Biology subjects

Mruk, K.

Publications and source records attributed to Mruk, K..

7 recordsLinked to original sources

bioRxiv2026

Arsenic Impairs Critical Cellular Events of Human Cardiac Development Across Differentiation and Metabolic Maturation

Arsenic (As) is a widespread environmental contaminant, with exposure occurring primarily through contaminated food and water or cigarette smoke. Maternal exposure to As represents a significant risk factor for congenital heart disease in offspring. However, the mechanisms underlying As induced developmental cardiotoxicity remain poorly defined. Pluripotent stem cells provide an excellent platform for studying mechanisms of developmental toxicity. Embryoid bodies (EBs) derived from stem cells, can recapitulate many key events of early embryogenesis including germ layers specification. Human cardiomyocytes are derived from mesodermal progenitors. NKX2.5 governs cardiac specification and morphogenesis, and its mutation produces atrial and ventricular defects in humans. Using an NKX2.5 reporter stem cell line, we modeled mesoderm differentiation in EBs and cardiac induction in a 2D cardiomyocyte differentiation system. In an 8 day differentiation protocol, As (0.05 M; 3.75 ppb) significantly suppressed cardiomyocyte differentiation and cardiac induction. However, As increased mesodermal markers (HAND1, SNAI2, HOPX) gene expression. In contrast, cardiac specific genes, including NKX2.5, GATA4, Troponin T, and alpha actinin, were markedly downregulated in the presence of As. As also reduced expression of genes related to cardiac induction, fibroblast function, and vascular markers in the cardiac organoid model. As impaired cardiomyocyte maturation related gene expressions at concentrations without affecting cardiomyocyte proliferation. In a zebrafish model of early heart development, As increased heart rate and disrupted ion channel gene expression. In conclusion, As inhibits ESC differentiation into cardiomyocytes and disrupts cardiomyocyte maturation. Combining stem cell derived models with zebrafish exposure, this study illuminates adverse outcome pathways for As induced congenital heart defect.

pharmacology and toxicology↗

bioRxiv2026

Tunable gene expression in zebrafish using RiboSCALE

Chemogenetic tools enable conditional control of gene expression during embryonic development and regeneration. However, many conditional tools induce constitutive or one-way activity precluding temporal resolution of gene function or require the use of multiple transgenic lines. We developed an RNA-based chemogenetic approach to induce gene expression in zebrafish embryos and larvae. We demonstrate that a gene of interest can be turned on in a time-dependent and concentration-dependent manner. Using this approach, we have characterized two different aptamers for future investigation.

developmental biology↗

bioRxiv2024

A mutualistic model bacterium is lethal to non-symbiotic hosts via the type VI secretion system

What makes a bacterium pathogenic? Since the early days of germ theory, researchers have categorized bacteria as pathogens or non-pathogens, those that cause harm and those that do not, but this binary view is not always accurate. Vibrio fischeri is an exclusive mutualistic symbiont found within the light organs of Hawaiian bobtail squid. This symbiotic interaction requires V. fischeri to utilize a range of behaviors and produce molecules that are often associated with pathogenicity. This juxtaposition of employing "pathogenic" behaviors for a symbiotic relationship led the field to focus on how V. fischeri establishes a beneficial association with its host. In this study, we observe that V. fischeri induces mortality in zebrafish embryos and Artemia nauplii. Non-lethal doses of V. fischeri leads to zebrafish growth delays and phenotypes indicative of disease. Our data also provide evidence that the conserved type VI secretion system on chromosome I (T6SS1) plays a role in the V. fischeri-induced mortality of zebrafish embryos and Artemia nauplii. These results support the hypothesis that the V. fischeri T6SS1 is involved in eukaryotic cell interactions. Despite its traditional view as a beneficial symbiont, we provide evidence that V. fischeri is capable of harming aquatic organisms, indicating its potential to be pathogenic toward non-symbiotic hosts.

