Biology subjects

Velasco, I.

Publications and source records attributed to Velasco, I..

5 recordsLinked to original sources

bioRxiv2026

Rhizobacterial Biosensors Spatially Map Natural and Engineered Sucrose Exudation

Root exudation mediates the delivery of plant primary and secondary metabolites into soil, where they regulate plant-microbe interactions and terrestrial carbon cycling. Conventional exudate analyses quantify total root-released carbon yet obscure the spatial origin and rhizosphere influence of individual compounds. Here, we develop a rhizobacterial biosensor platform, named Suc-MAPP, to map local exudate profiles along the surface of colonized root tissues. Focusing on sucrose, we engineered sfGFP-based, sucrose-responsive gene circuits in Pseudomonas putida KT2440 for live imaging of exudate concentrations in the micromolar range. These biosensors reveal spatially structured sucrose exudation patterns across eudicots and monocots and implicate photoassimilated source-sink dynamics as a major determinant. We further apply this platform to phenotype exudation modulated by synthetic gene circuitry in Arabidopsis thaliana, identifying genetic design rules for graded sucrose release and quantifying how engineered export sculpts rhizosphere assembly of a defined bacterial community. Together, these results establish programmable rhizobacterial biosensors as tools to spatially resolve plant-environment carbon exchange in situ and provide a framework for extending this approach to diverse exudate targets.

synthetic biology↗

bioRxiv2025

Ablation of microglial estrogen receptor alpha predisposes to diet-induced obesity in male mice

Estrogen receptor alpha (ER) signaling has metabolic and anti-inflammatory properties in addition to its impact on reproductive function. In male but not female mice, inflammatory activation of microglia, the resident macrophages of the brain, has been implicated in the pathogenesis of diet-induced obesity (DIO), raising the possibility that differences in microglial estrogen signaling may account for the sexual dimorphism. In this study, we assessed metabolic and CNS histopathological properties in a mouse model with inducible microglia-specific ablation of ER (MG-ERKO). Male MG-ERKO mice developed increased weight gain and insulin resistance relative to controls during high-fat diet (HFD) feeding. Indirect calorimetry analysis revealed that reduced energy expenditure was the main driver of the obese phenotype. In contrast, female MG-ERKO mice fed HFD developed mild insulin resistance with no change in body weight gain compared to controls. Immunohistochemical analyses of the microglial activation marker IBA1 in the mediobasal hypothalamus (MBH) revealed that female MG-ERKO mice had an increased number of microglia without showing morphological signs of activation. In contrast, MBH microglial number was unchanged in MG-ERKO male mice, but the cells adopted more activated morphological profiles. Finally, HFD-fed MG-ERKO male mice had increased POMC neuron-microglia interactions but fewer overall hypothalamic POMC neurons, suggesting microglia may disrupt POMC neuron integrity to promote DIO. Together, these findings indicate that sex-specific actions of estrogen in microglia limit the metabolic complications of HFD feeding.

neuroscience↗

bioRxiv2025

Identification of enhancer chromatin signatures involved in dopaminergic induction through multi-omics analysis

The establishment of precise transcriptional programs during neuronal development depends on a complex and dynamic landscape of regulatory elements. Here, we combined histone modification ChIP-seq, chromatin accessibility profiling, and transcriptomics to map active enhancer repertoires during the differentiation of human embryonic stem cells into midbrain dopaminergic neurons. Our integrative analysis revealed thousands of stage-specific enhancers, over half of which were previously unannotated, and uncovered coordinated chromatin and transcriptional transitions linking pluripotency exit to neuronal lineage commitment. Functional enrichment of enhancer-linked target genes delineated distinct regulatory programs, pluripotency maintenance in undifferentiated cells and midbrain specification in differentiated neuron, while transcription factor motif analysis identified regulatory modules, including a dopaminergic-specific RFX4 network. We further characterized enhancer-gene relationships showing concordant changes in chromatin state and expression for neuronal genes, suggesting enhancer-driven control of dopaminergic identity. These findings provide a genome-scale framework for interpreting how dynamic enhancer landscapes encode developmental fate decisions in the human nervous system.

genomics↗

bioRxiv2022

Dissecting the KNDy hypothesis: KNDy neuron-derived kisspeptins are dispensable for puberty but essential for preserved female fertility and gonadotropin pulsatility

