Biology subjects

Medina-Carbonero, M.

Publications and source records attributed to Medina-Carbonero, M..

5 recordsLinked to original sources

bioRxiv2024

SYSTEMIC FRATAXIN DEFICIENCY CAUSES TISSUE-DEPENDENT IRON HOMEOSTASIS ALTERATIONS: IMPLICATIONS FOR FRIEDREICH ATAXIA

Friedreich Ataxia (FA) is a cardio-neurodegenerative disease caused by mutations in the frataxin gene, which result in low frataxin expression. It is well-established that frataxin deficiency affects iron homeostasis, but the tissue-specificity of these alterations is poorly understood. In this study, we have analyzed iron homeostasis alterations in the FXNI151F mouse model, which presents systemic frataxin deficiency and neurological defects resembling FA patients. Iron overload is observed in the brain from 21-week old FXNI151F mice, both males and females, and it does not further accumulate in older animals. It is also observed in livers from 39-week old mutant females, but not in males. Iron signaling is altered in all tissues: in brain and liver Iron Regulatory Protein 1 (IRP1) content is decreased, while in heart increased IRP2 and decreased specific aconitase 2 activity are observed. Remarkably, these cardiac alterations are partially restored in 39- week-old animals, suggesting that the heart is activating an iron-deficiency response to compensate for deficient iron-sulfur biogenesis. Our findings demonstrate that frataxin deficiency affects iron homeostasis in a time dependent and tissue-specific manner, and that the pathological mechanisms in FA comprise both iron accumulation and limited iron availability. Understanding this specificity is crucial for the design of iron-related therapeutic interventions aiming to improve FA symptomatology.

biochemistry↗

bioRxiv2024

LiveLattice: Real-time visualization of tilted light-sheet microscopy data using a memory-efficient transformation algorithm

Light-sheet fluorescence microscopy (LSFM), a prominent fluorescence microscopy technique, offers enhanced temporal resolution for imaging biological samples in four dimensions (4D; x, y, z, time). Some of the most recent implementations, including inverted selective plane illumination microscopy (iSPIM) and lattice light-sheet microscopy (LLSM), rely on a tilting of the sample plane with respect to the light sheet of 30-45 degrees to ease sample preparation. Data from such tilted-sample-plane LSFMs require subsequent deskewing and rotation for proper visualization and analysis. Such transformations currently demand substantial memory allocation. This poses computational challenges, especially with large datasets. The consequence is long processing times compared to data acquisition times, which currently limits the ability for live-viewing the data as it is being captured by the microscope. To enable the fast preprocessing of large light-sheet microscopy datasets without significant hardware demand, we have developed WH-Transform, a novel GPU-accelerated memory-efficient algorithm that integrates deskewing and rotation into a single transformation, significantly reducing memory requirements and reducing the preprocessing run time by at least 10-fold for large image stacks. Benchmarked against conventional methods and existing software, our approach demonstrates linear scalability. Processing large 3D stacks of up to 15 GB is now possible within one minute using a single GPU with 24 GB of memory. Applied to 4D LLSM datasets of human hepatocytes, human lung organoid tissue, and human brain organoid tissue, our method outperforms alternatives, providing rapid, accurate preprocessing within seconds. Importantly, such processing speeds now allow visualization of the raw microscope data stream in real time, significantly improving the usability of LLSM in biology. In summary, this advancement holds transformative potential for light-sheet microscopy, enabling real-time, on-the-fly data processing, visualization, and analysis on standard workstations, thereby revolutionizing biological imaging applications for LLSM, SPIM and similar light microscopes.

cell biology↗

bioRxiv2023

Deficient mitochondrial respiration impairs sirtuin activity in dorsal root ganglia in Friedreich Ataxia mouse and cell models