microbiology↗

bioRxiv2024

Effect of Voltage-Gated K+ Channel Inhibition by 4-aminopyridine in Spinal Cord Injury Recovery in Zebrafish

Spinal cord injury (SCI) affects 250,000 to 500,000 individuals annually. After the initial injury, a delayed secondary cascade of cellular responses occurs causing progressive degeneration and permanent disability. One part of this secondary process is disturbance of ionic homeostasis. The K+ channel blocker, 4-aminopyridine (4-AP), is used clinically to alleviate symptoms of multiple sclerosis (MS). Several ongoing studies are being conducted to explore additional areas where 4-AP may have an effect, including stroke, traumatic brain injury, and nervous system recovery after SCI. The goal of our study was to determine whether 4-AP affects functional recovery from SCI in zebrafish (Danio rerio). Using the transgenic line Tg(gfap:EGFP; elavl3:mCherry-CAAX), we created a spinal transection, tracked swim recovery, and measured 4-AP toxicity. We found that constant treatment with 10 M 4-AP increases swimming distance 40%. Live imaging demonstrated that treatment with 4-AP did not accelerate axonal bridging but did affect radial glial cells suggesting that 4-AP affects functional recovery through mechanisms other than axon regeneration. Higher concentrations provided no additional functional benefit and led to increased toxicity in zebrafish.

pharmacology and toxicology↗

bioRxiv2023

Differential roles of diet on development and spinal cord regeneration in larval zebrafish

The zebrafish is a powerful model organism for studying development and regeneration. However, there is a lack of a standardized reference diet. Most studies evaluate the rate of growth, survival and fecundity. In this study, we compare three diets and their effects on growth and regeneration after a spinal cord injury (SCI). Fish were fed daily for one week with daily measurements of overall length and width of spinal injury. Significant different in length after the trial were observed between live feed and commercial feeds. Similarly, differences in rate of regeneration were observed. Our data highlights the need for establishing a standardized diet for regeneration studies to improve research reproducibility.

developmental biology↗

bioRxiv2023

Optimizing spinal cord injury in zebrafish larvae: effects of age on the injury response

Zebrafish are an increasingly popular model to study regeneration after spinal cord injury (SCI). The transparency of larval zebrafish makes them ideal to study cellular processes in real time. Standardized approaches, including age at the time of injury, are not readily available making comparisons of the results with other models challenging. In this study, we systematically examined the response to spinal cord transection of larval zebrafish at three different larval ages (3-, 5-, or 7-days post fertilization (dpf)) to determine whether the developmental complexity of the larvae affects the overall response to SCI. We then used imaging and behavioral analysis to evaluate whether differences existed based on the age of injury. Injury led to increased expression of cytokines associated with the immune response; however, we found that the timing of specific inflammatory markers changed with the age of the injury. We also observed changes in glial and axonal bridging with age. Young larvae (3 dpf) were better able to regenerate axons independent of the glial bridge, unlike older larvae (7 dpf), consistent with results seen in adult zebrafish. Finally, locomotor experiments demonstrated that some swimming behavior occurs independent of glial bridge formation, further highlighting the need for standardization of this model and functional recovery assays. Overall, we found differences based on the age of transection in larval zebrafish, underlining the importance of considering age when designing experiments aimed at understanding regeneration.

developmental biology↗

bioRxiv2019

Targeted cell ablation in zebrafish using optogenetic transcriptional control

Cell ablation is a powerful method for elucidating the contributions of individual cell populations to embryonic development and tissue regeneration. Targeted cell loss in whole organisms has been typically achieved through expression of a cytotoxic or prodrug-activating gene product in the cell type of interest. This approach depends on the availability of tissue-specific promoters, and it does not allow further spatial selectivity within the promoter-defined region(s). To address this limitation, we have developed ablative methods that combine genetically encoded toxins, the tissue specificity afforded by cis-regulatory elements, and the conditionality of optogenetics. Using this integrative approach, we have ablated cells in zebrafish embryos with spatial and temporal precision.

developmental biology↗