No description available.

To understand the gene regulatory network (GRN) governing caudal hindbrain formation in embryonic zebrafish, several early expressed factors have been manipulated, and multiple genetic mutants have been characterized. Such analyses have identified morphogens such as Retinoic Acid (RA) and Fibroblast growth factors (FGFs), as well as transcription factors like hoxb1b, hoxb1a, hnf1ba, and valentino as being required for rhombomere (r) r4-r6 formation in zebrafish. Considering that the caudal hindbrain is relatively complex – for instance, unique sets of neurons are formed in each rhombomere segment – it is likely that additional essential genes remain to be identified and integrated into the caudal hindbrain GRN. Our results reveal that r4 gene expression is unaffected by the individual loss of hoxb1b, hoxb1a or RA, but is under the combinatorial regulation of RA together with hoxb1b. In contrast, r5/r6 gene expression is dependent on RA, FGF, hnf1ba and valentino – as individual loss of these factors abolishes r5/r6 gene expression. Analysis of six mutant lines (gas6, gbx1, sall4, eglf6, celf2, and greb1l) did not reveal rhombomere or neuronal defects, but transcriptome analysis of one line (gas6 mutant) identified expression changes for genes involved in several developmental processes – suggesting that these genes may have subtle roles in hindbrain development. We conclude that r4-r6 formation is relatively robust, such that very few genes are absolutely required for this process. However, there are mechanistic differences in r4 versus r5/r6, such that no single factor is required for r4 development while several genes are individually required for r5/r6 formation.

Improved therapeutic strategies for patients with leukemia remain in great demand and beckon better understanding of the mechanisms underlying leukemic treatment resistance and relapse. Accordingly, discoveries in leukemic pathophysiology have been achieved in various animal models. Danio rerio—commonly known as the zebrafish—is a vertebrate organism well suited for the investigation of human leukemia. Zebrafish have a conserved hematopoietic program and unique experimental strengths. Recent technological advances in zebrafish research including efficient transgenesis, precise genome editing, and straightforward transplantation techniques have led to the generation of numerous zebrafish leukemia models. Additionally, improved imaging techniques, combined with the transparency of zebrafish, have revealed exquisite details of leukemic initiation, progression, and regression. Finally, advances in high-throughput drug screening in zebrafish are likely to hasten the discovery of novel anti-leukemic agents. Zebrafish provide a reliable experimental system for leukemic disease research and one in which investigators have accumulated knowledge concerning the genetic underpinnings of leukemic transformation and treatment resistance. Without doubt, zebrafish are rapidly expanding our understanding of disease mechanism and are helping to shape therapeutic strategy for improved patient outcomes.

Indiana University-Purdue University Indianapolis (IUPUI) / Diabetes is a morbid metabolic disorder that affects almost 500 million people worldwide. Although multiple factors contribute to diabetes pathogenesis, pancreatic islet inflammation and dysfunction are shared characteristics of its major forms. 12- lipoxygenase (12-LOX), an enzyme involved in lipid metabolism, has been implicated in islet inflammation. 12-LOX generates reactive oxygen species (ROS) that activate inflammation and serve as major contributors to islet dysfunction. Importantly, since ROS are transient moieties, they are challenging to study in vivo. Hence, establishing better animal models of ROS-mediated stress is critical to facilitate the discovery and preclinical testing of novel diabetes therapeutics. Here, I have adapted a zebrafish model of conditional β-cell injury, which is regulated by the administration of the prodrug metronidazole (MTZ), to study responses to ROS in vivo. I demonstrate that with MTZ treatment, ROS are generated within β-cells and subsequently exhibit recruitment of macrophages into the islet and induction of β-cell death. I utilized this model to uncover roles for macrophages and 12-LOX during islet injury. Excessive macrophage infiltration exacerbates islet inflammation and dysfunction. Interestingly, on the depletion of macrophages in zebrafish, I observed that β-cells recovered normal function upon cessation of prodrug treatment. This suggests that infiltrating macrophages promote maladaptive inflammation and premature removal of damaged β-cells. Thus, limiting the macrophage infiltration may be a therapeutic approach to restoring β-cell function. Based on the established roles of 12-LOX in other contexts, I hypothesized that its inhibition would prevent the localized infiltration of proinflammatory macrophages. To test this, I used both zebrafish and mouse models and observed a significant reduction in macrophage migration upon loss of 12- LOX activity. Furthermore, I found that expression of CXCR3, a crucial receptor regulating migration, was significantly reduced in 12-LOX loss-of-function macrophages. These data suggest a role for 12-LOX in macrophages, which is conserved across species. Collectively, my study reveals novel roles for 12-LOX in macrophage function and provides testable therapeutic targets for the resolution of inflammation-induced damage in the pancreatic islets. / 2020-11-19

No description available.

