treated patients, and viremic progressors. However, there is a substantial level of transcriptomic heterogeneity among ECs. We categorize individuals with distinct chromatin accessibility and expression profiles into four clusters within the EC group, each possessing unique repertoires of TEs and antiviral factors. Notably, several TE families with known immuno-regulatory activity are differentially expressed among ECs. Their transcript levels in ECs positively correlate with their chromatin accessibility and negatively correlate with the expression of their KRAB zinc-finger (KZNF) repressors. This coordinated variation is seen at the level of individual TE loci likely acting or, in some cases, known to act as cis-regulatory elements for nearby genes involved in the immune response and HIV-1 restriction. Based on these results, we propose that the EC phenotype is driven in part by the reduced availability of specific KZNF proteins to repress TE-derived cis-regulatory elements for antiviral genes, thereby heightening their basal level of resistance to HIV-1 infection. Our study reveals considerable heterogeneity in the CD4+ T cell transcriptome of ECs, including variable expression of TEs and their KZNF controllers, that must be taken into consideration to decipher the mechanisms enabling HIV-1 control.

immunology↗

bioRxiv2022

Pervasive evolution of tissue-specificity of ancestral genes differentially shaped vertebrates and insects

Regulation of gene expression is arguably the main mechanism contributing to tissue phenotypic diversity within and between species. Here, we assembled an extensive transcriptomic dataset covering twenty bilaterian species and eight tissues, selecting a specular phylogeny that allowed both the combined and parallel investigation of gene expression evolution between vertebrates and insects. We specifically focused on widely conserved ancestral genes, identifying strong cores of pan-bilaterian tissue-specific genes and even larger groups that diverged to define vertebrate and insect tissues. Systematic inferences of tissue-specificity gains and losses show that nearly half of all ancestral genes have been recruited into tissue-specific transcriptomes. This occurred during both ancient and, especially, recent bilaterian evolution, with several gains being associated with the emergence of unique phenotypes. Such pervasive evolution of tissue-specificity was linked to gene duplication coupled with specialization, including an unappreciated prolonged effect of whole genome duplications during recent vertebrate evolution.

genomics↗

bioRxiv2022

Control of pancreatic islet function and glucose homeostasis by a novel microexon program misregulated in type 2 diabetes

Pancreatic islets control glucose homeostasis by the balanced secretion of insulin and other hormones, and their abnormal function causes diabetes or hypoglycemia. Here, we uncover a conserved program of alternative microexons included in mRNAs of islet cells, particularly in genes involved in vesicle transport and exocytosis. Islet microexons (IsletMICs) are regulated by the RNA binding protein SRRM3 and represent a subset of the larger neural program that are particularly sensitive to the levels of this regulator. Both SRRM3 and IsletMICs are induced by elevated glucose levels, and depletion of SRRM3 in beta cell lines and mouse islets, or repression of particular IsletMICs using antisense oligonucleotides, leads to inappropriate insulin secretion. Consistently, SRRM3 mutant mice display defects in islet cell identity and function, leading to hyperinsulinemic hypoglycemia. Importantly, human genetic variants that influence SRRM3 expression and IsletMIC inclusion in islets are associated with fasting glucose variation and type 2 diabetes risk.

molecular biology↗

bioRxiv2018

Telescope: Characterization of the retrotranscriptome by accurate estimation of transposable element expression

Characterization of Human Endogenous Retrovirus (HERV) expression within the transcriptomic landscape using RNA-seq is complicated by uncertainty in fragment assignment because of sequence similarity. We present Telescope, a computational software tool that provides accurate estimation of transposable element expression (retrotranscriptome) resolved to specific genomic locations. Telescope directly addresses uncertainty in fragment assignment by reassigning ambiguously mapped fragments to the most probable source transcript as determined within a Bayesian statistical model. We demonstrate the utility of our approach through single locus analysis of HERV expression in 13 ENCODE cell types. When examined at this resolution, we find that the magnitude and breadth of the retrotranscriptome can be vastly different among cell types. Furthermore, our approach is robust to differences in sequencing technology, and demonstrates that the retrotranscriptome has potential to be used for cell type identification. Telescope performs highly accurate quantification of the retrotranscriptomic landscape in RNA-seq experiments, revealing a differential complexity in the transposable element biology of complex systems not previously observed. Telescope is available at github.com/mlbendall/telescope.\n\nAuthor SummaryAlmost half of the human genome is composed of Transposable elements (TEs), but their contribution to the transcriptome, their cell-type specific expression patterns, and their role in disease remains poorly understood. Recent studies have found many elements to be actively expressed and involved in key cellular processes. For example, human endogenous retroviruses (HERVs) are reported to be involved in human embryonic stem cell differentiation. Discovering which exact HERVs are differentially expressed in RNA-seq data would be a major advance in understanding such processes. However, because HERVs have a high level of sequence similarity it is hard to identify which exact HERV is differentially expressed. To solve this problem, we developed a computer program which addressed uncertainty in fragment assignment by reassigning ambiguously mapped fragments to the most probable source transcript as determined within a Bayesian statistical model. We call this program, \"Telescope\". We then used Telescope to identify HERV expression in 13 well-studied cell types from the ENCODE consortium and found that different cell types could be characterized by enrichment for different HERV families, and for locus specific expression. We also showed that Telescope performed better than other methods currently used to determine TE expression. The use of this computational tool to examine new and existing RNA-seq data sets may lead to new understanding of the roles of TEs in health and disease.

genomics↗