Biology subjects

Martin-Lopez, E.

Publications and source records attributed to Martin-Lopez, E..

6 recordsLinked to original sources

bioRxiv2025

Rapid quantification of short-chain fatty acids by Fourier-transform infrared spectroscopy for microbiota quality assessment

Short-chain fatty acids (SCFAs) are bacterial metabolites with crucial roles in host homeostasis and immune system modulation. Given their benefits, they have been proposed as markers of a healthy microbiota. Their quantification, however, is time-consuming, expensive and requires specialized personal and equipment. Thus, their use for quality assessment of stool samples in clinical contexts is limited. In this study we explored the use of Fourier-transform infrared (FT-IR) spectroscopy as an alternative method for metabolomic quality assessment of stool samples. FT-IR identifies the chemical bonds present in SCFAs and allows clear discrimination between healthy and dysbiotic stool samples (caused by Clostridioides difficile infection) through Principal Component Analysis (PCA). Overall, FT-IR provides a rapid, cost-effective and simple method for stool samples quality assessment. Combined with the widespread availability of this technology in most hospitals, these advantages highlight its potential application for routine implementation in clinical laboratories.

microbiology↗

bioRxiv2024

Embryonically generated interneurons (EGINs) exhibit a distinctive developmental program and lamination in the olfactory bulb

Interneurons (INs) in the mouse olfactory bulb (OB) develop during an extensive period of time that begins in the embryo and continues throughout the lifetime of an individual. The connectivity and location of these neurons is profoundly affected by the time of generation, making these developmental windows critical to understand the circuitry of the OB. Here, we focus on the OB embryonic generated interneurons (or EGINs), which have generally received less attention than those generated in the adult. Birthdates of EGINs were differentiated by embryonic injections of thymidine analogs and their final destinations and phenotypes analyzed by immunohistochemistry. We found that EGINs were retained in the adult and were distributed across all layers of the OB. However, a lateral-to-medial neurogenic gradient is seen only in the earliest generated EGINs. Within the granule cell layer (GCL), EGINs predominantly accumulated in the superficial region at almost all ages and remained there during adulthood. Immunostaining for calbindin, parvalbumin, tyrosine hydroxylase, and calretinin were largely negative suggesting that EGINs may represent subpopulations of OB INs that are not yet fully characterized. Using in utero electroporation to label EGIN progenitors, we demonstrated that they reach the primordial OB as early as E13 and begin to differentiate apical dendrites by E15. At E16, EGIN progenitors clustered into a chain of migrating neuroblasts denoting the embryonic rostral migratory stream (RMS). Collectively, our data highlight the importance of studying OB INs in isolated time windows to better understand the formation of circuits that define the olfactory responses.

neuroscience↗

bioRxiv2024

Timing Matters: Lessons from Perinatal Neurogenesis in the Olfactory Bulb

In the olfactory bulb odorant receptor specific input converges into glomeruli. Deep to the glomeruli coding of odor information is tuned by local synaptic circuits. Deciphering the dendritic organization of granule cells relative to the secondary dendrites of projection neurons is a pivotal for understanding odor processing. We carried out a detailed interrogation of the granule cells including the timing of neurogenesis, laminar distribution and synaptogenesis between granule cells and projection neurons. In brief, the granule cells develop following a outside in maturation pattern from embryogenesis to adulthood following a developmental continuum. Granule cells born one week after birth exhibit a unique sublayer specific distribution pattern, marking a transition between embryonic or neonatal and adult stages. Integration into reciprocal synaptic circuits occurred 10 days post neurogenesis, We conclude that timing of neurogenesis dictates the anatomical configuration of granule cells within the olfactory bulb, which in turn regulates a preferential synaptic integration with either mitral cell or tufted cell secondary dendrites. Summary StatementThe integration and distribution of granule cells into the olfactory bulb is determined by the timing of neurogenesis. Location of somata shifts from superficial to deep during development.

neuroscience↗

bioRxiv2024

Dissecting Reactive Astrocyte Responses: Lineage Tracing and Morphology-based Clustering

