Biology subjects

Luna, G.

Publications and source records attributed to Luna, G..

8 recordsLinked to original sources

bioRxiv2025

How much can reticulate evolution entangle plant systematics? Revisiting subfamilial classification of the Malvatheca clade (Malvaceae) on the basis of phylogenomics

Reticulate evolution (RE), involving hybridization and related processes, generates network-like rather than strictly bifurcating relationships among lineages and can obscure phylogenetic relationships. Detecting ancient hybridization is particularly challenging, as genomic signals may erode over time. The Malvatheca clade (Malvaceae), marked by multiple paleopolyploidy events since its estimated origin 66 my, offers a useful model for examining RE. Its three subfamilies--Bombacoideae (with high chromosome numbers, mostly trees), Malvoideae (lower chromosome numbers, mostly herbs), and the recently described Matisioideae--show unresolved relationships, with several taxa of uncertain placement. We conducted a phylogenomic analysis of 62 Malvatheca species via complete plastomes, 35S rDNA cistrons, and comparative repeatome data. All datasets consistently resolved three main clades: (i) Bombacoideae, (ii) Malvoideae, and (iii) a heterogeneous assemblage including most of the recently assigned Matisioideae and several incertae sedis taxa, suggesting a more complex evolutionary history and circumscription than previously recognized. Chromosome numbers were negatively correlated with repeatome diversity: Bombacoideae presented higher counts but lower repeat diversity, possibly reflecting slower repeat evolution associated with woody growth forms. In contrast, clade III showed marked heterogeneity in both chromosome number and repeat composition, which is consistent with a reticulate origin. Overall, our results show evidence of ancient hybridization and polyploidy, predominantly allopolyploidy, in shaping Malvatheca evolution. These results highlight that reticulation and genome dynamics, rather than taxonomic boundaries alone, are central to understanding the diversification of Malvatheca.

genomics↗

bioRxiv2025

MYRF is Essential in Mesothelial Cells to Promote Lung Development and Maturation

The mesothelium is a squamous monolayer that ensheathes internal organs, lines the body cavity, and the diaphragm. It serves as a protective barrier, coated in glycocalyx, and secretes lubricants to facilitate tissue movement. How the mesothelium forms is poorly understood. Here, we investigate Myrf, a transcription factor gene expressed in the mesothelium, because it carries variants in patients with Congenital Diaphragmatic Hernia (CDH), a disorder that affects the diaphragm, lung, and other organs. In mice, inactivation of Myrf early in organogenesis resulted in CDH and defective mesothelial specification, compromising its function as a signaling center for lung growth. Inactivation of Myrf later led to enhanced mesothelium differentiation into mesenchymal cell types through partial epithelial-to-mesenchymal transition (EMT), resulting in a unique accumulation of smooth muscle encasing the lung. In this role, MYRF functions in parallel with YAP/TAZ. Together, these findings establish MYRF as a critical regulator of mesothelium development, and when mutated, causes CDH.

developmental biology↗

bioRxiv2024

Effects of HA1 (a Probucol Analogue) and ApoC3 siRNA on Lipoprotein-Amyloid Metabolism, Neurovascular Integrity and Cognitive Function in db/db Mice

