Browsing by Author "Tare, Meghana"

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Activation of JNK signaling mediates amyloid-ß-dependent cell death
(Plos One, 2011-09) Tare, Meghana
Alzheimer's disease (AD) is an age related progressive neurodegenerative disorder. One of the reasons for Alzheimer's neuropathology is the generation of large aggregates of Aß42 that are toxic in nature and induce oxidative stress, aberrant signaling and many other cellular alterations that trigger neuronal cell death. However, the exact mechanisms leading to cell death are not clearly understood.
Animal models in the study of Alzheimer's disease and Parkinson's disease: A historical perspective
(Wiley, 2022-01) Tare, Meghana
Alzheimer's disease and Parkinson's disease are two of the most prevalent and disabling neurodegenerative diseases globally. Both are proteinopathic conditions and while occasionally inherited, are largely sporadic in nature. Although the advances in our understanding of the two have been significant, they are far from complete and neither diagnosis nor the current practices in treatment and rehabilitation is adequately helpful. Animal models have historically found application as testing beds for novel therapeutics and continue to be valuable aids in pharmacological research. This review chronicles the development of those models in the context of Alzheimer's and Parkinson's disease, and highlights the shifting paradigms in studying two human-specific conditions in non-human organisms.
A Bird’s Eye View on Cellular Dynamics In Huntington’s Disease
(Current Science, 2023) Tare, Meghana
Huntington's chorea is a rare neurodegenerative disorder caused by the dominant inheritance of the mutated huntingtin gene, housing poly-CAG or polyglutamine repeats. It is characterized by a wide variety of symptoms ranging from chorea and hypokinetic movements to behavioural and cognitive decline, followed by dementia and inevitable death. Over the past 120 years, all available therapeutics have been for the symptomatic management of Huntington's disease (HD) and require supportive physiotherapy and counselling to maximize the efficacy of the treatment. Several animal models have been employed to help elucidate and decrypt the pathophysiology of the disease, and also screen potential therapeutic candidates. In the last few decades, a deeper understanding of the cellular and molecular dynamics associated with HD has helped shed light on the mechanisms involved in disease progression. Genetic intervention for early detection, spreading awareness about HD and its symptoms, and training professionals in the nuances of the disease condition can significantly improve the lifestyle of patients. This article aims at summarizing the complex pathogenesis of HD at the cellular level using various disease models and available therapeutics
A Cell Biology Laboratory Exercise to Study Sub- Cellular Organelles in Drosophila
(University of Dayton, 2008) Tare, Meghana
The fast changing scenario of undergraduate education puts emphasis on introducing students to hands-on techniques as part of their laboratory courses. In order to cater to large numbers of students and the time constraints involved with undergraduate level laboratory courses, there is a need for development of experiments that are cost effective and can be completed in a defined time frame. We have devised a laboratory exercise for teaching cell biology using the Drosophila melanogaster model. Drosophila can be reared in a short period of time in a cost effective manner. We used Drosophila tissue to study the sub-cellular organization of eukaryotic cells using fluorescent markers. The idea of this lab exercise is to: (a) familiarize students with the underlying principles of cell structure and function and its application to diverse areas of research, (b) allow students to sharpen their observation and quantitative microscopy skills, and (c) minimize the preparation time for the instructor.