Kiss1 neurons in the hypothalamic arcuate-nucleus (ARC) play key roles in the control of GnRH pulsatility and fertility. A fraction of ARC Kiss1 neurons, termed KNDy, co-express neurokinin B (NKB; encoded by Tac2). Yet, NKB- and Kiss1-only neurons are also found in the ARC, while a second major Kiss1-neuronal population is present in the rostral hypothalamus. The specific contribution of different Kiss1 neuron sub-sets to reproductive control remains unfolded. To tease apart the physiological roles of KNDy-born kisspeptins, conditional ablation of Kiss1 in Tac2-expressing cells was implemented in vivo. Mice with Tac2 cell-specific Kiss1 KO (TaKKO) displayed reduced ARC kisspeptin content and Kiss1 expression, with greater suppression in females, which was detectable at infantile-pubertal age. In contrast, Tac2/NKB levels were fully preserved. Despite the drop of ARC Kiss1/kisspeptin, pubertal timing was normal in TaKKO mice of both sexes. However, young-adult TaKKO females displayed disturbed LH pulsatility and sex steroid levels, with suppressed basal LH and pre-ovulatory LH surges, early-onset subfertility and premature ovarian insufficiency. Conversely, testicular histology and fertility were grossly conserved in TaKKO males. Ablation of Kiss1 in Tac2-cells led also to sex-dependent alterations in body composition, glucose homeostasis and locomotor activity. Our data document that KNDy-born kisspeptins are dispensable/compensable for puberty in both sexes, but required for maintenance of female gonadotropin pulsatility and fertility, as well as adult metabolic homeostasis. Significance StatementNeurons in the hypothalamic arcuate nucleus (ARC) co-expressing kisspeptins and NKB, named KNDy, have been recently suggested to play a key role in pulsatile secretion of gonadotropins, and hence reproduction. However, the relative contribution of this Kiss1 neuronal-subset, vs. ARC Kiss1-only and NKB-only neurons, as well as other Kiss1 neuronal populations, has not been assessed in physiological settings. We report here findings in a novel mouse-model with elimination of KNDy-born kisspeptins, without altering other kisspeptin compartments. Our data highlights the heterogeneity of ARC Kiss1 populations and document that, while dispensable/compensable for puberty, KNDy-born kisspeptins are required for proper gonadotropin pulsatility and fertility, specifically in females. Characterization of this functional diversity is especially relevant, considering the potential of kisspeptin-based therapies for management of human reproductive disorders. Disclosure StatementThe authors have nothing to disclose in relation to the contents of this work.

physiology↗

bioRxiv2019

Tetrahydrocannabinolic Acid A (THCA-A) Reduces Adiposity And Prevents Metabolic Disease Caused By Diet-Induced Obesity

Cannabis has remarkable therapeutic potential, but its clinical use is limited by the psychotropic activity of {Delta}9-tetrahydrocannabinol ({Delta}9-THC). Surprisingly, the biological profile of the non-narcotic native precursor of {Delta}9-THC ({Delta}9-THC acid A, {Delta}9-THCA-A) is still largely unexplored. We present evidence that {Delta}9-THCA-A is a partial and selective PPAR{gamma} modulator, endowed with lower adipogenic activity than the full PPAR{gamma} agonist rosiglitazone (RGZ) and with an enhanced osteoblastogenic activity in human mesenchymal stem cells. Docking and in vitro functional assays indicated that {Delta}9-THCA-A binds to and activates PPAR{gamma} by acting at both the canonical and the alternative sites of the ligand-binding domain. Transcriptomic signatures at inguinal white adipose tissue (iWAT) from mice treated with {Delta}9-THCA-A confirmed its mode of action on PPAR{gamma}. Administration of {Delta}9-THCA-A in a mouse model of high fat diet (HFD)-induced obesity significantly reduced fat mass and body weight gain, markedly ameliorating glucose intolerance and insulin resistance, and largely preventing liver steatosis, adipogenesis and macrophage infiltration in fat tissues. Additionally, immunohistochemistry, transcriptomic, and plasma biomarker analyses showed that treatment with {Delta}9-THCA-A caused browning of iWAT and displayed potent anti-inflammatory actions in HFD mice. Altogether, our data validate the potential of {Delta}9-THCA-A as a low adipogenic PPAR{gamma} agonist, capable of substantially improving the symptoms of obesity-associated metabolic syndrome and inflammation. These findings suggest that {Delta}9-THCA-A, and perhaps non-decarboxylated Cannabis sativa extracts, are worth considering for addition to our inventory of cannabis medicines.\n\nSIGNIFICANCE STATEMENTThe medicinal use of Cannabis is gaining momentum, despite the adverse psychotropic effects of {Delta}9-THC, the decarboxylation product of its naturally occurring and non-psychotropic precursor {Delta}9-THCA-A. We present evidence that {Delta}9-THCA-A is a partial ligand agonist of PPAR{gamma} with lower adipogenic activity compared to the full PPAR{gamma} agonist rosiglitazone (RGZ). Moreover, chronic administration of {Delta}9-THCA-A in a mouse model of high fat diet (HFD)-induced obesity significantly reduced body weight gain and fat mass, improved glucose intolerance and insulin resistance, and prevented liver steatosis and macrophage infiltration in fat tissues, additionally inducing white adipose tissue browning. Collectively, these observations qualify {Delta}9-THCA-A, a compound devoid of psychotropic effects, as an efficacious pharmacological agent to manage metabolic syndrome and obesity-associated inflammation.\n\nHighlights- {Delta}9-THCA-A is a partial PPAR{gamma} ligand agonist with low adipogenic activity\n- {Delta}9-THCA-A enhances osteoblastogenesis in bone marrow derived mesenchymal stem cells.\n- {Delta}9-THCA-A reduces body weight gain, fat mass, and liver steatosis in HFD-fed mice\n- {Delta}9-THCA-A improves glucose tolerance, insulin sensitivity, and insulin profiles in vivo\n- {Delta}9-THCA-A induces browning of iWAT and has a potent anti-inflammatory activity

pharmacology and toxicology↗