No description available.

No description available.

Delta-8-tetrahydrocannabinol (THC), although less potent than THC, can still reduce memory cognition and anxiety. However, Delta-8 can have adverse effects at high doses, like inducing anxiety, confusion, and hallucinations. The brain of Danio rerio (zebrafish) resembles human neuroanatomical and neurochemical pathways and demonstrates robust behavioral phenotypes, making zebrafish an excellent model organism for memory and anxiety. Subjects will be fed 5mg of Delta 8-THC before entering the experimental apparatus. Fish for both memory and anxiety tests will be observed and recorded through Noldus Ethovision Software. For testing memory, five female and five male zebrafish will be individually placed in a three-compartment memory tank. One side of the memory tank will have a star shape, while the other side will have a circle shape. About .83mg of commercial fish flakes will be administered to the fish on the circle side in the first trial, then on the star side in the second trial, and will continue on either side for 20 trials. Correct responses will be scored when the fish are present on the side of the tank used to present the fish flakes. We hypothesize that there will be fewer correct responses for fish fed with Delta-8-THC than the control. For testing anxiety, ten male and female zebrafish will be fed 5mg of Delta 8-THC before entering the diving tank. Typically, zebrafish experiencing anxiety will stay at the bottom of the diving tank, but if they are relaxed, they will be at the top. We hypothesize that fish fed with Delta-8-THC will spend more time at the top of the diving tank than the control.

Thesis advisor: Sarah K. McMenamin / Thesis advisor: Vicki Losick / Proper bone development requires coordination and timing of specific morphogenetic events, and relative shifts in these temporal processes can change morphology. Thyroid hormone (TH) plays an important role in regulating the timing of vertebrate skeletogenesis, and the hormone induces the profound skeletal shape changes that occur during amphibian metamorphosis. Like humans, zebrafish do not undergo an ecological metamorphosis; yet TH is essential in coordinating postembryonic developmental processes. In particular, several elements of the craniofacial skeleton that continue to ossify and remodel during later stages of development are sensitive to TH titer. My aims focus on the role of TH in regulating skeletal growth and shape changes in zebrafish. To examine changes in the entire zebrafish skeleton during normal postembryonic development, I generated a skeletal reference of microCT scans of zebrafish ranging from early juvenile through adult stages (Chapter 2). After defining the normal changes that wild-type zebrafish undergo, I hypothesized that TH coordinates the developmental shape changes and determined the role of TH in stimulating developmental shape change in zebrafish skulls and its effects on skeletogenic cell populations (Chapter 3). Finally, I investigated whether phenotypes induced by altered TH levels mirror some of the evolutionary diversity seen across Danioninae craniofacial skeletons (Chapter 4). My research elucidates the role of TH in the regulation of bone growth and shape change in a vertebrate system and provides new insights into the natural craniofacial diversity of Danioninae. / Thesis (PhD) — Boston College, 2024. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Biology.

Hypoxia as a stressor has physiological implications that have been a focal point for many physiological studies in recent years. In some studies, hypoxia had large effects on the organ tissue degeneration, which ultimately effects multiple ecological processes. These organ tissue studies played a part in the development of new fields like neurocardiology, a specialty that studied the relationship between the brain and the heart. This thesis focuses on how hypoxia-induced cardiac arrest alters the amounts of GLYT2, a glycine reuptake transporter, in the central nervous system of zebrafish, Danio rerio. At 7 days post-fertilization (dpf), zebrafish were exposed to acute, severe hypoxia until they lost equilibrium, and minutes later, subsequent cardiac arrest occurred. Zebrafish were then placed into recovery groups to measure the GLYT2 levels at multiple points in zebrafish recovery. Fish were then sacrificed, and their brains dissected. Using immunofluorescence, the outer left optic tectum of the zebrafish was imaged, and mean image pixel fluorescent intensity was taken. There were significant changes (one-way ANOVA) in the levels of GLYT2 compared to that of the control groups during the course of recovery. GLYT2 levels continued to rise through the 24-hour recovery mark but did not show significant difference after 3 hours of recovery. This suggest that GLYT2 levels increased rapidly in the first 3 hours of recovery and continued to increase through 24 hours at a slower rate. Changes in GLYT2 levels may affect motor and sensory information, movement, visualization, and audition in these zebrafish. Further research should be conducted to determine how long it takes for GLYT2 levels to return to baseline, as well as behavioral measurements through each recovery period as it relates to glycine function.