Characterization of functional amyloid curli in biofilm formation of an environmental isolate Enterobacter cloacae SBP-8. Antonie Van Leeuwenhoek
(Springer, 2023-05) Jha, Prabhat Nath; Tare, Meghana
The biofilm formation by bacteria is a complex process that is strongly mediated by various genetic and environmental factors. Biofilms contribute to disease infestation, especially in chronic infections. It is, therefore important to understand the factors affecting biofilm formation. This study reports the role of a functional amyloid curli in biofilm formation at various abiotic surfaces, including medical devices, by an environmental isolate of Enterobacter cloacae (SBP-8) which has been known for its pathogenic potential. A knockout mutant of csgA, the gene encoding the major structural unit of curli, was created to study the effect of curli on biofilm formation by E. cloacae SBP-8. Our findings confirm the production of curli at 25 °C and 37 °C in the wild-type strain. We further investigated the role of curli in the attachment of E. cloacae SBP-8 to glass, enteral feeding tube, and foley latex catheter. Contrary to the previous studies reporting the curli production below 30 °C in the majority of biofilm-forming bacterial species, we observed its production in E. cloacae SBP-8 at 37 °C. The formation of more intense biofilm in wild-type strain on various surfaces compared to curli-deficient strain (ΔcsgA) at both 25 °C and 37 °C suggested a prominent role of curli in biofilm formation. Further, electron and confocal microscopy studies demonstrated the formation of diffused monolayers of microbial cells on the abiotic surfaces by ΔcsgA strain as compared to the thick biofilm by respective wild-type strain, indicating the involvement of curli in biofilm formation by E. cloacae SBP-8. Overall, our findings provide insight into biofilm formation mediated by curli in E. cloacae SBP-8. Further, we show that it can be expressed at a physiological temperature on all surfaces, thereby indicating the potential role of curli in pathogenesis
COVID-19 infection and metabolic comorbidities: Mitigating role of nutritional sufficiency and drug – nutraceutical combinations of vitamin D
(Elsevier, 2023-03) Deepa, P. R.; Tare, Meghana
The vulnerability of human health is amplified in recent times with global increase in non-communicable diseases (due to lifestyle changes and environmental insults) and infectious diseases (caused by newer pathogens and drug-resistance strains). Clinical management of diseases is further complicated by disease severity caused by other comorbid factors. Drug-based therapy may not be the sole approach, particularly in scenarios like the COVID-19 pandemic, where there is no specific drug against SARS-CoV-2. Nutritional interventions are significant in armouring human populations in disease prevention, and as adjunctive therapy for disease alleviation. Amidst ongoing clinical trials to determine the efficacy of Vit. D against infections and associated complications, this review examines the pleiotropic benefits of nutritional adequacy of vitamin D (Vit. D) in combating viral infections (COVID-19), its severity and complications due to co-morbidities (obesity, diabetes, stroke and Kawasaki disease), based on research findings and clinical studies. Supplements of Vit. D in combination with other nutrients, and drugs, are suggested as promising preventive-health and adjunct-treatment strategies in the clinical management of viral infections with metabolic comorbidities.
Cullin-4 regulates Wingless and JNK signaling-mediated cell death in the Drosophila eye
(Springer Nature, 2016-12) Tare, Meghana
In all multicellular organisms, the fundamental processes of cell proliferation and cell death are crucial for growth regulation during organogenesis. Strict regulation of cell death is important to maintain tissue homeostasis by affecting processes like regulation of cell number, and elimination of unwanted/unfit cells. The developing Drosophila eye is a versatile model to study patterning and growth, where complex signaling pathways regulate growth and cell survival. However, the molecular mechanisms underlying regulation of these processes is not fully understood. In a gain-of-function screen, we found that misexpression of cullin-4 (cul-4), an ubiquitin ligase, can rescue reduced eye mutant phenotypes. Previously, cul-4 has been shown to regulate chromatin remodeling, cell cycle and cell division. Genetic characterization of cul-4 in the developing eye revealed that loss-of-function of cul-4 exhibits a reduced eye phenotype. Analysis of twin-spots showed that in comparison with their wild-type counterparts, the cul-4 loss-of-function clones fail to survive. Here we show that cul-4 clones are eliminated by induction of cell death due to activation of caspases. Aberrant activation of signaling pathways is known to trigger cell death in the developing eye. We found that Wingless (Wg) and c-Jun-amino-terminal-(NH2)-Kinase (JNK) signaling are ectopically induced in cul-4 mutant clones, and these signals co-localize with the dying cells. Modulating levels of Wg and JNK signaling by using agonists and antagonists of these pathways demonstrated that activation of Wg and JNK signaling enhances cul-4 mutant phenotype, whereas downregulation of Wg and JNK signaling rescues the cul-4 mutant phenotypes of reduced eye. Here we present evidences to demonstrate that cul-4 is involved in restricting Wg signaling and downregulation of JNK signaling-mediated cell death during early eye development. Overall, our studies provide insights into a novel role of cul-4 in promoting cell survival in the developing Drosophila eye.
Domain specific genetic mosaic system in the Drosophila eye
(Wiley, 2012-10) Tare, Meghana
Genetic mosaic approach is commonly used in the Drosophila eye by completely abolishing or misexpressing a gene within a subset of cells to unravel its role during development. Classical genetic mosaic approach involves random clone generation in all developing fields. Consequently, a large sample size needs to be screened to generate and analyze clones in specific domains of the developing eye. To address domain specific functions of genes during axial patterning, we have developed a system for generating mosaic clones by combining Gal4/UAS and flippase (FLP)/FRT system which will allow generation of loss-of-function as well as gain-of-function clones on the dorsal and ventral eye margins. We used the bifid-Gal4 driver to drive expression of UAS-FLP. This reagent can have multiple applications in (i) studying spatio-temporal function of a gene during dorso-ventral (DV) axis specification in the eye, (ii) analyzing genetic epistasis of genes involved in DV patterning, and (iii) conducting genome wide screens in a domain specific manner. genesis 51:68–74, 2013. © 2012 Wiley Periodicals, Inc.
