Biology subjects

Sanz, E.

Publications and source records attributed to Sanz, E..

13 recordsLinked to original sources

bioRxiv2025

Sex-dependent hypothalamic microinflammation and microglial polarization: The role of JNK in high-fat diet-induced insulin resistance

Obesity and its associated metabolic disorders, including insulin resistance and type 2 diabetes, are major global health challenges. Early hypothalamic microinflammation is emerging as a key contributor to the onset of metabolic dysfunction, but its temporal dynamics, underlying mechanisms, and sex-specific differences remain unclear. Here, we examined the effects of short-term high-fat diet (HFD) exposure on hypothalamic microinflammation, glial activation, and insulin signaling in male and female mice. Males rapidly developed hypothalamic microinflammation, characterized by increased pro-inflammatory cytokines, reactive gliosis, and impaired insulin signaling, whereas females did not show these alterations. Interestingly, we also observed a sex-specific pattern in microglial M2 polarization: females maintained a sustained M2 response throughout the experimental period, while males exhibited only a transient peak that declined in the following days. These sex-specific differences in microglial dynamics and polarization may be linked to the c-Jun N-terminal kinase pathway, a classical mediator of inflammatory signaling. To further explore this, we analyzed mice lacking JNK3, the CNS-enriched isoform of JNK. Loss of JNK3 disrupted early microglial polarization, abolished the transient M2 response, and predisposed males to enhanced gliosis and partial hypothalamic insulin resistance, while females retained partial resilience. These findings indicate that JNK3 contributes to the regulation of microglial dynamics and polarization in response to metabolic stress. Overall, our study highlights a sex-dependent role of microglia and JNK in shaping early hypothalamic microinflammation and central insulin sensitivity, providing potential targets for intervention in obesity-associated metabolic disease.

neuroscience↗

bioRxiv2025

Cell-Intrinsic Vulnerability and Immune Activation Cooperate to Drive Degeneration in a Mitochondrial Complex I Deficiency Model of Optic Neuropathy

Mitochondrial dysfunction is a central hallmark of many optic neuropathies, yet the mechanisms linking intrinsic metabolic stress to retinal ganglion cell (RGC) degeneration remain unclear. To bridge this gap, we developed conditional transgenic models targeting the mitochondrial complex I subunit Ndufs4 in the retina. Broad deletion of Ndufs4 in the retina resulted in vision loss, progressive RGC degeneration, and pronounced immune activation before overt RGC death. Strikingly, depletion of myeloid cells significantly preserved RGCs, demonstrating that inflammation is not simply a downstream consequence but a participant in the degeneration process. To further distinguish between intrinsic and extrinsic mechanisms, we generated a mosaic model in which only subsets of retinal cells lacked Ndufs4. In this paradigm, the degeneration first appeared selectively in mutant regions, suggesting that mitochondrial impairment within RGCs is necessary to initiate vulnerability. At later stages, however, the degeneration extended beyond mutant territories, highly suggestive of a propagation through non-cell autonomous processes. Together, these findings support a model in which mitochondrial dysfunction creates the conditions for neuronal vulnerability, while immune responses govern the timing and extent of cell loss. This framework explains the consistent co-occurrence of metabolic deficits and neuroinflammation in optic neuropathies and highlights the importance of their interactions in disease progression. By clarifying the intersection of intrinsic and extrinsic mechanisms, this work advances our understanding of RGC degeneration and provides a conceptual basis for deciphering pathogenic processes across diverse optic neuropathies.

neuroscience↗

bioRxiv2025

Predicting Saturation Concentrations of Phase-Separating Proteins via Thermodynamic Integration

Phase separation of proteins and nucleic acids into biomolecular condensates contributes to the regulation of cellular compartmentalisation in membrane-less environments. A key parameter controlling the onset of biomolecular condensate formation via liquid--liquid phase separation is the saturation concentration (Csat)-- the threshold concentration above which condensation takes place. While measuring Csat for protein solutions in vitro is experimentally accessible, determining this quantity in simulations remains challenging due to the extremely low equilibrium concentrations at which many proteins phase separate. This occurs because the gold standard in simulations consists on combining a residue-resolution coarse-grained model with the Direct Coexistence simulation method, which yields poor estimates of the equilibrium concentrations of the dilute phase due to lack of statistics. In this work, we present two independent thermodynamic integration (TI) schemes which, when combined with Direct Coexistence simulations, enable accurate calculation of saturation concentrations and phase diagrams--facilitating direct comparison with experimental measurements across a wide range of conditions. Our methods, combined with the Mpipi-Recharged residue-resolution coarse-grained model, accurately estimate Csat for a wide range of intrinsically disordered and multi-domain proteins, including disease-associated RNA- and DNA-binding proteins involved in the formation of stress granules and P granules, as well as engineered mutants of hnRNPA1. Furthermore, we compare our TI methods against a computationally efficient machine-learning predictor trained to estimate saturation concentrations at sub-physiological temperatures. While both approaches yield realistic predictions, explicit molecular dynamics simulations enable the calculation of complete phase diagrams and provide insight into the molecular mechanisms and interactions driving phase-separation. Overall, our approach offers a robust, physically grounded framework for improving and validating coarse-grained models of biomolecular phase behaviour, effectively bridging the gap between simulation and experiment.

