Biology subjects

Brambilla, A.

Publications and source records attributed to Brambilla, A..

6 recordsLinked to original sources

bioRxiv2026

Fine-tuning m6A and METTL3 levels have profound impact on cellular proliferation and protein synthesis

The RNA modification m6A is the most abundant internal RNA modification in eukaryotic mRNAs and long non-coding RNAs and has been implicated in diverse and important biological processes. Notably, m6A has been associated with both pro and anti-tumorigenic roles depending on cellular and biological context. In basal-like triple negative breast cancer (TNBC), heterozygous loss of the m6A methyltransferase METTL3 and increased levels of the m6A demethylase FTO are associated with poor prognosis and an increased risk of metastasis. Here, using CRISPR generated METTL3 heterozygous knockout TNBC cell lines (MDA-MB-468) and Nanopore direct RNA sequencing, we characterise transcriptome-wide changes in m6A modification patterns following partial loss of METTL3. We reveal that partial loss of global m6A is associated with preferential changes in the methylation status of transcripts involved in translational control, leading to an increase in translational output and proliferative capacity. In contrast, strong pharmacologic inhibition of METTL3 suppresses translation and proliferation. Our findings highlight how m6A levels differentially regulate gene expression in a dose dependent manner and provides a deeper molecular understanding of the RNA modification m6A and its role in fine-tuning translation and affecting both tumorigenesis and cancer progression.

molecular biology↗

bioRxiv2024

A highly contiguous reference genome for the Alpine ibex (Capra ibex)

Species conservation efforts can be threatened by deleterious mutation accumulation following population contractions. In addition to de novo mutations, a significant source of genetic load could be deleterious variants introduced into a population through hybridization. Hence, even successfully restored species may face deleterious mutation swamping due to hybridization with an abundant and closely related species. The outcomes of such hybridization events are poorly understood given the complex interplay of introduced adaptive and maladaptive variation. Here, we analyze this potential risk for Alpine ibex (Capra ibex), a flagship species of large mammal restoration in the Alps. Near-extinction two centuries ago resulted in exceptionally low genome-wide diversity and increased inbreeding, which facilitated the purging of severe deleterious mutations but accumulation of less severe ones. We produced a highly contiguous chromosome-level genome assembly of the Alpine ibex capturing structural divergence from its closest domestic species, the domestic goat (Capra hircus) known to hybridize with Alpine ibex Genome sequencing of eight recent ibex-goat hybrids and backcrosses from two hybrid swarms in Northern Italy revealed highly diverse recombinants and an average of 30 masked, predicted loss-of-function (LOF) mutations per hybrid compared to 10 in non-hybrid Alpine ibex. This exposes Alpine ibex to further backcrosses, exposing their vulnerable gene pool to an influx of hybridization load. Individual-based genomic simulations suggest that such LOF load would return to pre- hybridization levels with a lag of over 100 generations after gene flow subsides. Hybridization could also disrupt local adaptation in the recipient species. Our work provides a direct estimate of hybridization load and, by this, informs on the complexity of managing endangered gene pools in the face of hybridization.

evolutionary biology↗

bioRxiv2023

Genetic evidence of a hybrid swarm between Alpine ibex and domestic goat

Improving the understanding of the causes and effects of anthropogenic hybridization is fundamental to ensure the conservation of wild species, particularly in the case of hybridization between wild species and their domestic relatives. Knowledge is missing for many species also because of a lack of appropriate tools for hybrid identification. Here, coupling genotype and phenotype analysis, we carried out an extensive investigation of ongoing hybridization in Alpine ibex Capra ibex, a mountain ungulate of conservation concern from a genetic perspective. By genotyping at 63 diagnostic and 465 neutral SNPs 20 suspected hybrids and 126 Alpine ibex without suspicious phenotype, representing eight populations across a major part of the species distribution, we found evidence for ongoing hybridization between Alpine ibex and domestic goat. We identified different levels of hybridization including back crosses into both Alpine ibex and domestic goat. Our results suggest a lack of reproductive barriers between the two species and good survival and reproductive success of the hybrids. Hybridization was locally intense, alike a hybrid swarm, but not spread across the rest of the species distribution. Most of the hybrids were discovered in two locations in the North-West of Italy, while random sampling of individuals from different areas did not provide evidence of recent hybridization. Our method, based on Amplicon sequencing of 63 diagnostic SNPs specifically developed for this purpose, allowed us to identify hybrids and back crosses up to the 4th-5th generation and was suitable for genetic samples of different quality, although with varying levels of certainty regarding the exact number of generations passed since hybridization. Based on the paired analysis of genotype and phenotype we provide guidelines for a first identification of hybrids in the field and suggest a procedure for the reliable identification of hybrids.