Dorsal eye selector pannier (pnr) suppresses the eye fate to define dorsal margin of the Drosophila eye
(Elsiever, 2010-10) Tare, Meghana
Axial patterning is crucial for organogenesis. During Drosophila eye development, dorso-ventral (DV) axis determination is the first lineage restriction event. The eye primordium begins with a default ventral fate, on which the dorsal eye fate is established by expression of the GATA-1 transcription factor pannier (pnr). Earlier, it was suggested that loss of pnr function induces enlargement in the dorsal eye due to ectopic equator formation. Interestingly, we found that in addition to regulating DV patterning, pnr suppresses the eye fate by downregulating the core retinal determination genes eyes absent (eya), sine oculis (so) and dacshund (dac) to define the dorsal eye margin. We found that pnr acts downstream of Ey and affects the retinal determination pathway by suppressing eya. Further analysis of the “eye suppression” function of pnr revealed that this function is likely mediated through suppression of the homeotic gene teashirt (tsh) and is independent of homothorax (hth), a negative regulator of eye. Pnr expression is restricted to the peripodial membrane on the dorsal eye margin, which gives rise to head structures around the eye, and pnr is not expressed in the eye disc proper that forms the retina. Thus, pnr has dual function, during early developmental stages pnr is involved in axial patterning whereas later it promotes the head specific fate. These studies will help in understanding the developmental regulation of boundary formation of the eye field on the dorsal eye margin.
Drosophila Adult Eye Model to Teach Scanning Electron Microscopy in an Undergraduate Cell Biology Laboratory
(University of Dayton, 2009) Tare, Meghana
We have devised an undergraduate laboratory exercise to study tissue morphology using fruit fly, Drosophila melanogaster, as the model organism. Drosophila can be reared in a cost effective manner in a short period of time. This experiment was a part of the undergraduate curriculum of the cell biology laboratory course aimed to demonstrate the use of Scanning Electron Microscopy (SEM) technique to study the morphology of adult eye of Drosophila. The adult eye of Drosophila is a compound eye, which comprises of 800 unit eyes, and serves as an excellent model for SEM studies. We used flies that were mutant for Lobe (L), eyeless (ey), and pannier (pnr) for our studies. The mutant flies exhibit different morphologies of the adult eye.
An E3 ubiquitin ligase, cullin-4 regulates retinal differentiation in Drosophila eye
(Wiley, 2020-09) Tare, Meghana
During organogenesis, cell proliferation is followed by the differentiation of specific cell types to form an organ. Any aberration in differentiation can result in develop- mental defects, which can result in a partial to a near-complete loss of an organ. We employ the Drosophila eye model to understand the genetic and molecular mecha- nisms involved in the process of differentiation. In a forward genetic screen, we iden- tified, cullin-4 (cul-4 ), which encodes an E3 ubiquitin ligase, to play an important role in retinal differentiation. During development, cul-4 is known to be involved in pro- tein degradation, regulation of genomic stability, and regulation of cell cycle. Previ- ously, we have reported that cul-4 regulates cell death during eye development by downregulating Wingless (Wg)/Wnt signaling pathway. We found that loss-of- function of cul-4 results in a reduced eye phenotype, which can be due to onset of cell death. However, we found that loss-of-function of cul-4 also affects retinal development by downregulating retinal determination (RD) gene expression. Early markers of retinal differentiation are dysregulated in cul-4 loss of function conditions, indicating that cul-4 is necessary for differentiation.
