Biology subjects

Sridharan, A.

Publications and source records attributed to Sridharan, A..

8 recordsLinked to original sources

bioRxiv2024

PBAE-PEG based lipid nanoparticles for lung cell-specific gene delivery

Delivery of modified mRNA encapsulated in lipid nanoparticles, exemplified by their successful use in COVID-19 vaccination, provides a framework for treating various genetic and acquired disorders. Herein, we developed PEGylated(PBAE-PEG) and non-PEGylated(PBAE) PBAE with lipids 4A3-SC8/DOPE/cholesterol/DOTAP to form lipid nanoparticles (LNPs) for mRNA delivery into different types of pulmonary cells in vivo. PBAE-PEG/LNP were highly active in transfecting HEK293T cells and air-liquid interfaced H441 cells in vitro. PBAE-PEG/LNP were used to express Cre-recombinase after administration to mice by intravenous injection, resulting in high transfection levels in pulmonary vascular endothelial cells. Intratracheal injection of both PBAE-PEG/LNP and PBAE/LNPs resulted in efficient and selective transfection of lung epithelial cells, identified by the expression of stabilized Cre-recombinase mRNA in club cells and alveolar type 2 cells. PBAE-PEG/LNP were most effective in transfecting alveolar type 2 cells after intratracheal injection, while PBAE/LNPs administered intratracheally were more effective in transfecting secretory airway cells. Cre-mediated recombination was specific to lung epithelial cells after intratracheal administration. Likewise, intravenous administration resulted in selective transfection of endothelial cells but not other pulmonary cell types, indicating their failure to cross the pulmonary endothelial-to-epithelial barrier. Moreover, 5-methoxyuridine modified mRNA was more efficient than unmodified mRNA in vivo but not in vitro.

bioengineering↗

bioRxiv2024

Decoding the Dewlap: Multiple signals in females and males of a gliding lizard

Social interactions across taxa are often mediated through multiple signals. Studies examining the maintenance of multiple signals are mostly focused on males and often fail to capture female signalling diversity and strategies. In the recent decade, there has been a surge in the documentation of female signalling, however, our understanding of the functional relevance of multiple signals in females still lags behind. In this study, we examined multiple signals in females of an arboreal gliding lizard, Draco dussumieri, and compared them to those in males. We specifically tested the relative role of the backup signal and the multiple receiver hypotheses in the maintenance of multiple signals in both sexes. Female D.dussumieri used a variety of signals to socially interact with conspecifics, especially using their dewlap. The signalling repertoire of females was as diverse as that of males, although the relative use of the signals varied. In females, a few signals seem to be maintained by the backup signal hypothesis, with limited support for the multiple receiver hypothesis as well. For males too, both mechanisms appeared to maintain multiple signals. Interestingly, for some signals, the sexes differed in the context in which they used a given signal. Overall, these findings highlight the functional role of multiple signals in females, which can differ from that observed in males. Therefore, traits conventionally considered male-exclusive when also examined in females can provide finer insights into trait function and evolution.

animal behavior and cognition↗

bioRxiv2024

Viral delivery of an RNA-guided genome editor for transgene-free plant germline editing

AbstractGenome editing is transforming plant biology by enabling precise DNA modifications. However, delivery of editing systems into plants remains challenging, often requiring slow, genotype-specific methods such as tissue culture or transformation. Plant viruses, which naturally infect and spread to most tissues, present a promising delivery system for editing reagents. But most viruses have limited cargo capacities, restricting their ability to carry large CRISPR-Cas systems. Here, we engineered tobacco rattle virus (TRV) to carry the compact RNA-guided TnpB enzyme ISYmu1 and its guide RNA. This innovation allowed transgene-free editing of Arabidopsis thaliana in a single step, with edits inherited in the subsequent generation. By overcoming traditional reagent delivery barriers, this approach offers a novel platform for genome editing, which can greatly accelerate plant biotechnology and basic research.

plant biology↗

bioRxiv2024

Life stage impact on the human skin ecosystem: lipids and the microbial community

