Biology subjects

Belmonte, J. C. I.

Publications and source records attributed to Belmonte, J. C. I..

6 recordsLinked to original sources

bioRxiv2026

Unwinding of RNA G-quadruplexes induces mouse and human totipotency

Totipotent stem cells (TotiSCs) have significant application prospects in regenerative medicine and assisted reproductive technologies. The mRNAs of totipotency-related genes are rich in G-quadruplex (G4) structures, while the G4 density of pluripotency-related genes mRNAs is relatively low, suggesting a potential functional link between RNA G4s and the totipotent state. Nevertheless, how G4s are involved in the establishment or maintenance of mouse and human totipotency remains poorly understood. Here, we demonstrate that FC3, a small-molecule RNA G4 unwinder, enables efficient induction and maintenance of mouse and human TotiSCs (mG4TotiSCs and hG4TotiSCs). These FC3-induced TotiSCs closely recapitulate the molecular features of 2-cell-stage blastomeres via transcriptomic and epigenomic profiling. Functionally, both mG4TotiSCs and hG4TotiSCs exhibit totipotent capacity: they differentiate into embryonic and extraembryonic lineages in vitro and in chimeric embryos; moreover, they autonomously self-organize into blastocyst-like structures without exogenous signalling. Mechanistically, we identify that Gata2 mRNA, a G4-containing transcript, is essential for FC3-mediated reprogramming. Genetic disruption of Gata2 would abolish totipotency induction. Collectively, RNA G4 unwinding is a new regulatory axis governing totipotency acquisition and maintenance, providing insight into the functional interplay between nucleic acid secondary structures and cell fate plasticity.

cell biology↗

bioRxiv2024

Multi-omic QTL mapping in early developmental tissues reveals phenotypic and temporal complexity of regulatory variants underlying GWAS loci

Most GWAS loci are presumed to affect gene regulation, however, only [~]43% colocalize with expression quantitative trait loci (eQTLs). To address this colocalization gap, we identify eQTLs, chromatin accessibility QTLs (caQTLs), and histone acetylation QTLs (haQTLs) using molecular samples from three early developmental (EDev) tissues. Through colocalization, we annotate 586 GWAS loci for 17 traits by QTL complexity, QTL phenotype, and QTL temporal specificity. We show that GWAS loci are highly enriched for colocalization with complex QTL modules that affect multiple elements (genes and/or peaks). We also demonstrate that caQTLs and haQTLs capture regulatory variations not associated with eQTLs and explain [~]49% of the functionally annotated GWAS loci. Additionally, we show that EDev-unique QTLs are strongly depleted for colocalizing with GWAS loci. By conducting one of the largest multi-omic QTL studies to date, we demonstrate that many GWAS loci exhibit phenotypic complexity and therefore, are missed by traditional eQTL analyses.

genomics↗

bioRxiv2023

Wiskott-Aldrich Syndrome Protein Regulates Nucleolar Organization and Function in Innate Immune Response

Wiskott-Aldrich syndrome (WAS) is a primary immunodeficiency disorder caused by the dysfunction of the WAS protein (WASP). Using an isogenic macrophage model derived from genome edited induced pluripotent stem cells we demonstrated that WASP functions in the nucleolus, which plays important roles in immune regulation. The absence of WASP resulted in smaller and misshapen nucleoli, decreased fibrillar center territory, and impaired ribosomal RNA (rRNA) transcription. The nucleolar and rRNA phenotypes were confirmed in WAS patient samples. Furthermore, WASP interacts with nucleolar proteins, including nucleophosmin 1 (NPM1) and fibrillarin (FBL). NPM1 deficiency is known to cause elevated cytokine expression following lipopolysaccharide (LPS) stimulation. Consistently, WASP deficient cells displayed lower levels of NPM1 and a heightened inflammatory cytokine response to LPS, which was rescued by overexpressing NPM1. Together, our research provides novel insights into the critical role of WASP in nucleolar function and the modulation of inflammatory cytokine production.

cell biology↗

bioRxiv2023

Building functional circuits in multispecies brains.