Background and aimsChronically elevated levels of circulating lipoprotein-amyloid-{beta} (A{beta}) are implicated in the disruption of the blood-brain barrier and the initiation of a neurodegenerative cascade leading to Alzheimers disease (AD). Type 2 diabetes is associated with BBB dysfunction, dyslipidaemia, and an increased risk of AD. However, alterations in triglyceride-rich lipoproteins (TRL)-A{beta} homeostasis and its downstream effects on the BBB in a diabetes context remain explored. This study aimed to 1) investigate, in a preclinical model of diabetes, the hypothesis that diabetes-induced impairments in TRL-A{beta} metabolism might compromise BBB integrity and exacerbate cognitive function and behavioural changes, and 2) assess the efficacy of interventions that improve TRL catabolism, including probucol, HA1, and ApoC3 siRNA, to prevent disease progression by lowering circulating TRL-A{beta} levels. MethodsFive-week-old db/db mice underwent a 9- or 23-weeks dietary interventions with probucol, a probucol prodrug HA1, or a standard diet with four-weekly injections of ApoC3 siRNA. Db/+ mice served as negative controls for each treatment duration. Blood levels of A{beta} and ApoB were measured using ELISA. Immunofluorescence imaging was used to quantify enterocytic levels of A{beta} and ApoB, and assess changes in neurovascular integrity (IgG, PDGFR{beta}, ZO1, occludin), neuroinflammation (GFAP, Iba1), and cerebral oxidative stress (8OHdG). ResultsOur results indicate that diabetes increased the abundance of plasma amyloid, specifically A{beta}42, which correlated with enterocytic abundance, suggesting exaggerated postprandial excretion. Disrupted plasma amyloid homeostasis was associated with BBB breakdown, including diminished barrier function, and the loss of pericytes and astrocytes. Provision of the probucol analogue, HA1, normalised plasma and enterocytic amyloidemia concomitant with the preservation of the neurovascular junction. Treatment with ApoC3 siRNA attenuated plasma A{beta}42 and modestly reduced neurovascular inflammation. ConclusionThe findings further support the hypothesis that aberrant peripheral metabolism of lipoprotein-A{beta} is associated with microvascular corruption and the development of anxiety-like behaviour. HA1 is more effective than probucol or ApoC3 siRNA in positively modulating lipoprotein-amyloid homeostasis in db/db mice and maintaining central capillary integrity. HighlightsO_LIEnterocytic and plasma lipoprotein-A{beta} levels are increased in diabetic db/db mice. C_LIO_LIElevated plasma lipoprotein-A{beta} levels correlate with BBB breakdown and anxiety-like behavior. C_LIO_LIHA1 lowers enterocytic and plasma A{beta} levels, protects BBB, alleviates oxidative stress and anxiety. C_LIO_LIApoC3 siRNA lowers plasma lipoprotein-A{beta}, mitigates neuroinflammation and anxiety. C_LI

neuroscience↗

bioRxiv2021

Long-term Transverse Imaging of the Hippocampus with Glass Microperiscopes

The hippocampus consists of a stereotyped neuronal circuit repeated along the septal-temporal axis. This transverse circuit contains distinct subfields with stereotyped connectivity that support crucial cognitive processes, including episodic and spatial memory. However, comprehensive measurements across the transverse hippocampal circuit in vivo are intractable with existing techniques. Here, we developed an approach for two-photon imaging of the transverse hippocampal plane in awake mice via implanted glass microperiscopes, allowing optical access to the major hippocampal subfields and to the dendritic arbor of pyramidal neurons. Using this approach, we tracked dendritic morphological dynamics on CA1 apical dendrites and characterized spine turnover. We then used calcium imaging to quantify the prevalence of place and speed cells across subfields. Finally, we measured the anatomical distribution of spatial information, finding a non-uniform distribution of spatial selectivity along the DG-to-CA1 axis. This approach extends the existing toolbox for structural and functional measurements of hippocampal circuitry.

neuroscience↗

bioRxiv2021

Intrinsic network activity in human brain organoids

Human brain organoids replicate much of the cellular diversity and developmental anatomy of the human brain. However, the physiological behavior of neuronal circuits within organoids remains relatively under-explored. With high-density CMOS microelectrode arrays (26,400 electrodes) and shank electrodes (960 electrodes), we probed broadband and three-dimensional extracellular field recordings generated by spontaneous activity of human brain organoids. These recordings simultaneously captured local field potentials (LFPs) and single-unit activity extracted through spike sorting. From spiking activity, we estimated a directed functional connectivity graph of synchronous neural network activity, which showed a large number of weak functional connections enmeshed within a network skeleton of significantly fewer strong connections. Treatment of the organoid with a benzodiazepine induced a reproducible signature response that shortened the inter-burst intervals, increased the uniformity of the firing pattern within each burst and decreased the population of weakly connected edges. Simultaneously examining the spontaneous LFPs and their phase alignment to spiking showed that spike bursts were coherent with theta oscillations in the LFPs. Our results demonstrate that human brain organoids have self-organized neuronal assemblies of sufficient size, cellular orientation, and functional connectivity to co-activate and generate field potentials from their collective transmembrane currents that phase-lock to spiking activity. These results point to the potential of brain organoids for the study of neuropsychiatric diseases, drug mechanisms, and the effects of external stimuli upon neuronal networks.

