Biology subjects

Martinez-sanchez, A.

Publications and source records attributed to Martinez-sanchez, A..

7 recordsLinked to original sources

bioRxiv2024

14-3-3ζ regulates adipogenesis by modulating chromatin accessibility during the early stages of adipocyte differentiation

We previously established the scaffold protein 14-3-3{zeta} as a critical regulator of adipogenesis and adiposity, but the temporal specificity of its action during adipocyte differentiation remains unclear. To decipher if 14-3-3{zeta} exerts its regulatory functions on mature adipocytes or on adipose precursor cells (APCs), we generated Adipoq14-3-3{zeta}KO and Pdgfra14-3-3{zeta}KO mouse models. Our findings revealed a pivotal role for 14-3-3{zeta} in APC differentiation in a sex-dependent manner, whereby male and female Pdgfra14-3-3{zeta}KO mice display impaired or potentiated weight gain, respectively, as well as fat mass. To better understand how 14-3-3{zeta} regulates the adipogenic transcriptional program in APCs, CRISPR-Cas9 was used to generate TAP-tagged 14-3-3{zeta}-expressing 3T3-L1 preadipocytes. Using these cells, we examined if the 14-3-3{zeta} nuclear interactome is enriched with adipogenic regulators during differentiation. Regulators of chromatin remodeling, such as DNMT1 and HDAC1, were enriched in the nuclear interactome of 14-3-3{zeta}, and their activities were impacted upon 14-3-3{zeta} depletion. The interactions between 14-3-3{zeta} and chromatin-modifying enzymes suggested that 14-3-3{zeta} may control chromatin remodeling during adipogenesis, and this was confirmed by ATAC-seq, which revealed that 14-3-3{zeta} depletion impacted the accessibility of up to 1,244 chromatin regions corresponding in part to adipogenic genes, promoters, and enhancers during the initial stages of adipogenesis. Moreover, 14-3-3{zeta}-dependent chromatin accessibility was found to directly correlate with the expression of key adipogenic genes. Altogether, our study establishes 14-3-3{zeta} as a crucial epigenetic regulator of adipogenesis and highlights the usefulness of deciphering the nuclear 14-3-3{zeta} interactome to identify novel pro-adipogenic factors and pathways.

physiology↗

bioRxiv2023

Abundant capped RNAs are derived from mRNA cleavage at 3'UTR G-Quadruplexes

The 3 untranslated region (3UTR) plays a crucial role in determining mRNA stability, localisation, translation and degradation. Cap analysis gene expression (CAGE), a method for the detection of capped 5 ends of mRNAs, additionally reveals a large number of apparently 5 capped RNAs derived from 3UTRs. Here we provide the first direct evidence that these 3UTR-derived RNAs are indeed capped and often more abundant than the corresponding full-length mRNAs. By using a combination of AGO2 enhanced individual nucleotide resolution UV crosslinking and immunoprecipitation (eiCLIP) and CAGE following siRNA knockdowns, we find that these 3UTR-derived RNAs likely originate from AGO2-mediated cleavage, and most often occur at locations with potential to form RNA-G-quadruplexes and are enriched by RNA-binding protein UPF1. High-resolution imaging and long-read sequencing analysis validates several 3UTR-derived RNAs, demonstrates their abundance and shows that they tend not to co-localise with the parental mRNAs. We also find that production of 3UTR-derived RNA could explain the previously reported role of a 3UTR G-quadruplex in regulating the production of APP protein. Taken together, we provide new insights into the origin and abundance of 3UTR-derived RNAs, show the utility of CAGE-seq for their quantitative detection, and provide a rich dataset for exploring new biology of a poorly understood new class of RNAs. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=73 SRC="FIGDIR/small/538568v3_ufig1.gif" ALT="Figure 1"> View larger version (15K): org.highwire.dtl.DTLVardef@3f2ca7org.highwire.dtl.DTLVardef@18ca1b6org.highwire.dtl.DTLVardef@1ccdd8dorg.highwire.dtl.DTLVardef@e58938_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2022

A transcriptomic signature for single pancreatic islet leader beta cells

AimsSpatially-organised increases in cytosolic Ca2+ within pancreatic beta cells in the pancreatic islet underlie the stimulation of insulin secretion by high glucose. Recent data have revealed the existence of subpopulations of beta cells including "leaders" which initiate Ca2+ waves. Whether leader cells possess unique molecular features, or localisation, is unknown. Main methodsHigh speed confocal Ca2+ imaging was used to identify leader cells and connectivity analysis, running under MATLAB and Python, to identify highly connected "hub" cells. To explore transcriptomic differences between beta cell sub-groups, individual leaders or followers were labelled by photo-activation of the cryptic fluorescent protein PA-mCherry and subjected to single cell RNA sequencing ("Flash-Seq"). Key findingsDistinct Ca2+ wave types were identified in individual islets, with leader cells present in 73 % (28 of 38 islets imaged). Scale-free, power law-adherent behaviour was also observed in 29% of islets, though "hub" cells in these islets did not overlap with leaders. Transcripts differentially expressed (295; padj<0.05) between leader and follower cells included genes involved in cilium biogenesis and transcriptional regulation. Functionally validating these findings, cilia number and length tended to be lower in leader vs follower cells. Leader cells were also located significantly closer to delta cells in Euclidian space than were follower cells. SignificanceThe existence of both a discrete transcriptome and unique localisation implies a role for these features in defining the specialized function of leaders. Specifically, these data raise the possibility of altered signalling from delta cells towards somatostatin receptors present on leader cell cilia.

