Biology subjects

Rodriguez, T. A.

Publications and source records attributed to Rodriguez, T. A..

8 recordsLinked to original sources

bioRxiv2026

Mitochondrial activity directs nutrient uptake and patterning in human gastrula models.

How a uniform field of cells responds to inductive cues to form distinct, spatially organised, lineages is a question of much interest. In human gastruloids, a BMP4 signalling gradient directs the self-organization of embryonic stem cells (hESCs) into the three germ-layers. But what regulates differential responses to BMP4 is poorly understood. Here we demonstrate that mitochondrial activity is key, as by directing nutrient uptake it determines the threshold of BMP signalling. We show that decreased mitochondrial activity stimulates fatty acid uptake via macropinocytosis and subsequent {beta}-oxidation and that this increases the BMP4 response. However, we also find that disease causing mitochondrial DNA mutations impair dynamic switching between glucose and fatty acid utilisation, causing hESCs to be unable to spatially organise the mesoderm, endoderm and ectoderm layers in gastruloids. These results suggest that the correct interpretation of morphogen gradients during gastrulation emerges through the crosstalk of signalling inputs and nutrient utilisation.

developmental biology↗

bioRxiv2026

MTFP1 preserves β-cell cristae structure and bioenergetics to ensure insulin release and glucose homeostasis

Pancreatic {beta}-cells are uniquely dependent on mitochondrial metabolism to couple glucose sensing to insulin secretion, a process impaired in diabetes. Mitochondrial fission process 1 (MTFP1) is an inner mitochondrial membrane protein that plays pleiotropic, tissue-specific roles in mitochondrial function and dynamics. Our previous work has identified Mtfp1 mRNA as a target for miR-125b, a microRNA that negatively regulates insulin secretion from {beta}-cells. Nevertheless, the function of MTFP1 in these cells remained unexplored. Here, we show that MTFP1 is essential for normal glucose-stimulated insulin secretion (GSIS) in mouse and human cell lines and islets, and that mice with {beta}-cell-specific elimination of MTFP1 develop glucose intolerance. Whereas {beta}-cell survival and mitochondrial content were unaffected, oxidative phosphorylation and ATP production were sharply lowered. These changes were accompanied by disruption of mitochondrial cristae structure and a reduced contact surface with the endoplasmic reticulum, providing a mechanistic basis for defective stimulus-secretion coupling. Conversely, MTFP1 overexpression in mouse and human islets sufficed to improve mitochondrial respiration and GSIS. Finally, MTFP1 downregulation blocked the positive effects of miR-125b elimination in GSIS and mitochondrial respiration, unveiling MTFP1 as a downstream effector of miR-125b. Together, our findings identify MTFP1 as a critical regulator of {beta}-cell mitochondrial architecture and function, necessary for efficient insulin secretion and glucose homeostasis, and a potential therapeutic target to enhance {beta}-cell bioenergetic resilience in diabetes.

cell biology↗

bioRxiv2024

Sensing of extracellular L-Proline availability by the integrated stress response determines the outcome of cell competition.

Cell competition is a quality control acting from development to the adult that eliminates cells that are less-fit than their neighbours. How winner cells induce the elimination of losers during this process is poorly understood. Here, we address this question by studying the onset of differentiation in mouse, where cell competition eliminates 35% of embryonic cells. These loser cells have mitochondrial dysfunction, and we find that this causes amino-acid deprivation and activation of the integrated stress response (ISR), a pathway essential for their survival. We show that L-Proline is a key amino-acid sensed by the ISR and that in a competitive environment, winner cells induce increased L-Proline uptake in loser cells. This causes ISR repression and their elimination. Our results imply that cell competition is acting as a nutrient sensor, eliminating dysfunctional cells when amino acids are plentiful but sparing them in nutrient poor environments.

developmental biology↗

bioRxiv2022

Levels of p53 expression determine the competitive ability of embryonic stem cells during the onset of differentiation.

