Biology subjects

Galhardo, M.

Publications and source records attributed to Galhardo, M..

5 recordsLinked to original sources

bioRxiv2026

A dual-phase enhancer couples progenitor maintenance and pancreatic lineage stability

Enhancers orchestrate transcriptional programs that control organ development and maintain differentiated cell states, yet how individual enhancers integrate developmental and long-term tissue maintenance logic remains poorly understood. Here, we identify a distal enhancer downstream of ptf1a (z3-DpE) as a regulatory node coupling pancreatic development with acinar cell homeostasis in zebrafish. Deletion of z3-DpE reduces ptf1a expression in pancreatic multipotent progenitor cells (MPCs), leading to depletion of the progenitor pool, altered morphogenesis, and premature exocrine differentiation. Transcriptomic analysis reveals broad repression of proliferation- and morphogenesis-related genes, including Notch pathway components essential for progenitor maintenance. After differentiation, loss of z3-DpE contributes to acinar cell loss, expansion of ductal and endocrine compartments, and disrupted pancreatic architecture. Chromatin-accessibility profiling of purified acinar cells reveals that reduced ptf1a activity leads to widespread remodeling of the acinar chromatin landscape, with decreased accessibility at loci associated with acinar identity and developmental programs, and increased accessibility at sites linked to inflammation, epithelial plasticity, and pancreatic cancer susceptibility. Histopathological analysis shows disorganized acinar tissue with increased duct-like structures and mucinous lesions reminiscent of early pancreatic neoplasia. Thus, z3-DpE safeguards acinar identity by sustaining ptf1a expression and a chromatin landscape that restricts fate instability and pathological plasticity. Our findings demonstrate the mechanistic sufficiency of a single enhancer to coordinate progenitor expansion and long-term lineage stabilization, providing a paradigm for how a developmental regulatory element is redeployed to preserve tissue integrity and suppress disease-associated plasticity.

developmental biology↗

bioRxiv2025

The Insertion of an ATTTC Repeat in an Alu Element Hyperactivates a Primate-Specific Neurodevelopmental Enhancer in Spinocerebellar Ataxia Type 37

Alu are evolutionarily very old primate-specific interspersed repeat elements that constitute [~]11% of the human genome. They are a source of short tandem repeats (STRs), which often expand in size and originate inherited neuromuscular and neurodegenerative disorders. How expanded STR insertion mutations within Alu STRs culminate in disease remains unknown. Here we report an Alu STR located in an intron of DAB1 that functions as a neurodevelopmental enhancer. We demonstrated that an ATTTC repeat insertion in this DAB1 Alu STR, known to cause spinocerebellar ataxia type 37 (SCA37), hyperactivates a neurodevelopmental DAB1 enhancer. Importantly, we showed that neurons derived from SCA37 subjects have higher levels of DAB1 expression and DAB1 overexpression causes abnormal axonal pathfinding in vivo. Overall, these results establish that neuronal dysregulation of a developmental DAB1 Alu STR enhancer contributes to SCA37 pathogenesis, an unexplored mechanism likely acting in many Alu STR diseases, potentially reshaping the therapeutic landscape.

genetics↗

bioRxiv2025

Chemical enhancement of DNA repair in aging

DNA damage is a central driver of the aging process. We previously found that KIF2C, known to play a role in DNA repair, is repressed in aged cells. Here, we investigated if increased KIF2C activity counteracts DNA damage and its effects on aging phenotypes. We show that a small-molecule agonist of KIF2C enhances DNA repair in two distinct genetic disorders exhibiting DNA damage and accelerated aging, the Hutchinson-Gilford progeria (HGPS) and Down (DS) syndromes. Mechanistically, the KIF2C agonist improves the repair of DNA double-strand breaks by inducing nuclear envelope invaginations poked by cytoplasmic microtubules, which translated into amended epigenetic and transcriptional signatures of HGPS and DS. Moreover, subcutaneous administration of the KIF2C agonist in progeria mice mitigated aging phenotypes, extending their healthspan. Our study discloses a unique geroprotective pharmacological approach targeting DNA damage.

pathology↗

bioRxiv2023

FOXM1 expression reverts aging chromatin profiles through repression of the senescence-associated pioneer factor AP-1

Aging is characterized by changes in gene expression that drive deleterious cellular phenotypes leading to senescence. The transcriptional activation of senescence genes has been mainly attributed to epigenetic shifts, but the changes in chromatin accessibility and its underling mechanisms remain largely elusive in natural aging. Here, we profiled chromatin accessibility in human dermal fibroblasts (HDFs) from neonatal and octogenarian individuals. We found that AP-1 binding motifs are prevalent in elderly specific accessible regions of the chromatin while neonatal-specific regions are highly enriched for TEAD binding motifs. We further show that TEAD4 and FOXM1 share a conserved transcriptional regulatory landscape controlled by an age-dependent enhancer that closes with aging and drives senescence when deleted. Finally, we demonstrate that FOXM1 ectopic expression in elderly cells partially resets chromatin accessibility to a youthful state due to FOXM1 repressive function in the promoters of several members of the AP-1 complex. These results place FOXM1 at a top hierarchical level in chromatin remodeling required to prevent senescence.

genetics↗

bioRxiv2020

Cis-regulatory similarities in the zebrafish and human pancreas uncover potential disease-related enhancers

Introductory paragraphThe pancreas is a central organ for human diseases that have a dramatic societal burden, such as pancreatic cancer and diabetes1,2. Non-coding cis-regulatory elements (CREs) of DNA control gene expression3,4, being required for proper pancreas function. Most disease-associated alleles5,6 are non-coding, often overlapping with CREs5, suggesting that alterations in these regulatory sequences contribute to human pancreatic diseases by impairing gene expression. However, functional testing of CREs in vivo is not fully explored. Here we analysed histone modifications, transcription, chromatin accessibility and interactions, to identify zebrafish pancreas CREs and their human functional equivalents, uncovering disease-associated sequences across species. We found a human pancreatic enhancer whose deletion impairs the tumour suppressor gene ARID1A expression, conferring a potential tumour suppressor role to this non-coding sequence. Additionally, we identified a zebrafish ptf1a distal enhancer which deletion generates pancreatic agenesis, demonstrating the causality of this condition in humans7 and the interspecies functional equivalency of enhancers.

genomics↗