biophysics↗

bioRxiv2024

Expression of sex steroid receptors and sex differences of Otp glutamatergic neurons of the medial extended amygdala

The medial extended amygdala (EAme) is part of the social behavior network and its subdivisions show expression of sex steroid receptors, which participate in the regulation of sexually dimorphic behaviors. However, EAme subdivisions are highly heterogeneous in terms of neuron subtypes, with different subpopulations being involved in regulation of different aspects of social and non-social behaviors. To further understand the role of the different EAme neurons and their contribution to sexual differences, here we studied one of its major subtypes of glutamatergic neurons, those derived from the telencephalon-opto-hypothalamic domain that coexpress Otp and Foxg1 genes during development. Our results showed that the vast majority of the Otp glutamatergic neurons of the medial amygdala and BSTM in both sexes express Ar, Esr1 (ER) and Esr2 (ER{beta}) mRNA. Moreover, the high percentage of receptors expression in the Otp neurons (between 93 and 100%) indicates that probably the majority of the Otp neurons of EAme are coexpressing the three receptors. In addition, Otp neurons of the posterodorsal medial amygdala have a larger soma and occupy more space in males than in females. These and other features of the Otp neurons regarding their expression of sex steroid receptors likely contribute to some of the sexually-dimorphic behaviors regulated by EAme.

neuroscience↗

bioRxiv2024

Dysfunctional LHX6 pallido-subthalamic projections mediate epileptic events in a mouse model of Leigh Syndrome

Deficits in the mitochondrial energy-generating machinery cause mitochondrial disease (MD), a group of untreatable and usually fatal disorders. Among many severe symptoms, refractory epileptic events are a common neurological presentation of MD. However, the neuronal substrates and circuits for MD-induced epilepsy remain unclear. Here, using mouse models of mitochondrial epilepsy that lack mitochondrial complex I subunit NDUFS4 in a constitutive or conditional manner, we demonstrate that mitochondrial dysfunction leads to a reduction in the number of GABAergic neurons in the rostral external globus pallidus (GPe) and identify a specific affectation of pallidal Lhx6-expressing inhibitory neurons. Our findings further reveal that viral vector-mediated Ndufs4 re-expression in the GPe effectively prevents seizures and improves the survival in the models. Additionally, we highlight the subthalamic nucleus (STN) as a critical structure in the neural circuit involved in mitochondrial epilepsy, as its inhibition effectively reduces epileptic events. Thus, we have identified a novel role for pallido-subthalamic projections in the development of epilepsy in the context of mitochondrial dysfunction. Our results suggest STN inhibition as a potential therapeutic intervention for refractory epilepsy in patients with MD providing new leads in the quest to identify novel and effective treatments.

neuroscience↗

bioRxiv2024

Phase behaviour of hnRNPA1 low-complexity domain mutants described by different sequence-dependent models

Intracellular liquid-liquid phase separation (LLPS) of proteins and nucleic acids is a fundamental mechanism by which cells compartmentalize their components and perform essential biological functions. Molecular simulations play a crucial role in providing microscopic insights into the physicochemical processes driving this phenomenon. In this study, we systematically compare six state-of-the-art sequence-dependent, residue-resolution models to evaluate their performance in reproducing the phase behaviour and material properties of condensates formed by seven variants of the low-complexity domain (LCD) of the hnRNPA1 protein (A1-LCD)--a protein implicated in the pathological liquid-to-solid transition of stress granules. Specifically, we assess the HPS, HPS-cation-{pi}, HPS-Urry, CALVADOS2, Mpipi, and Mpipi-Recharged models in their predictions of the condensate saturation concentration, critical solution temperature, and condensate viscosity for the A1-LCD variants. Our analyses demonstrate that, among the tested models, Mpipi, Mpipi-Recharged, and CALVADOS2 provide accurate descriptions of the critical solution temperatures and saturation concentrations for the various A1-LCD variants tested. Regarding the prediction of material properties for condensates of A1-LCD and its variants, Mpipi-Recharged stands out as the most reliable model. Overall, this study benchmarks a range of residue-resolution coarse-grained models for the study of the thermodynamic stability and material properties of condensates and establishes a direct link between their performance and the ranking of intermolecular interactions these models consider.