evolutionary biology↗

bioRxiv2021

Long term analysis of social structure: evidence of age-based consistent associations in Alpine ibex

Despite its recognized importance for understanding the evolution of animal sociality as well as for conservation, long term analysis of social networks of animal populations is still relatively uncommon. We investigated social network dynamics in males of a gregarious mountain ungulate (Alpine ibex, Capra ibex) over ten years focusing on groups, sub-groups and individuals, exploring the dynamics of sociality over different scales. Despite the social structure changing between seasons, the Alpine ibex population was highly cohesive: fission-fusion dynamics lead almost every male in the population to associate with each other male at least once. Nevertheless, we found that male Alpine ibex showed preferential associations that were maintained across seasons and years. Age seemed to be the most important factor driving preferential associations while other characteristics, such as social status, appeared less crucial. We also found that centrality measures were influenced by age and were also related to individual physical condition. The multi-scale and long-term frame of our study helped us show that ecological constrains, such as resource availability, may play a role in shaping associations in a gregarious species, but they cannot solely explain sociality and preferential association that are likely also to be driven by life-history linked physiological and social needs. Our results highlight the importance of long-term studies based on individually recognizable subjects to help us build on our understanding of the evolution of animal sociality.

animal behavior and cognition↗

bioRxiv2020

A robust sequencing assay of a thousand amplicons for the high-throughput population monitoring of Alpine ibex immunogenetics

Genetic variation is a major factor determining susceptibility to diseases. Polymorphism at the major histocompatibility complex (MHC) and other immune function loci can underlie health and reproductive success of individuals. Endangered species of low population size could be severely compromised to evolve disease resistance due to reduced adaptive variation. A major impediment to screen adaptive genetic variation in wild species is the difficulty to comprehensively genotype immune-related loci based on low input material. Here, we design and validate a targeted amplicon sequencing assay to parallelize the analysis of a thousand loci of the MHC, other immunity-related genes, and genome-wide markers for the assessment of population structure. We apply the approach to Alpine ibex, one of the most successful examples of restoration of a large mammal in Europe. We used 51 whole genome sequenced individuals to select representative target SNPs. We integrated SNP call data from four related species for amplification robustness and genotyped 158 Alpine ibex individuals for validation. We show that the genome-wide markers perform equally well at resolving population structure as RAD-seq or low-coverage genome sequencing datasets with orders of magnitude more markers. The targeted amplicon sequencing assay is robust to >100-fold variation in input DNA quantity and generates useful genotype information from fecal samples. The amplicon marker set also identified recent species hybridization events with domestic goats. The immune loci show unexpectedly high degrees of differentiation within the species. Our assay strategy can realistically be implemented into population genetic surveys of a large range of species.

genomics↗

bioRxiv2019

Alkyladenine DNA glycosylase associates with transcription elongation to coordinate DNA repair with gene expression

Base excision repair (BER) initiated by alkyladenine DNA glycosylase (AAG; aka MPG) is essential for removal of aberrantly methylated DNA bases. Genome instability and accumulation of aberrant bases accompany multiple diseases including cancer and neurological disorders. While BER is well studied on naked DNA, it remains unclear how BER efficiently operates on chromatin. Here we show that AAG binds to chromatin and forms complex with active RNA polymerase (pol) II. This occurs through direct interaction with Elongator and results in transcriptional co-regulation. Importantly, at co-regulated genes aberrantly methylated bases accumulate towards 3end, in regions enriched for BER enzymes AAG and APE1, Elongator and active RNA pol II. Active transcription and functional Elongator are further crucial to ensure efficient BER, by promoting AAG and APE1 chromatin recruitment. Our findings provide novel insights to maintaining genome stability in actively transcribing chromatin, and reveal roles of aberrantly methylated bases in regulation of gene expression.

molecular biology↗