Biology subjects

Lopez, S. G.

Publications and source records attributed to Lopez, S. G..

7 recordsLinked to original sources

bioRxiv2026

Transcriptomic analysis of human induced pluripotent stem cell cardiomyocytes and myocardial tissue reveals novel role for miR-9-5p in hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is an inherited disease characterized by the thickening of the heart muscle. Mutations in genes encoding contractile proteins, such MYBPC3 and MYH7 account for over half of patients with familial HCM. MicroRNAs (miRNAs) are pivotal regulators of gene expression that may influence disease progression. Despite their potential significance, there is a scarcity of published data on miRNAs in HCM. Induced pluripotent stem cells (iPSCs) have emerged as valuable tools for modeling various cardiovascular diseases, including HCM. However, the miRNA expression profiles associated with HCM remain largely unexplored within iPSC models. Investigating the differential expression of miRNAs in HCM patients offers a promising avenue to identify potential therapeutic targets for individuals affected by this condition. In this study, we performed an unbiased screen using a microarray (NanoString Technologies) that contained 798 miRNAs to identify differentially expressed miRNAs in iPSC-cardiomyocytes (CM) and myocardial tissues derived from healthy donors and HCM patients with MYBPC3 and MYH7 mutations, identifying miR-9-5p as significantly downregulated in all HCM iPSC-CM and myectomy tissue compared to control. KEGG pathway analysis of gene targets using miRTarBase and g:Profiler revealed that miR-9-5p regulates genes in the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor resistance pathway, which is involved in hypercontractility associated with HCM. Modulation of miR-9-5p expression in vitro using mimics significantly reduced cardiomyocyte size and contractility of MYBPC3 mutant iPSC-CMs whereas healthy control iPSC-CMs treated with antagomiRs exhibited hypertrophy. Our findings identify miR-9-5p as a regulator of cardiomyocyte hypertrophy and contractility, and suggest the miR-9-5p/EGFR tyrosine kinase inhibitor resistance axis as a potential therapeutic target to mitigate hypertrophy and hypercontractility exhibited in HCM.

molecular biology↗

bioRxiv2025

Starch synthesis in Brachypodium distachyon endosperm occurs in dynamic, connected amyloplast compartments

The morphology of starch granules is a major determinant of the functional and nutritional properties of starch and is highly variable among cereal species. Much of this morphological variation stems from differences in the spatial and temporal patterns of starch granule initiation in amyloplasts during grain development. Simple granules are thought to arise from a single initiation per amyloplast (e.g., in Brachypodium distachyon), whereas compound granules develop from multiple initiations per amyloplast (e.g., in rice). Using live-cell imaging in transgenic Brachypodium lines expressing a fluorescent amyloplast reporter construct, we discovered that simple-type starch granules in Brachypodium can arise from multiple initiations per amyloplast. The amyloplasts showed dynamic changes in their structure, the formation of stromules, and the movement of both the amyloplast within the cell and the starch granules within the amyloplasts. Our results suggest complex and pleiomorphic amyloplast organisation and mobility that can influence starch granule formation and morphology. This goes beyond the existing one granule, one amyloplast model for simple-type granules, and advances our understanding of both amyloplast biogenesis and granule formation.

plant biology↗

bioRxiv2025

Delayed lubricin injection improves cartilage repair tissue quality in an in vivo rabbit osteochondral defect model

Osteochondral lesions (OCL) are common among young patients and often require surgical interventions since cartilage has a poor capacity for self-repair. Bone marrow stimulation (BMS) has been used clinically for decades to treat OCLs, however a persisting challenge with BMS and other cartilage repair strategies is the inferior quality of the resulting fibrocartilaginous repair tissue. Lubrication-based therapies have the potential to improve the quality of cartilage repair tissue as joint lubrication is linked to local cartilage tissue strains and subsequent cellular responses including death and apoptosis. Recently, a full length recombinant human lubricin (rhLubricin) was developed and has been shown to lower friction in cartilage. This study investigated the effect of a single delayed injection of rhLubricin on cartilage repair in an in vivo rabbit OCL model using gross macroscopic evaluation, surface profilometry, histology, and tribology. Moderate improvement in macroscopic scores for cartilage repair were observed. Notably, quantitative analysis of Safranin-O histology showed that rhLubricin treated joints had significantly higher glycosaminoglycan content compared to saline treated joints, and there were no differences in repair integration between groups. Furthermore, rhLubricin treated joints had significantly lower friction coefficients tested across three sliding speeds compared to saline treated joints (rhLubricin: 0.15 {+/-} 0.03 at 0.1 mm/s to 0.12 {+/-} 0.03 at 10 mm/s, Saline: 0.22 {+/-} 0.06 at 0.1 mm/s to 0.19 {+/-} 0.05 at 10 mm/s). Overall, a single delayed injection of rhLubricin improved the quality and lubricating ability of the repair cartilage tissue without inhibiting repair tissue integration.

bioengineering↗

bioRxiv2024

Modular structure of RNA 3' processing condensates involving the Arabidopsis RNA binding protein FCA