Editorial: Protein misfolding, altered mechanisms and neurodegeneration
(Frontiers, 2023-02) Tare, Meghana
Neurodegenerative diseases (NDs) like Alzheimer's disease (AD), Parkinson's disease (PD), Amyotrophic lateral sclerosis (ALS), Frontotemporal lobe degeneration (FTLD), Polyglutamine diseases such as Huntington's disease (HD), Spinocerebellar ataxias (SCAs) etc., are a group of debilitating disorders that affects millions of people worldwide and have no cure to-date. Despite the advancement in our understanding of molecular and genetic mechanisms underlying these NDs, only a limited symptom-based treatment options are available. As the life expectancy increases there is an increase in the number of ND patients, which will seriously challenge the availability of resources and will impact a nation's economy. There is an urgent need to develop an affordable healthcare system and find effective treatment options to provide better clinical regimens to cure these diseases. NDs affect neurons, neuronal connections associated with memory, cognition, thinking, strength, sensation, movements, learning, co-ordination, and other abilities. Although the causative factors of NDs varies from one to another and the differences in the disease symptoms could be many, these diseases share some common features. One of the common pathological hallmarks among the most NDs is aggregation or deposition of misfolded proteins. Compelling evidence from neuropathological, genetic, animal models studies, and other approaches have strongly supported the fact that accumulation of misfolded protein aggregates triggers a series of detrimental events, which results in synaptic alterations, neuronal cell loss, and significantly contributes toward disease pathogenesis.
Emerging relationship between the gut microbiota and neurodegenerative disorders
(Springer, 2024-08) Marathe, Sandhya Amol; Tare, Meghana
A growing body of evidence indicates that the multitude of organisms residing in our gut can profoundly affect our health. These organisms are loosely termed as gut microbiota and have been known to affect the function as well as the behavioral aspects of human health. Recent research shows that the microorganisms in our gut play a crucial role in determining our health and susceptibility to disease. Newly identified intricacies of connection between nervous system and gut microbiota are specially intriguing, since nervous system intersects and in a manner regulates almost every other function of the body. Interestingly, gut microbiota has been found to be affected in cases of nervous system disorders, including neurodegeneration, such as but not limited to Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and multiple sclerosis. The number of people worldwide with neurodegenerative disorders grows yearly, but effective treatments with few side effects remain limited. There is a new avenue of translational research, which evaluates the gut-brain-microbiome axis for management and therapeutic ideas for neurodegenerative disorders. It is therefore important to understand the newer intervention techniques using microbiota, which can be employed for holistic cure of neurodegenerative disorders. This chapter encompasses a comprehensive review of the relationship between gut microbiota in the context of specific neurodegenerative disorders.
Extracellular Reactive Oxygen Species Drive Apoptosis-Induced Proliferation via Drosophila Macrophages
(Elsiever, 2016-03) Tare, Meghana
Apoptosis-induced proliferation (AiP) is a compensatory mechanism to maintain tissue size and morphology following unexpected cell loss during normal development, and may also be a contributing factor to cancer and drug resistance. In apoptotic cells, caspase-initiated signaling cascades lead to the downstream production of mitogenic factors and the proliferation of neighboring surviving cells. In epithelial cells of Drosophila imaginal discs, the Caspase-9 ortholog Dronc drives AiP via activation of Jun N-terminal kinase (JNK); however, the specific mechanisms of JNK activation remain unknown. Here we show that caspase-induced activation of JNK during AiP depends on an inflammatory response. This is mediated by extracellular reactive oxygen species (ROSs) generated by the NADPH oxidase Duox in epithelial disc cells. Extracellular ROSs activate Drosophila macrophages (hemocytes), which in turn trigger JNK activity in epithelial cells by signaling through the tumor necrosis factor (TNF) ortholog Eiger. We propose that in an immortalized (“undead”) model of AiP, signaling back and forth between epithelial disc cells and hemocytes by extracellular ROSs and TNF/Eiger drives overgrowth of the disc epithelium. These data illustrate a bidirectional cell-cell communication pathway with implication for tissue repair, regeneration, and cancer.
A glimpse into dorso-ventral patterning of the Drosophila eye
(Wiley, 2011-10) Tare, Meghana
During organogenesis in all multi-cellular organisms, axial patterning is required to transform a single layer organ primordium into a three-dimensional organ. The Drosophila eye model serves as an excellent model to study axial patterning. Dorso-ventral (DV) axis determination is the ﬁrst lineage restriction event during axial patterning of the Drosophila eye. The early Drosophila eye primordium has a default ventral fate, and the dorsal eye fate is established by onset of dorsal selector gene pannier (pnr) expression in a group of cells on the dorsal eye margin. The boundary between dorsal and ventral com- partments called the equator is the site for Notch (N) activation, which triggers cell proliferation and dif- ferentiation. This review will focus on (1) chronology of events during DV axis determination; (2) how early division of eye into dorsal and ventral compartments contributes towards the growth and pat- terning of the ﬂy retina, and (3) functions of DV patterning genes.