Friedreich ataxia (FA) is a rare, recessive neuro-cardiodegenerative disease caused by deficiency of the mitochondrial protein frataxin. Mitochondrial dysfunction, a reduction in the activity of iron-sulfur enzymes, iron accumulation, and increased oxidative stress have been described. However, the mechanisms causing such cellular disturbances in mammals are not completely understood. Dorsal root ganglion (DRG) sensory neurons are among the cellular types most affected in the early stages of this disease. We have previously demonstrated that frataxin depletion in primary cultures of DRG neurons results in calcium dysregulation, neurite degeneration and apoptotic cell death. However, its effect on mitochondrial function remains to be elucidated. In the present study, we found that in primary cultures of DRG neurons as well as in DRGs from the FXNI151F mouse model, frataxin deficiency resulted in lower activity and levels of the electron transport complexes, mainly complexes I and II. As a consequence, the NAD+/NADH ratio was reduced and SirT3, a mitochondrial NAD+-dependent deacetylase, was impaired. We identified alpha tubulin as the major acetylated protein from DRG homogenates whose levels were increased in FXNI151F mice compared to WT mice. Mitochondrial superoxide dismutase (SOD2), a SirT3 substrate, displayed increased acetylation in frataxin-deficient DRG neurons. Since SOD2 acetylation inactivates the enzyme, and higher levels of mitochondrial superoxide anion were detected, oxidative stress markers were analyzed. Elevated levels of hydroxynonenal bound to proteins and mitochondrial Fe2+ accumulation were detected when frataxin decreased. Honokiol, a SirT3 activator, restores mitochondrial respiration. Altogether, these results provide the molecular bases to understand mitochondria dysfunction in sensory neurons which have greater susceptibility to frataxin deficiency compared to other tissues.

neuroscience↗

bioRxiv2021

Biochemical alterations precede neurobehavioral deficits in a novel mouse model of Friedreich ataxia

Friedreich Ataxia (FA) is a rare neuro-cardiodegenerative disease, caused by partial deficiency of frataxin, a mitochondrial protein. This deficiency is caused by the presence of a GAA triplet expansion in the first intron of the frataxin gene or, in some patients, by point mutations. Generating mouse models mimicking FA has been challenging, as this disease is manifested when frataxin levels are below a pathological threshold. In the present work, we have characterized a new mouse model of FA (FXNI151F) based on a pathological point mutation (I154F) present in some FA patients. These mice present very low frataxin levels in all tissues and display neurological deficits resembling those observed in FA patients. We have also observed decreased content of components from OXPHOS complexes I and II, decreased aconitase activity, and alterations in the antioxidant defenses. Remarkably, these biochemical alterations precede the appearance of neurological symptoms and present a different profile in heart and brain or cerebellum. The FXNI151F mouse is an excellent tool for analyzing the consequences of frataxin deficiency in different tissues and for testing new therapies.

biochemistry↗

bioRxiv2020

Calcitriol increases frataxin levels and restores altered markers in cell models of Friedreich Ataxia

Friedreich Ataxia (FA) is a neurodegenerative disease caused by the deficiency of frataxin, a mitochondrial protein. In primary cultures of dorsal root ganglia neurons, we showed that frataxin depletion resulted in decreased levels of the mitochondrial calcium exchanger NCLX, neurite degeneration and apoptotic cell death. Here we describe that frataxin-deficient dorsal root ganglia neurons display low levels of ferredoxin 1, a mitochondrial Fe/S cluster-containing protein that interacts with frataxin and, interestingly, is essential for the synthesis of calcitriol, the active form of vitamin D. We provide data that calcitriol supplementation, used at nanomolar concentrations, is able to reverse the molecular and cellular markers altered in DRG neurons. Calcitriol is able to recover both ferredoxin 1 and NCLX levels and restores mitochondrial membrane potential. Accordingly, apoptotic markers and neurite degeneration are reduced resulting in cell survival recovery with calcitriol supplementation. All these beneficial effects would be explained by the finding that calcitriol is able to increase the mature frataxin levels in both, frataxin-deficient DRG neurons and cardiomyocytes; remarkably, this increase also occurs in lymphoblastoid cell lines derived from FA patients. In conclusion, these results provide molecular bases to consider calcitriol for an easy and affordable therapeutic approach for FA patients.

biochemistry↗