Tag: Earning your Stripes

Advancing threespine stickleback as an outbred immunogenetics model by pinpointing the onset of adaptive immunity

Presenter(s): Emily Niebergall—Biology

Faculty Mentor(s): William Cresko, Emily Beck

Session 4: Earning your Stripes

Understanding when the onset of the adaptive immune system occurs is important for understanding host-microbe interactions and etiology of disease . While the onset of adaptive immunity has been studied in inbred animal models, i .e . mice and zebrafish, these laboratory models lack the genetic diversity found in humans and may not be appropriate for all studies . We are advancing threespine stickleback fish (Gasterosteus aculeatus) as a novel outbred immunogenetics model to elucidate the complexities of these interactions in the context of genetic variation . It is currently unknown when adaptive immunity is onset in threespine stickleback . To pinpoint the timing of onset of adaptive immunity, we looked at the expression of an early adaptive immune gene known to be involved in T-lymphocyte development throughout a developmental time series . T-lymphocytes are a primary adaptive immune cells able to recognize and elicit a response against pathogens . Early development of these cells utilizes two interconnected protein complexes: CD3 and TCR . The pre-TCR/CD3 supercomplex has been used to study the ontogeny of the immune system and has provided insight into the development of the adaptive immune system . In this study, we chose to focus on cd3d, a gene involved in the CD3 complex . Similar work determining the onset of adaptive immunity in other fish has produced a wide range of results, from 72 hours post fertilization to 20 days post hatching (dph) . We found that by 10 dph, cd3d was expressed in all individuals, with population level variation indicating some may exhibit expression earlier in development .

Understanding microbial modulation of neuronal morphology in zebrafish

Presenter(s): Max Grice—Computer Science

Faculty Mentor(s): Judith Eisen, Joseph Bruckner

Session 4: Earning your Stripes

Increasing evidence supports a role for the intestinal microbiota in modulating host neurodevelopment and behavior, including complex social behaviors . Recent research has also linked the microbiota to neurological disorders including autism spectrum disorder (ASD), depression, Alzheimer’s Disease, and Parkinson’s Disease . However, the mechanisms of these interactions between the host-associated microbiota and neurodevelopment remain unclear . Using zebrafish raised in the absence of the microbiota, or germ-free (GF), our group has found that the microbiota modulates zebrafish social behavior . Normal social behavior requires neurons in a region of the brain called the ventral telencephalon (vTel) . Therefore, we hypothesized that the microbiota may modulate social behavior by altering development of vTel neurons, resulting in changes in vTel neuron morphology . To measure morphology of vTel neurons, we combined sparse mosaic labelling and high- resolution confocal microscopy to image individual vTel neurons . We used Imaris software to segment individual neurons and extract morphological measurements and adapted several software packages to warp and register individual neurons to an average reference brain in each condition . We found that vTel neurons from GF fish are significantly more complex than vTel neurons from their conventionally raised siblings . Together, this work suggests that the microbiota may modulate social behavior by restraining complexity of ventral forebrain neurons . Understanding the specific mechanism through which the microbiota normally modulates social behavior will allow us to better understand microbial modulation of neurodevelopment and therefore construct more effective treatments for neurological disorders that may result from dysbiosis of the host-associated microbiota .

Beta cell regeneration upon the addition of Beta-Cell Expansion Factor A (BefA)

Presenter(s): Robin Black—Biology

Co-Presenter(s):Ian Torrence, Emily Niebergall, Dan Tudorica

Faculty Mentor(s): Karen Guillemin, Michelle Massaquoi

Session 4: Earning your Stripes

All organisms co-exist with a plethora of bacteria, fungi, and viruses living on and within them, collectively known as a microbiota . Previous work has shown that in the absence of the microbiota (after a germ-free derivation), the beta-cells within larval zebrafish fail to develop (Hill et al ., 2016) . Beta-cells are insulin-producing cells found in the pancreas and are vital for glucose uptake in the body . This experiment has practical applications, as Type I diabetes in humans is an autoimmune disease where the body attacks its own beta-cells . Recently, the Guillemin lab has discovered a novel bacterial-secreted protein, Beta-Cell Expansion Factor A (BefA), that is sufficient to rescue beta-cell proliferation within germ-free zebrafish . Although the study found that BefA is critical for beta cell development, its potential role in beta-cell regeneration is unknown . The goal of this study is to test the role of BefA in pancreatic beta-cell regeneration after induced beta-cell death . Using a transgenic line of zebrafish, we validated that we can significantly and specifically ablate beta cells in larval zebrafish . We next plan to ablate beta-cells of conventionally reared (with microbiota) and germ-free zebrafish treated with and without BefA and quantify the number of beta-cells regenerated . We predict that upon the addition of BefA, there will be a rescue in the number of beta-cells . From this experiment we will learn about the potential therapeutic uses of BefA to recover beta-cells and broadly the important roles that gut microbiota play in host homeostasis .