neuroscience↗

bioRxiv2019

Cell population effects in a mouse tauopathy model identified by single cell sequencing

Neurodegenerative disorders are complex multifactorial diseases that have poorly understood selective vulnerabilities among discrete cell populations. We performed single cell RNA sequencing of whole hippocampi from the rTg4510 mouse tauopathy model, which expresses a P301L MAPT mutation at two time points--before and after the onset of pathology. One population of neurons showed a robust size reduction in both the young and the old transgenic animals. Differential expression of genes expressed in this group of neurons suggested an enrichment in granule cell neurons. We identified genes that characterize this population of neurons using Pareto optimization of the specificity and precision of gene pairs for the population of interest. The resulting optimal marker genes were overwhelmingly associated with neuronal projections and their expression was enriched in the dentate gyrus suggesting that the rTg4510 mouse is a good model for Picks disease. This observation suggested that the tau mutation affects the population of neurons associated with neuronal projections even before overt tau inclusions can be observed. Out of the optimal pairs of genes identified as markers of the population of neurons of interest, we selected Purkinje cell protein 4 (Pcp4+) and Syntaxin binding protein 6 (Stxbp6+) for experimental validation. Single-molecule RNA fluorescence in situ hybridization confirmed preferential expression of these markers and localized them to the dentate gyrus.

cell biology↗

bioRxiv2019

Single-cell chromatin accessibility analysis of mammary gland development reveals cell state transcriptional regulators and cellular lineage relationships

It has only recently become possible to obtain single-cell level resolution of the epigenetic changes that occur during organ development. We reasoned that precision single-cell chromatin accessibility mapping of mammary gland development could provide needed insight into the epigenetic reprogramming and transcriptional regulators involved in normal mammary gland development. Here, we provide the first single-cell resource of chromatin accessibility for murine mammary development from the peak of fetal mammary stem cell (fMaSC) functional activity in late embryogenesis to the differentiation of adult basal and luminal cells. We find that the chromatin landscape within individual cells predicts both gene accessibility and transcription factor activity, and we present a web application as a scientific resource for facilitating future analyses. Strikingly, these single-cell chromatin profiling data reveal that fMaSCs can be separated into basal-like and luminal-like lineages, providing evidence of early lineage segregation prior to birth. Such distinctions were not evident in analyses of single-cell transcriptomic data.

genomics↗

bioRxiv2018

Farnesyl Transferase Inhibition for the Treatment of Tauopathies

Tau inclusions are a shared feature of many neurodegenerative conditions and tau mutations lead to frontotemporal dementia. Approaches to treatment of these conditions have focused directly on the tau protein by targeting its post-translational modifications, its levels and its tendency to aggregate. We discovered a novel regulatory pathway for tau degradation that operates through the Rhes protein, a GTPase. Rhes is farnesylated and treatment with the farnesyl transferase inhibitor, lonafarnib, reduced Rhes, attenuated behavioral abnormalities, significantly reduced atrophy, tau inclusions, sumoylation and ubiquitination, as well as microgliosis in the rTg4510 tauopathy mouse. Direct reduction of Rhes levels reproduced the results observed with lonafarnib. The mechanism of lonafarnib action, as mediated by Rhes to reduce tau pathology, operates through the lysosome without involvement of the proteasome. Finally we show that the developmental increase in Rhes levels can be homeostatically regulated in the presence of tau mutations as a protective mechanism through which cells sense abnormal tau before any pathology is present. The extensive human trials of lonafarnib for other conditions, makes this drug ideal for repurposing to treat tauopathies.\n\nOne-sentence summaryVia a mechanism that involves targeting Rhes, lonafarnib can induce lysosomal-mediated tau degradation and prevent pathology in a tau mouse model

neuroscience↗