During development, the rate of tissue growth is determined by the relative balance of cell division and cell death. Cell competition is a fitness quality control mechanism that contributes to this balance by eliminating viable cells that are less-fit than their neighbours. What mutations confer cells with a competitive advantage or the dynamics of the interactions between winner and loser cells are not well understood. Here, we show that embryonic cells lacking the tumour suppressor p53 are super-competitors that eliminate their wild-type neighbours through the direct induction of apoptosis. This elimination is context dependant, as does not occur when cells are pluripotent and is triggered by the onset of differentiation. Furthermore, by combining mathematical modelling and cell-based assays we show that the elimination of wild-type cells is not through a competition for space or nutrients, but instead is mediated by short range interactions that are dependent on the local cell neighbourhood. This highlights the importance of the local cell neighbourhood and the competitive interactions within this neighbourhood for the regulation of proliferation during early embryonic development.

developmental biology↗

bioRxiv2020

Pancreatic beta cell selective deletion of mitofusins 1 and 2 (Mfn1 and Mfn2) disrupts mitochondrial architecture and abrogates glucose-stimulated insulin secretion in vivo

Aims/hypothesisMitochondrial glucose metabolism is essential for stimulated insulin release from pancreatic beta cells. Whether mitochondrial networks may be important for glucose or incretin sensing has yet to be determined. MethodsHere, we generated mice with beta cell-selective, adult-restricted deletion of the mitofusin genes Mfn1 and Mfn2 ({beta}Mfn1/2 dKO). Whole or dissociated pancreatic islets were used for live beta cell fluorescence imaging of cytosolic or mitochondrial Ca2+ concentration and ATP production or GSIS in response to increasing glucose concentrations or GLP-1 receptor agonists. Serum and blood samples were collected to examine oral and i.p. glucose tolerance. Results{beta}Mfn1/2 dKO mice displayed elevated fed and fasted glycaemia (p<0.01, p<0.001) and a >five-fold decrease (p<0.0001) in plasma insulin. Mitochondrial length, glucose-induced polarisation, ATP synthesis and cytosolic Ca2+ increases were all reduced (p<0.05,p<0.01,p<0.0001) in dKO islets, and beta cell Ca2+ dynamics were suppressed in vivo (p<0.001). In contrast, oral glucose tolerance was near normal in {beta}Mfn1/2 dKO mice (p<0.05, p<0.01) and GLP-1 or GIP receptor agonists largely corrected defective GSIS from isolated islets through an EPAC-dependent signalling activation. Conclusions/interpretationMitochondrial fusion and fission cycles are thus essential in the beta cell to maintain normal glucose, but not incretin, sensing. Defects in these cycles in some forms of diabetes might therefore provide opportunities for novel incretin-based or other therapies. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=180 SRC="FIGDIR/small/055384v3_ufig1.gif" ALT="Figure 1"> View larger version (38K): org.highwire.dtl.DTLVardef@258053org.highwire.dtl.DTLVardef@c07cborg.highwire.dtl.DTLVardef@1d3bb1forg.highwire.dtl.DTLVardef@1a1f128_HPS_FORMAT_FIGEXP M_FIG Impact of Mfn1/2 deletion on glucose and incretin stimulated-insulin secretion in beta cells. (A) In control animals, glucose is taken up by beta cells through GLUT2 and metabolised by mitochondria (elongated structure) through the citrate (TCA) cycle, leading to an increased mitochondrial proton motive force (hyperpolarised {Delta}{psi}m), accelerated ATP synthesis and O2 consumption rate (OCR). Consequently, the cytoplasmic ATP:ADP ratio rises, which causes closure of KATP channels, depolarisation of plasma membrane potential ({psi}m), opening of VDCCs and influx of cytosolic Ca2+. Elevated [Ca2+]cyt triggers a number of ATP-dependent processes including insulin secretion and improved beta-beta cell communication through connexin 36 (Cx36). (B) Following Mfn1/2 deletion (Mfn1/2 dKO), highly fragmented mitochondria were associated with reduced mitochondrial Ca2+ ([Ca2+]m) accumulation, leading to a less polarised {Delta}{psi}m, weaker OCR, lower mtDNA copy number and decreased ATP synthesis. This is expected to result in weaker {psi}m depolarisation, cytosolic Ca2+ influx and beta-beta cell connectivity due to lower expression of Cx36. Despite observing a higher number of docked insulin granules on the plasma membrane, insulin secretion was highly suppressed in these animals. This was also associated with increased beta cell death and reduced beta cell mass. (C) In response to incretins, insulin secretion is potentiated through the activation of GLP1-R and cAMP signalling involving PKA- and EPAC2-dependent pathways. Elevated [Ca2+]cyt triggers a number of ATP-dependent processes including insulin secretion and Ca2+ removal into the endoplasmic reticulum (ER).(D) In Mfn1/2 dKO cells, activation of the GLP1-R was shown to be linked with a potentiation of the EPAC2 pathway that is PKA independent, along with an increased ER Ca2+ uptake and improved beta-beta cell communication. How these amplifying signals of glucose metabolism for insulin secretion are linked with fragmented mitochondria remains unknown. Red and bold arrows represent enhanced pathways; dashed arrows represent impaired pathways. This figure was produced using illustrations from Servier Medical Art, http://smart.servier.com/ C_FIG Research in contextWhat is already known about this subject? Mitochondrial ultrastructural variations and number are altered in beta cells of human T2D patients [1]. Mice lacking Opa1, which controls mitochondrial fusion and inner membrane cristae structure, in beta cells, develop hyperglycaemia and defects in GSIS [2]. What is the key question? Is an interconnected mitochondrial network essential in primary mouse beta cells for normal insulin secretion and glucose homeostasis? What are the new findings? We generated mice with beta cell-selective, adult-restricted deletion of the mitofusin genes Mfn1 and Mfn2 and show that insulin secretion and glucose homeostasis are strongly reduced in vivo. Cytosolic and mitochondrial Ca2+ increases, {Delta}{psi}m, ATP production and beta cell connectivity are impaired in {beta}Mfn1/2 dKO animals. Incretins bypass the above defects through an exchange protein directly activated by cAMP (EPAC)-dependent signalling mechanism. How might this impact on clinical practice in the foreseeable future? The ability of incretins to bypass defects in mitochondrial function might be exploited by the design of new agonists which target this pathway.