cell biology↗

bioRxiv2021

Glucose-dependent miR-125b is a negative regulator of β-cell function

Impaired pancreatic {beta}-cell function and insulin secretion are hallmarks of type 2 diabetes. MicroRNAs are short non-coding RNAs that silence gene expression, vital for the development and function of {beta}-cells. We have previously shown that {beta}-cell specific deletion of the important energy sensor AMP-activated protein kinase (AMPK) results in increased miR-125b-5p levels. Nevertheless, the function of this miRNA in {beta}-cells is unclear. We hypothesized that miR-125b-5p expression is regulated by glucose and that this miRNA mediates some of the deleterious effects of hyperglycaemia in {beta}-cells. Here we show that islet miR-125b-5p expression is up-regulated by glucose in an AMPK-dependent manner and that short-term miR-125b-5p overexpression impairs glucose stimulated insulin secretion (GSIS) in the mouse insulinoma MIN6 cells and in human islets. An unbiased high-throughput screen in MIN6 cells identified multiple miR-125b-5p targets, including the transporter of lysosomal hydrolases M6pr and the mitochondrial fission regulator Mtfp1. Inactivation of miR-125b-5p in the human {beta}-cell line EndoC{beta}-H1 shortened mitochondria and enhanced GSIS, whilst mice overexpressing miR-125b-5p selectively in {beta}-cells (MIR125B-Tg) were hyperglycaemic and glucose intolerant. MIR125B-Tg {beta}-cells contained enlarged lysosomal structures and showed reduced insulin content and secretion. Collectively, we identify miR-125b as a glucose-controlled regulator of organelle dynamics that modulates insulin secretion. Graphical abstract O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY C_FIG_DISPLAY

molecular biology↗

bioRxiv2020

The long non-coding RNA Pax6os1/PAX6-AS1 modulates pancreatic β-cell identity and function.

Aim/HypothesisLong non-coding RNAs (lncRNAs) are emerging as crucial regulators of beta cell development and function. Here, we investigate roles for an antisense lncRNA expressed from the Pax6 locus (annotated as Pax6os1 in mice and PAX6-AS1 in humans) in beta cell identity and functionality. MethodsPax6os1 expression was silenced in MIN6 cells using siRNAs and changes in gene expression were determined by RNA sequencing or qRT-PCR. Mice inactivated for Pax6os1 and human PAX6-AS1-null EndoC-{beta}H1 cells, were generated using CRISPR/Cas9 technology. Human islets were infected with lentiviral vectors bearing a targeted shRNA or PAX6-AS1, which were used to silence or overexpress, respectively, the lncRNA. RNA sequencing or RT-qPCR were used to measure transcriptomic changes and RNA pulldown in mice and human cells followed by mass spectrometry/western blot were performed to explore RNA protein interactions. ResultsPax6os1/PAX6-AS1 expression was upregulated at high glucose concentrations in derived beta cell lines as well as in mouse and human islets, and in pancreatic islets isolated from mice fed a high fat diet (n=6, p=0.003) and patients with type 2 diabetes (n=11-5, p<0.01). Silencing or deletion of Pax6os1/PAX6-AS1 in MIN6 or EndoC-{beta}H1cells increased the expression of several {beta}-cell signature genes, including PDX1 and INS. Female, but not male, Pax6os1 null mice fed a high fat diet showed slightly enhanced glucose clearance. ShRNA-mediated silencing of PAX6-AS1 in human islets robustly increased INS mRNA, enhanced glucose-stimulated insulin secretion and calcium dynamics, while overexpression of the lncRNA exerted opposing effects. Pax6os1/AS-1 interacted with histones H3 and H4 in mouse and human cells, indicating a possible role for this lncRNA in histone modifications in both species. ConclusionsIncreased expression of PAX6-AS1 at high glucose levels may impair beta cell functionality and thus contribute to the development of type 2 diabetes. Thus, targeting PAX6-AS1 may provide a promising strategy to enhance insulin secretion and improve glucose homeostasis in this disease. Research in contextO_ST_ABSWhat is already known about the subject?C_ST_ABSLong non-coding RNAs (lncRNAs) are crucial components of the pancreatic islet regulome, whose misexpression may contribute to the development of diabetes. What is the key question?Is the lncRNA Pax6os1/PAX6-AS1 involved in beta cell functionality and type 2 diabetes? What are the new findings?The expression of Pax6os1/PAX6-AS1 is upregulated in mice fed a high fat diet and in pancreatic islets from type 2 diabetes donors. Overexpression of PAX6-AS1 in human pancreatic islets reduces insulin expression, glucose stimulated secretion and intracellular calcium dynamics. Silencing PAX6-AS1 in human pancreatic islets upregulates insulin expression, enhances glucose stimulated insulin secretion and increases intracellular calcium dynamics. How may this impact the clinic in the foreseeable future?Understanding the genetic factors induced by high glucose/obesity involved in beta cell dysfunction is crucial for the development of new therapies to treat T2D.