While research into gut-microbe interactions is common and advanced, with multiple defined impacts on human health, studies exploring the significance of skin-microbe interactions remain underrepresented. Skin is the largest human organ, has a vast surface area, and is inhabited by a plethora of microorganisms which metabolise sebaceous lipids. Sebaceous free fatty acids are metabolized into bioactive lipid mediators with immune-modulatory properties by skin-resident microbes, including Malassezia. Intriguingly, many of the same lipid mediators are also found on human skin, implying these compounds may have microbial or mixed microbial/human origin. To support this hypothesis, we isolated lipids and microbial DNA from the skin of prepubescent, adult, pre- and post-menopausal volunteers and performed correlational analyses using skin lipidomics and metagenomics to compare lipid mediator profiles and microbiome compositions on skin with either low or high sebaceous gland activity. We found that specific microbial taxonomies were positively and negatively correlated with skin lipid mediator species with high statistical significance. 2D in vitro co-cultures with Malassezia and keratinocytes also directly linked the production of specific lipid mediators, detected on healthy human skin, to secretion of immuno-stimulatory cytokines. Together, these findings further support the hypothesis that microbial-derived skin lipid mediators influence healthy skin homeostasis and skin disease development and progression, thereby spotlighting the relevance of the skin microbiomes footprint on human health.

microbiology↗

bioRxiv2023

PRDM3/16 Regulate Chromatin Accessibility Required for NKX2-1 Mediated Alveolar Epithelial Differentiation and Function

Differential chromatin accessibility accompanies and mediates transcriptional control of diverse cell fates and their differentiation during embryogenesis. While the critical role of NKX2-1 and its transcriptional targets in lung morphogenesis and pulmonary epithelial cell differentiation is increasingly known, mechanisms by which chromatin accessibility alters the epigenetic landscape and how NKX2-1 interacts with other co-activators required for alveolar epithelial cell differentiation and function are not well understood. Here, we demonstrate that the paired domain zinc finger transcriptional regulators PRDM3 and PRDM16 regulate chromatin accessibility to mediate cell differentiation decisions during lung morphogenesis. Combined deletion of Prdm3 and Prdm16 in early lung endoderm caused perinatal lethality due to respiratory failure from loss of AT2 cell function. Prdm3/16 deletion led to the accumulation of partially differentiated AT1 cells and loss of AT2 cells. Combination of single cell RNA-seq, bulk ATAC-seq, and CUT&RUN demonstrated that PRDM3 and PRDM16 enhanced chromatin accessibility at NKX2-1 transcriptional targets in peripheral epithelial cells, all three factors binding together at a multitude of cell-type specific cis-active DNA elements. Network analysis demonstrated that PRDM3/16 regulated genes critical for perinatal AT2 cell differentiation, surfactant homeostasis, and innate host defense. Lineage specific deletion of PRDM3/16 in AT2 cells led to lineage infidelity, with PRDM3/16 null cells acquiring partial AT1 fate. Together, these data demonstrate that NKX2-1-dependent regulation of alveolar epithelial cell differentiation is mediated by epigenomic modulation via PRDM3/16. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=130 HEIGHT=200 SRC="FIGDIR/small/570481v1_ufig1.gif" ALT="Figure 1"> View larger version (27K): org.highwire.dtl.DTLVardef@500f6org.highwire.dtl.DTLVardef@821daaorg.highwire.dtl.DTLVardef@69ba87org.highwire.dtl.DTLVardef@154f754_HPS_FORMAT_FIGEXP M_FIG C_FIG Model of the role of PRMD3/16 in alveolar developmentPRMD3/16 participate in cell fate specification in the lung by modulating chromatin accessibility (top row) and by partnering with NKX2-1 and partner transcription factors to drive gene expression (second row) via a gene regulatory network required for terminal cell differentiation and surfactant expression in AT2 cells (third row). Loss of PRDM3/16 activity in lung endoderm leads to reduced AT2 quorum, failure of AT2 surfactant function, and transition to an immature AT1 phenotype (bottom panel).