Homeotic Gene teashirt (tsh) Has a Neuroprotective Function in Amyloid-Beta 42 Mediated Neurodegeneration
(Plos One, 2013-11) Tare, Meghana
Alzheimer's disease (AD) is a debilitating age related progressive neurodegenerative disorder characterized by the loss of cognition, and eventual death of the affected individual. One of the major causes of AD is the accumulation of Amyloid-beta 42 (Aβ42) polypeptides formed by the improper cleavage of amyloid precursor protein (APP) in the brain. These plaques disrupt normal cellular processes through oxidative stress and aberrant signaling resulting in the loss of synaptic activity and death of the neurons. However, the detailed genetic mechanism(s) responsible for this neurodegeneration still remain elusive.
Insights Into the Dynamics and Composition of Biofilm Formed by Environmental Isolate of Enterobacter cloacae
(Frontiers, 2022-07) Jha, Prabhat Nath; Tare, Meghana
Bacterial biofilms are clinically admissible and illustrate an influential role in infections, particularly those related to the implant of medical devices. The characterization of biofilms is important to understand the etiology of the diseases. Enterobacter cloacae are known for causing infections by forming biofilms on various abiotic surfaces, such as medical devices. However, a detailed characterization in terms of morphology and the molecular composition of the formed biofilms by this bacterium is sparse. The present study provides insights into the biofilm formation of E. cloacae SBP-8, an environmental isolate, on various surfaces. We performed assays to understand the biofilm-forming capability of the SBP-8 strain and characterized the adhering potential of the bacteria on the surface of different medical devices (foley latex catheter, enteral feeding tube, and glass) at different temperatures. We found that medical devices exhibited strong colonization by E. cloacae SBP-8. Using field emission-scanning electron microscopy (FE-SEM) studies, we characterized the biofilms as a function of time. It indicated stronger biofilm formation in terms of cellular density and EPS production on the surfaces. Further, we characterized the biofilm employing surface-enhanced Raman spectroscopy (SERS) and identified the vast heterogenic nature of the biofilm-forming molecules. Interestingly, we also found that this heterogeneity varies from the initial stages of biofilm formation until the maturation and dispersion. Our studies provide insights into biofilm composition over a period of time, which might aid in understanding the biofilm dispersion phases, to enhance the presently available treatment strategies.
Molecular Genetic Mechanisms of Axial Patterning: Mechanistic Insights into Generation of Axes in the Developing Eye
(Springer, 2013) Tare, Meghana
Non-apoptotic enteroblast-specific role of the initiator caspase Dronc for development and homeostasis of the Drosophila intestine
(Springer Nature, 2021-01) Tare, Meghana
The initiator caspase Dronc is the only CARD-domain containing caspase in Drosophila and is essential for apoptosis. Here, we report that homozygous dronc mutant adult animals are short-lived due to the presence of a poorly developed, defective and leaky intestine. Interestingly, this mutant phenotype can be significantly rescued by enteroblast-specific expression of dronc+ in dronc mutant animals, suggesting that proper Dronc function specifically in enteroblasts, one of four cell types in the intestine, is critical for normal development of the intestine. Furthermore, enteroblast-specific knockdown of dronc in adult intestines triggers hyperplasia and differentiation defects. These enteroblast-specific functions of Dronc do not require the apoptotic pathway and thus occur in a non-apoptotic manner. In summary, we demonstrate that an apoptotic initiator caspase has a very critical non-apoptotic function for normal development and for the control of the cell lineage in the adult midgut and therefore for proper physiology and homeostasis.
Non-apoptotic enteroblast-specific role of the initiator caspase Dronc for development and homeostasis of the Drosophila intestine
(Nature, 2021-01) Tare, Meghana
The initiator caspase Dronc is the only CARD-domain containing caspase in Drosophila and is essential for apoptosis. Here, we report that homozygous dronc mutant adult animals are short-lived due to the presence of a poorly developed, defective and leaky intestine. Interestingly, this mutant phenotype can be significantly rescued by enteroblast-specific expression of dronc+ in dronc mutant animals, suggesting that proper Dronc function specifically in enteroblasts, one of four cell types in the intestine, is critical for normal development of the intestine. Furthermore, enteroblast-specific knockdown of dronc in adult intestines triggers hyperplasia and differentiation defects. These enteroblast-specific functions of Dronc do not require the apoptotic pathway and thus occur in a non-apoptotic manner. In summary, we demonstrate that an apoptotic initiator caspase has a very critical non-apoptotic function for normal development and for the control of the cell lineage in the adult midgut and therefore for proper physiology and homeostasis.