O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=106 SRC="FIGDIR/small/587565v1_ufig1.gif" ALT="Figure 1"> View larger version (26K): org.highwire.dtl.DTLVardef@1899db6org.highwire.dtl.DTLVardef@1d152fcorg.highwire.dtl.DTLVardef@19f4754org.highwire.dtl.DTLVardef@3f853_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical AbstractC_FLOATNO C_FIG Brain damage triggers diverse cellular and molecular events, with astrocytes playing a crucial role in activating local neuroprotective and reparative signaling within damaged neuronal circuits. Here, we investigated reactive astrocytes using a multidimensional approach to categorize their responses into different subtypes based on morphology using the StarTrack lineage tracer, single-cell imaging reconstruction and multivariate data analysis. Our findings revealed three profiles of reactive astrocyte responses affecting cell size- and shape-related morphological parameters: "moderate," "strong," and "very strong". We also explored the heterogeneity in astrocyte reactivity, with a particular emphasis in the spatial and clonal distribution. Our research highlights the importance of the relationships between the different astrocyte subpopulations with their reactive responses, showing an enrichment of protoplasmic and fibrous astrocytes within the "strong" and "very strong" subtypes. Overall, our study contributes to a better understanding of astrocyte heterogeneity in response to an injury. By elucidating the diverse reactive responses among astrocyte subpopulations, we pave the way for future research aimed at uncovering novel therapeutic targets for mitigating the effects of brain damage and promoting neural repair.

neuroscience↗

bioRxiv2022

Alpha-synuclein pathology and reduced neurogenesis in the olfactory system affect olfaction in a mouse model of Parkinsons disease

Parkinsons Disease (PD) is characterized by multiple symptoms including olfactory dysfunction, whose underlying mechanisms remain unclear. Here, we explored pathological changes in the olfactory pathway of transgenic (Tg) mice expressing the human A30P mutant -synuclein (-syn) (-syn-Tg mice) at 6-7 and 12-14 months of age, representing early and late-stages of motor progression, respectively. -Syn-Tg mice at late stages exhibited olfactory behavioral deficits, which correlated with severe -syn pathology in projection neurons of the olfactory pathway. In parallel, olfactory bulb (OB) neurogenesis in -syn-Tg mice was reduced in the OB granule cells at 6-7 months, and OB periglomerular cells at 12-14 months, respectively, both of which could contribute to olfactory dysfunction. Proteomic analyses showed a disruption in endo- and exocytic pathways in the OB during the early stages which appeared exacerbated at the synaptic terminals when the mice developed olfactory deficits at 12-14 months. Our data suggest that, 1) the -syn-Tg mice recapitulate the olfactory functional deficits seen in PD; 2) olfactory structures exhibit spatiotemporal disparities for vulnerability to -syn pathology; 3) -syn pathology is restricted to projection neurons in the olfactory pathway; 4) neurogenesis in adult -syn-Tg mice is reduced in the OB; and 5) synaptic endo- and exocytosis defects in the OB may further explain olfactory deficits.

neuroscience↗

bioRxiv2022

Microglia maintain homeostatic conditions in the developing rostral migratory stream.

Microglia invade the neuroblast migratory corridor of the rostral migratory stream (RMS) early in development. This work examines how microglia maintain the homeostatic conditions permissive to neuroblast migration in the RMS during the early postnatal period. GFP labeled microglia in CX3CR-1GFP/+ mice assemble primarily along the outer borders of the RMS during the first postnatal week, where they exhibit predominantly an ameboid morphology and associate with migrating neuroblasts. Microglia ablation for 3 days postnatally does not impact the density of pulse labeled BrdU+ neuroblasts nor the distance migrated by tdTomato electroporated neuroblasts in the RMS. However, microglia wrap DsRed-labeled neuroblasts in the RMS of P7 CX3CR-1GFP/+;DCXDsRed/+ mice and express the phagocytic markers CD68, CLEC7A and MERTK, suggesting active phagocytosis of neuroblasts in the developing RMS. Microglia depletion for 14 days postnatally further induced an accumulation of DCX+ neuroblasts and CC3+ apoptotic cells in the RMS, a wider RMS and extended patency of the lateral ventricle extension in the olfactory bulb. These findings illustrate the importance of microglia phagocytosis in maintaining the homeostasis of the early postnatal RMS. SIGNIFICANCE STATEMENTMicroglia are brain-resident immune cells responsible for both maintaining homeostatic conditions necessary for normal neurodevelopment as well as orchestrating the brains response to environmental insults. The effects of microglia-mediated immune response during development may be of special relevance to the olfactory system, which is unique in both its vulnerability to environmental insults as well as its extended period of neurogenesis and neuronal migration. The work presented here examines how microglia maintain homeostatic conditions in the neuroblast migratory corridor of the rostral migratory stream (RMS) in the olfactory system during early postnatal development. Our findings illustrate the importance of microglia phagocytosis in the early postnatal RMS and provides insights into microglia function during periods of neurogenesis and neuronal migration.

neuroscience↗