Our understanding of the functional requirements underpinning biomolecular condensation in vivo is still relatively poor. The Arabidopsis RNA binding protein FCA is found in liquid-like nuclear condensates that function in transcription termination, promoting proximal polyadenylation at many targets in the Arabidopsis genome. To further understand the properties of these condensates in vivo we used single particle tracking experiments on FCA reporters stably expressed at endogenous levels in plant nuclei. These revealed FCA forms a core oligomer of [~]4 molecules that multimerizes into higher-order particles. This assembles into macromolecular condensates through the function of the coiled-coil protein FLL2, which is genetically required for FCA function. FLL2 predominately co-localizes with FCA in larger sized condensates. A missense mutation in the FCA RRM domain, also genetically required for FCA function, reduced both average FCA particle and condensate size but did not perturb the core oligomer. Our work points to a modular structure for FCA condensates involving multimerization of core oligomers that assemble into functional macromolecular condensates via associated RNA and FLL2 interactions.

molecular biology↗

bioRxiv2022

Direct measurement of appressorium turgor using a molecular mechanosensor in the rice blast fungus Magnaporthe oryzae

Many plant pathogenic fungi forcibly enter their hosts to cause disease. The rice blast fungus Magnaporthe oryzae, for example, infects plants using a specialised infection cell called an appressorium, which generates enormous turgor to drive a rigid penetration peg through the rice leaf cuticle. While these vast internal pressures are a critical weapon in fungal host penetration, they have remained very challenging to probe directly during host invasion, leaving our understanding of these extreme cellular mechanics incomplete. Here, we combine Fluorescence Lifetime Imaging (FLIM) with a membrane-targeting molecular mechanoprobe to quantify changes in membrane tension as a direct proxy for appressorial turgor in M. oryzae. We report that mature melanin-pigmented M. oryzae appressoria display a heterogeneous low fluorescence lifetime and high membrane tension, consistent with enormous turgor. These extreme pressures lead to large-scale spatial heterogeneities in membrane mechanics, much greater than observed in any other cell type previously, highlighting the extreme mechanics of turgor-driven appressorium-mediated plant infection. By contrast, appressoria of non-pathogenic melanin-deficient mutants, alb1 and buf1, or immature non-melanised appressoria, exhibit high fluorescence lifetime, consistent with low membrane tension and turgor, that remain spatially homogeneous. To evaluate the method, we investigated turgor dynamics in a range of mutants impaired in appressorium function. We show that the turgor sensor kinase mutant{Delta} sln1, recently proposed to generate excess appressorium turgor, displayed a significantly higher membrane tension compared to an isogenic wild type M. oryzae strain. This non-invasive, live cell imaging technique allows direct quantification and visualization of the enormous turgor pressures deployed during pathogen infection.

cell biology↗

bioRxiv2022

MOSQUITO MICROBIOMES OF RWANDA: CHARACTERIZING MOSQUITO HOST AND MICROBIAL COMMUNITIES IN THE LAND OF A THOUSAND HILLS

Mosquitoes are a complex nuisance around the world, and tropical countries bear the greatest brunt of the burden of mosquito-borne diseases. Rwanda has had success in reducing malaria and some arboviral diseases over the last few years, but still faces challenges to elimination. By building our understanding of in situ mosquito communities in Rwanda at a disturbed, human-occupied site and at a natural, preserved site, we can build our understanding of natural mosquito microbiomes toward the goal of implementing novel microbial control methods. Here, we examined the composition of collected mosquitoes and their microbiomes at two diverse sites using Cytochrome c Oxidase I sequencing and 16S V4 barcode sequencing. The majority of mosquitoes captured and characterized in this study are the first-known record of their species for Rwanda but have been characterized in other nations in East Africa. Beta diversity metrics were significantly different between sampling sites, mosquito genera, and mosquito species, but not between mosquito sexes, catch method, or presumed bloodfed status. Bacteria of interest for arbovirus control, Asaia, Serratia, and Wolbachia, were found in abundance at both sites, but were more prevalent at the disturbed site and varied greatly by species. Additional studies to build our understanding of naturally-formed microbial communities are essential to safely employing microbial control methods and further reducing the burden of mosquito-borne diseases.

ecology↗

bioRxiv2019

Lysosomal perturbations in dopaminergic neurons derived from induced pluripotent stem cells with PARK2 mutation

Mutations in the PARK2 gene encoding parkin, an E3 ubiquitin ligase, are associated with autosomal recessive early-onset Parkinsons disease (PD). While parkin has been implicated in the regulation of mitophagy and proteasomal degradation, the precise mechanism leading to neurodegeneration in both sporadic and familial PD upon parkin loss-of-function mutations remains unknown. Cultures of isogenic induced pluripotent stem cell (iPSC) lines with and without PARK2 knockout (KO) enable mechanistic studies of the effect of parkin deficiency in human dopaminergic neurons. In the present study, we used such cells to investigate the impact of PARK2 KO on the lysosomal compartment combining different approaches, such as mass spectrometry-based proteomics, electron microscopy (TEM) analysis and functional assays. We discovered a clear link between parkin deficiency and lysosomal alterations. PARK2 KO neurons exhibited a perturbed lysosomal morphology, displaying significantly enlarged and electron-lucent lysosomes as well as an increased total lysosomal content, which was exacerbated by mitochondrial stress. In addition, we found perturbed autophagic flux and decreased lysosomal enzyme activity suggesting an impairment of the autophagy-lysosomal pathway in parkin-deficient cells. Interestingly, activity of the GBA-encoded enzyme, {beta}-glucocerebrosidase, was significantly increased suggesting the existence of a compensatory mechanism. In conclusion, our data provide a unique characterization of the morphology, content, and function of lysosomes in PARK2 KO neurons, thus revealing a new important connection between mitochondrial dysfunction and lysosomal dysregulation in PD pathogenesis.

neuroscience↗