cell biology↗

bioRxiv2020

Reduced expression of TCF7L2 in adipocyte impairs glucose tolerance associated with decreased insulin secretion, incretins levels and lipid metabolism dysregulation in male mice

Transcription factor 7-like 2 (TCF7L2) is a downstream effector of the Wnt/beta-catenin signalling pathway and its expression is critical for adipocyte development. The precise role of TCF7L2 in glucose and lipid metabolism in adult adipocytes remains to be defined. Here, we aim to investigate how changes in TCF7L2 expression in mature adipocytes affect glucose homeostasis. Tcf7l2 was selectively ablated from mature adipocytes in C57BL/6J mice using an adiponectin promoter-driven Cre recombinase to recombine alleles floxed at exon 1 of the Tcf7l2 gene. Mice lacking Tcf7l2 in mature adipocytes displayed normal body weight. Male mice exhibited normal glucose homeostasis at eight weeks of age. Male heterozygote knockout mice (aTCF7L2het) exhibited impaired glucose tolerance (AUC increased 1.14 {+/-} 0.04 -fold, p=0.03), as assessed by intraperitoneal glucose tolerance test, and changes in fat mass at 16 weeks (increased by 1.4 {+/-} 0.09-fold, p=0.007). Homozygote knockout mice exhibited impaired oral glucose tolerance at 16 weeks of age (AUC increased 2.15 {+/-} 0.15-fold, p=0.0001). Islets of Langerhans exhibited impaired glucose-stimulated insulin secretion in vitro (decreased 0.54 {+/-} 0.13-fold aTCF7L2KO vs control, p=0.02), but no changes in in vivo glucose-stimulated insulin secretion. Female mice in which one or two alleles of the Tcf7l2 gene was knocked out in adipocytes displayed no changes in glucose tolerance, insulin sensitivity or insulin secretion. Plasma levels of glucagon-like peptide-1 and gastric inhibitory polypeptide were lowered in knockout mice (decreased 0.57 {+/-} 0.03-fold and 0.41 {+/-} 0.12-fold, p=0.04 and p=0.002, respectively), whilst plasma free fatty acids and Fatty Acid Binding Protein 4 circulating levels were increased by 1.27 {+/-} 0.07 and 1.78 {+/-} 0.32-fold, respectively (p=0.05 and p=0.03). Mice with biallelic Tcf7l2 deletion exposed to high fat diet for 9 weeks exhibited impaired glucose tolerance (p=0.003 at 15 min after glucose injection) which was associated with reduced in vivo glucose-stimulated insulin secretion (decreased 0.51 {+/-} 0.03-fold, p=0.02). Thus, our data indicate that loss of Tcf7l2 gene expression in adipocytes leads to impairments on metabolic responses which are dependent on gender, age and nutritional status. Our findings further illuminate the role of TCF7L2 in the maintenance of glucose homeostasis.

physiology↗

bioRxiv2020

High throughput identification of miR-145 targets in human articular chondrocytes

ObjectiveMicroRNAs play a key role in biological processes, including cartilage development and homeostasis and are dysregulated in many diseases, including osteoarthritis. MiR-145 modulation induces profound changes in the human articular chondrocyte (HAC) phenotype, partially through direct repression of SOX9. Since miRNAs can simultaneously silence multiple targets, we aimed to identify the whole targetome of miR-145 in HACs. This information is critical if miR-145 is to be considered a target for cartilage repair. MethodsRIP-seq (RNA-immunoprecipitation plus HT-sequencing) of miRISC (miRNA-induced silencing complex) was performed in HACs overexpressing miR-145 to identify miR-145 direct targets. The motif discovery method cWords was used to assess enrichment on miR-145 seed matches in the identified targets. RT-qPCR, Western (immuno-)blot and luciferase assays were used to validate miRNA-target interactions. ResultsMiR-145 overexpression affects the expression of over 350 genes and directly targets more than 50 mRNAs through the 3UTR or, more commonly, the coding region. We also demonstrate that miR-145 targets DUSP6, involved in cartilage organization and development, at the translational level. DUSP6 depletion using specific siRNAs lead to MMP13 up-regulation, suggesting that miR-145-mediated DUSP6 depletion contributes to the effect of miR-145 on MMP13 expression. ConclusionWe demonstrate that miR-145 directly targets several genes in primary chondrocytes including those involved in the expression of the extracellular matrix and inflammation. Thus, we propose miR-145 as an important regulator of chondrocyte function and a new target for cartilage repair.

cell biology↗