biophysics↗

bioRxiv2023

Neuron-specific RNA-sequencing reveals different regeneration mechanisms in peripheral neurons after nerve injury

Peripheral neurons are heterogeneous and functionally diverse, but all share the capability to switch to a pro-regenerative state after nerve injury. Despite the assumption that the injury response is similar among neuronal subtypes, functional recovery may differ. Understanding the distinct intrinsic regenerative properties between neurons may help to improve the quality of regeneration, prioritizing the growth of axon subpopulations to their targets. Here, we present a comparative analysis of regeneration across four key peripheral neuron populations: motoneurons, proprioceptors, cutaneous mechanoreceptors, and nociceptors. Using Cre/Ai9 mice that allow fluorescent labelling of neuronal subtypes, we found that nociceptors showed the greater regeneration after a sciatic crush, followed by motoneurons, mechanoreceptors and, finally, proprioceptors. By breeding these Cre mice with Ribotag mice, we isolated specific translatomes and defined the regenerative response of these neuronal subtypes after axotomy. Only 20% of the regulated genes were common, revealing a diverse response to injury among neurons, which was also supported by the differential influence of neurotrophins among neuron subtypes. Among differentially regulated genes, we proposed MED12 as a specific regulator of the regeneration of proprioceptors. Altogether, we demonstrate that the intrinsic regenerative capacity differs between peripheral neuron subtypes, opening the door to selectively modulate these responses.

neuroscience↗

bioRxiv2023

Excitatory neuron-specific suppression of the integrated stress response pathway contributes to autism-related phenotypes in a mouse model of fragile X syndrome

Dysregulation of protein synthesis is one of the key mechanisms underlying autism spectrum disorder (ASD). However, the role of a major pathway controlling protein synthesis, the integrated stress response (ISR), in ASD remains poorly understood. Here, we demonstrate that the main arm of the ISR, eIF2 phosphorylation (p-eIF2), is suppressed in excitatory but not inhibitory neurons in a mouse model of fragile X syndrome (FXS; Fmr1-/y). We further show that the decrease in p-eIF2 is mediated via activation of the mTORC1. Genetic reduction of p-eIF2 only in excitatory neurons is sufficient to increase general protein synthesis and cause autism-like behavior. In Fmr1-/y mice, genetic restoration of p-eIF2 solely in excitatory neurons reverses elevated protein synthesis and rescues autism-related phenotypes. Thus, we reveal a previously unknown causal relationship between excitatory neuron-specific translational control via the ISR pathway, general protein synthesis and core phenotypes reminiscent of autism in a mouse model of FXS.

neuroscience↗

bioRxiv2022

Molecular and Anatomical Characterization of Parabrachial Neurons and Their Axonal Projections

The parabrachial nucleus (PBN) is a major hub that receives sensory information from both internal and external environments. Specific populations of PBN neurons are involved in behaviors including food and water intake, pain sensation, breathing regulation, as well as learning and responding appropriately to threatening stimuli. However, it is unclear how many PBN neuron populations exist and how different behaviors may be encoded by unique signaling molecules or receptors. Here we provide a repository of data on the molecular identity, spatial location, and projection patterns on dozens of PBN neuron subclusters. Using single-cell RNA sequencing, we identified 21 subclusters of neurons in the PBN and neighboring regions. Multiplexed in situ hybridization showed many of these subclusters are localized to distinct PBN subregions. We also describe two major ascending pathways that innervate distinct brain regions by analyzing axonal projections in 21 Cre-driver lines of mice. These results are all publicly available for download and provide a foundation for further interrogation of PBN functions and connections.

neuroscience↗

bioRxiv2021

Vestibular CCK neurons drive motion-induced malaise

Travel can induce motion sickness (MS) in susceptible individuals. MS is an evolutionary conserved mechanism caused by mismatches between motion-related sensory information and past visual and motion memory, triggering a malaise accompanied by hypolocomotion, hypothermia, hypophagia and nausea. Vestibular nuclei (VN) are critical for the processing of movement input from the inner ear. Motion-induced activation of VN neurons recapitulates MS-related signs. However, the genetic identity of VN neurons mediating MS- related autonomic and aversive responses remains unknown. Here, we identify a central role of cholecystokinin (CCK)-expressing VN neurons in motion-induced malaise. Moreover, we show that CCK VN inputs onto the parabrachial nucleus activate Calca- expressing neurons and are sufficient to establish avoidance to novel food, which is prevented by CCK-A receptor antagonism. These observations provide greater insight into the neurobiological regulation of MS by identifying the neural substrates of MS and providing potential targets for treatment. SIGNIFICANCE STATEMENTWe live in an age where travel is paramount. However, one of the most disabling conditions inherent to traveling is motion sickness (MS). While studies have underscored the role of the vestibular system in the development of MS, the neuronal populations involved in motion-induced malaise remain largely unknown. Here, we describe the vestibular pathways eliciting MS responses, and identify a key role for cholecystokinin (CCK)-expressing vestibular neurons. We reveal that a vestibulo-parabrachial (PBN) CCKergic projection is sufficient to induce conditioned taste aversion, likely through the activation of calcitonin gene-related peptide-expressing PBN neurons. Finally, we underscore the role of CCK-A receptor signaling as a novel druggable target to treat MS, providing novel insight on the neurobiological substrates of MS.