The genome is the ultimate architect of the brain. Its evolutionary variations build the neural circuits that endow each species with its innate senses and behaviors. A central question for neuroscience and translational medicine is whether neural circuits from two species can be made to function in an intact brain. Here, we establish genetic tools and use blastocyst complementation to selectively build and test interspecies neural circuits in rat-mouse brains. Despite [~]10-20 million years of evolution and prominent differences in brain size and cellular composition, rat pluripotent stem cells injected into mouse blastocysts widely populate and persist in the mouse brain. Unexpectedly, the mouse niche reprograms the birthdates of cortical and hippocampal rat neurons, where they also form synaptically active rat-mouse circuits. By genetically disabling host olfactory circuitry, we show that rat neurons restore synaptic information flow from the nose to the cortex. Rat neurons can also rescue a primal olfactory behavior (food-seeking), though less than mouse controls. By enabling a mouse to sense the world with rat neurons, we highlight the power of interspecies neural blastocyst complementation to uncover mechanisms of neural circuit development and evolution, and to inform efforts to rescue neural circuits affected by injury or disease.

developmental biology↗

bioRxiv2023

Therapeutic strategy for spinal muscular atrophy by combining gene supplementation and genome editing

Defect in the SMN1 gene causes spinal muscular atrophy (SMA), which shows loss of motor nerve cells, muscle weakness and atrophy. While current treatment strategies, including small molecules or viral vectors, have been reported to improve motor function and survival, an ultimate and long-term treatment to correct SMA endogenous mutations and improve its phenotypes is still highly challenging. We have previously developed a CRISPR-Cas9 based homology-independent targeted integration (HITI) strategy, which allowed for unidirectional DNA knock-in in both dividing and non-dividing cells in vivo. Here, we demonstrated its utility by correcting a SMA mutation in mice, and when combined with Smn1 cDNA supplementation show SMA long-term therapeutic benefits in mice. Our observations may provide new avenues for long term and efficient treatment of inherited diseases. SummaryThe Gene-DUET strategy by combining cDNA supplementation and genome editing was sufficient to ameliorate SMA phenotypes in mouse model in vivo.

bioengineering↗

bioRxiv2021

The Alzheimer's disease risk factor APOE4 drives pro-inflammation in human astrocytes via HDAC-dependent repression of TAGLN3

The Apolipoprotein E4 (APOE4) is the major allelic risk factor for late-onset Alzheimers disease (AD). APOE4 associates with a pro-inflammatory phenotype increasingly considered as critical in AD initiation and progression. Yet, the mechanisms driving an APOE4-dependent neuroinflammation remain unelucidated. Leveraging patient specific human induced Pluripotent Stem Cells (iPSCs) we demonstrate inflammatory chronicity and hyperactivated responses upon cytokines in human APOE4 astrocytes via a novel mechanism. We uncovered that APOE4 represses Transgelin 3 (TAGLN3), a new interacting partner of I{kappa}B, thus increasing the NF-kB activity. The transcriptional repression of TAGLN3 was shown to result from an APOE4-dependent histone deacetylase (HDAC) activity. The functional relevance of TAGLN3 was demonstrated by the attenuation of APOE4-driven neuroinflammation after TAGLN3 supplementation. Importantly, TAGLN3 downregulation was confirmed in the brain of AD patients. Our findings highlight the APOE4-TAGLN3 axis as a new pathogenic pathway that paves the way for the development of therapeutics to prevent maladaptive inflammatory responses in APOE4 carriers, while placing TAGLN3 downregulation as a potential biomarker of AD. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=98 HEIGHT=200 SRC="FIGDIR/small/440108v1_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@1036557org.highwire.dtl.DTLVardef@1f245bdorg.highwire.dtl.DTLVardef@c07c4aorg.highwire.dtl.DTLVardef@1200396_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