molecular biology↗

bioRxiv2020

Differences in mitochondrial activity trigger cell competition during early mouse development.

Cell competition is emerging as a quality control mechanism that eliminates unfit cells in a wide range of settings from development to the adult. However, the nature of the cells normally eliminated by cell competition and what triggers their elimination remains poorly understood. In mouse, prior to gastrulation 35% of epiblast cells are eliminated. Here we have performed single cell transcriptional profiling of these cells and find that they show the hallmarks of cell competition and have mitochondrial defects. We demonstrate that mitochondrial defects are common to a range of different loser cell types and that manipulating mitochondrial function is sufficient to trigger competition. Importantly, we show that in the embryo cell competition eliminates cells with mitochondrial DNA mutations and that even non-pathological changes in mitochondrial DNA sequence can induce cell competition. Our results therefore suggest that cell competition is a purifying selection that optimises mitochondrial performance prior to gastrulation.

developmental biology↗

bioRxiv2019

Genetically variant human pluripotent stem cells selectively eliminate wild-type counterparts through YAP-mediated cell competition

The appearance of genetic changes in human pluripotent stem cells (hPSCs) presents a concern for their use in research and regenerative medicine. Variant hPSCs harbouring recurrent culture-acquired aneuploidies display growth advantages over wild-type diploid cells, but the mechanisms yielding a drift from predominantly wild-type to variant cell populations remain poorly understood. Here we show that the dominance of variant clones in mosaic cultures is enhanced through competitive interactions resulting in elimination of wild-type cells. This elimination occurs through corralling and mechanical compression by faster growing variants, causing a redistribution of F-actin and sequestration of YAP in the cytoplasm that induces apoptosis in wild-type cells. Importantly, YAP overexpression in wild-type cells is sufficient to alleviate their loser phenotype. Our results demonstrate that hPSC fate is coupled to mechanical cues imposed by neighbouring cells and reveal that hijacking this mechanism allows variants to achieve clonal dominance in cultures.

cell biology↗

bioRxiv2019

DRP1-mediated regulation of mitochondrial dynamics determines the apoptotic response upon embryonic differentiation.

The changes that drive differentiation create a large potential for the emergence of abnormal cells that need to be removed before they contribute to further development or the germline. This removal is in part achieved by cells becoming hypersensitive to death upon exit of naive pluripotency. What causes this change in apoptotic response is unknown. Here we identify that it is controlled by the regulator of mitochondrial dynamics DRP1. We show that in mouse, naive pluripotent cells have fragmented mitochondria due to high DRP1-mediated fission, but upon differentiation, DRP1 activity decreases, inducing mitochondria to fuse and form complex networks. We demonstrate that this decrease in DRP1 activity lowers the apoptotic threshold, as mutation of DRP1 increases the sensitivity to cell death and its over-expression protects against apoptosis. Together, our findings highlight how regulation of mitochondrial dynamics allows cells to adapt their apoptotic response to the changing environment of differentiation.

developmental biology↗