neuroscience↗

bioRxiv2020

Activation of Kiss1 neurons in the preoptic hypothalamus stimulates testosterone synthesis in adult male mice

Kisspeptin-expressing neurons in the rostral periventricular region of the third ventricle (RP3V) play an essential role in female reproduction. However, adult male mice were reported to have very few Kisspeptin-expressing neurons in the RP3V compared to females. This led to the hypothesis that Kiss1RP3V neurons are responsible for the ability of females, but not males, to generate a surge of LH, triggering ovulation and steroid synthesis in the female. Using mouse genetics and cell type-specific gene expression analysis, we show that male mice harbor almost as many Kiss1RP3V neurons as the female and that gene expression in these neurons is very similar. Specific activation of male Kiss1RP3V neurons expressing viral-encoded hM3Dq caused a surge in serum testosterone levels. These results demonstrate that Kiss1RP3V neurons are present in the adult male and fully capable of regulating the hypothalamic/pituitary/gonadal axis. We suggest that these neurons may continue to play a role in reproductive behavior in adult male mice.

neuroscience↗

bioRxiv2019

Mitochondrial Proteome of Affected Neurons in a Mouse Model of Leigh Syndrome

Defects in mitochondrial function lead to severe neuromuscular orphan pathologies known as mitochondrial disease. Among them, Leigh Syndrome is the most common pediatric presentation, characterized by symmetrical brain lesions, hypotonia, motor and respiratory deficits, and premature death. Mitochondrial diseases are characterized by a marked anatomical and cellular specificity. However, the molecular determinants for this susceptibility are currently unknown, hindering the efforts to find an effective treatment. Due to the complex crosstalk between mitochondria and their supporting cell, strategies to assess the underlying alterations in affected cell types in the context of mitochondrial dysfunction are critical. Here, we developed a novel virus-based tool, the AAV-mitoTag viral vector, to isolate mitochondria from genetically-defined cell types. Administration of the AAV-mitoTag in the vestibular neurons of a mouse model of Leigh Syndrome lacking the complex I subunit Ndufs4 allowed us to assess the proteome and acetylome of susceptible neurons in a well characterized model recapitulating the human disease. Our results show a marked reduction of complex-I N-module subunit abundance and an increase in the levels of the assembly factor NDUFA2. Transiently-associated non-mitochondrial proteins such as PKC{delta}, and the complement subcomponent C1Q were also increased in Ndufs4-deficient mitochondria. Furthermore, lack of Ndufs4 induced pyruvate dehydrogenase (PDH) subunit hyperacetylation, leading to decreased PDH activity. We provide novel insight on the pathways involved in mitochondrial disease, which could underlie potential therapeutic approaches for these pathologies.

neuroscience↗

bioRxiv2019

Defined neuronal populations drive fatal phenotype in Leigh Syndrome

Dysfunctions of the mitochondrial energy-generating machinery cause a series of progressive, untreatable and usually fatal diseases collectively known as mitochondrial disease. High energy-requiring organs such as the brain are especially affected, leading to developmental delay, ataxia, respiratory failure, hypotonia, seizures and premature death. While neural affectation is a critical component of the pathology, only discrete neuronal populations are susceptible. However, their molecular identity and their contribution to the disease remain unknown. Mice lacking the mitochondrial Complex I subunit NDUFS4 (Ndufs4KO mice) recapitulate the classical signs of Leigh Syndrome (LS), the most common presentation of mitochondrial disease with predominant CNS affectation. Here, we identify the critical role of two genetically-defined neuronal populations driving the fatal phenotype in Ndufs4KO mice. Selective inactivation of Ndufs4 in Vglut2-expressing glutamatergic neurons causes brainstem inflammation, motor and respiratory deficits, and early death. On the other hand, Ndufs4 deletion in GABAergic neurons leads to basal ganglia inflammation without motor or respiratory involvement, but accompanied by severe refractory epileptic seizures preceding premature death. These results provide novel insight in the cell type-specific contribution to LS pathology and open new avenues to understand the underlying cellular mechanisms of mitochondrial disease.

neuroscience↗