developmental biology↗

bioRxiv2023

Dance or disappear: Strategic sexual signalling in Peninsular rock agama

Sexual signalling has largely been studied in the context of indirect competition among males through displays and mate choice by females. Historically, sexual signalling in females was expected to be of limited consequence. However, there is growing evidence of sexual signalling in females and its value in the context of sexual selection. Here, we test how females strategize the use of sexual signals in a socially polygynous lizard, Psammophilus dorsalis. We evaluated key hypotheses for how females should modulate their signalling, including male quality and mate availability. We simulate male quality using artificial male models to individually tagged, and intensely monitored wild female lizards, measuring their strategic investment in sexual signalling. We found that females invest more in signalling towards high quality males and increased their investment towards the later part of the only breeding season. Contrary to what is typically expected in a polygynous mating system, females not only invest in costly and elaborate sexual signals, they also modulate their usage to maximise their benefits and minimise their costs. Even in polygynous mating systems, dispersed distribution of individuals can result in females experiencing limitation in mate availability, resulting in costly sexual signalling.

ecology↗

bioRxiv2022

Iron Chelation Improves Ineffective Erythropoiesis and Iron Overload in Myelodysplastic Syndrome Mice

Myelodysplastic syndrome (MDS) is a heterogeneous group of bone marrow stem cell disorders characterized by ineffective hematopoiesis and cytopenias, most commonly anemia. Red cell transfusion therapy for anemia in MDS results in iron overload, correlating with reduced overall survival. Whether treatment of iron overload benefits MDS patients remains controversial. We evaluate underlying iron-related pathophysiology and the effect of iron chelation using deferiprone on erythropoiesis in NUP98-HOXD13 transgenic mice, a highly penetrant well-established MDS mouse model. Our results characterize an iron overload phenotype with aberrant erythropoiesis in these mice which was reversed by deferiprone-treatment. Serum erythropoietin level decreased while erythroblast erythropoietin receptor expression increased in deferiprone-treated MDS mice. We demonstrate, for the first time, normalized expression of the iron chaperones Pcbp1 and Nco4 and increased ferritin stores in late stage erythroblasts from deferiprone-treated MDS mice, evidence of aberrant iron trafficking in MDS erythroblasts. Importantly, erythroblast ferritin is increased in response to deferiprone, correlating with decreased erythroblast ROS. Finally, we confirmed increased expression of genes involved in iron uptake, sensing, and trafficking in stem and progenitor cells from MDS patients. Taken together, our findings provide evidence that erythroblast-specific iron metabolism is a novel potential therapeutic target to reverse ineffective erythropoiesis in MDS. BRIEF SUMMARYIneffective erythropoiesis in MDS mice correlates with aberrant iron trafficking within bone marrow erythroblasts, consistent with findings in MDS patient progenitors, reversed after iron chelation.

pathology↗

bioRxiv2019

Optogenetic Modulation of Cortical Neurons Using Organic Light Emitting Diodes (OLEDs)

ObjectiveThere is a need for low power, scalable photoelectronic devices and systems for emerging optogenetic needs in neuromodulation. Conventional light emitting diodes (LEDs) are constrained by power and lead-counts necessary for scalability. Organic LEDs (OLEDs) offer an exciting approach to decrease power and lead-counts while achieving high channel counts on thin, flexible substrates that conform to brain surfaces or peripheral neuronal fibers. In this study, we investigate the potential for using OLEDs to modulate neuronal networks cultured in vitro on a transparent microelectrode array (MEA) and subsequently validate neurostimulation in vivo in a transgenic mouse model.\n\nApproachCultured mouse cortical neurons were transfected with light-sensitive opsins such as blue-light sensitive channel-rhodopsin (ChR2) and green-light sensitive chimeric channel-rhodopsin (C1V1tt) and stimulated using blue and green OLEDs (with 455 and 520 nm peak emission spectra respectively) at a power of 1 mW/mm2 under pulsed conditions.\n\nMain resultsWe demonstrate neuromodulation and optostimulus-locked, single unit-neuronal activity in neurons expressing stimulating and inhibiting opsins (n=4 MEAs, each with 16 recordable channels). We also validated the optostimulus-locked response in a channel-rhodopsin expressing transgenic mouse model, where at least three isolatable single neuronal cortical units respond to OLED stimulation.\n\nSignificanceThe above results indicate the feasibility of generating sufficient luminance from OLEDs to perform neuromodulation both in vitro and in vivo. This opens up the possibility of developing thin, flexible OLED films with multiple stimulation sites that can conform to the shape of the neuronal targets in the brain or the peripheral nervous system. However, stability of these OLEDs under chronic conditions still needs to be carefully assessed with appropriate packaging approaches.

bioengineering↗