Tag: Emily Beck

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

Presenter(s): Emily Niebergall

Faculty Mentor(s): Emily Beck & William Cresko

Poster 54

Session: Sciences

T-cell deficiencies cause a wide range of cell-mediated immunodeficiencies including Severe Combined Immunodeficiency (SCID), Wiskott-Aldrich Syndrome (WAS), and DiGeorge Syndrome. The genetics underlying these deficiencies is complex and the genetic basis of many cell- mediated deficiencies is poorly understood. Due to the invasive nature of prenatal tests used to study T-cell deficiencies in mammals, the development of an outbred immunogenetics model system is needed to understand how genetic variation impacts phenotypic variation of immune disease. Threespine stickleback fish (Gasterosteus aculeatus) provide just such a model. Stickleback are genetically tractable laboratory organisms with a well-annotated genome, and individuals from disparate populations show high levels of genetic variation. Additionally, stickleback provide an excellent system to study T-cell deficiencies, as they experience external fertilization, providing an amenable system to study immune development. To characterize the early development of adaptive immunity in threespine stickleback, we will analyze the expression of known early indicators of adaptive immunity maturation in marine and freshwater stickleback. These include recombination activating genes, rag1 and rag2, and T cell receptor genes, tcr-β and tcr-γ. To analyze gene expression, we will perform rtPCR on a developmental time series of fish. We can then implement in situ hybridization to detect when and where the genes are first expressed, followed by flow cytometry to detect phenotypic variation of T cell activity. Knowing when adaptive immunity onset occurs in threespine stickleback advances these fish as an outbred disease model in immunogenetics studies, allowing manipulative studies of immunological disease phenotypes in the context of genetic variation.

Testing the Centromere-Drive Hypothesis in Primates.

Presenter(s): L. Gomez Gomez

Faculty Mentor(s): Kirstin Sterner & Emily Beck

Poster 52

Session: Sciences

Chromosomal centromeres play a critical role in the process of cell division. Centromeres act as binding sites for microtubules that pull chromosomes apart during mitosis and meiosis. Despite this conserved function, the centromeres themselves can vary in size and sequence content between species. Rapid evolution in these regions can also drive rapid evolution in centromere- associated proteins. Previous work has suggested these rapid changes are likely to accumulate in one of two essential centromere components; either CENP-A or CENP-C. Through compensatory coevolution, positive selection can subsequently cascade into other essential protein complexes resulting in hybrid incompatibility. Cascading selection from the centromere to CENP-A was previously reported in Drosophila by Beck et al. 2015 demonstrating the extension of positive selection to the essential Condensin I complex (SMC2, SMC4, NCAPD2, NCAPG, NCAPH orthologs). To test if kinetochore-associated proteins evolve rapidly in other animals, we examined the sequence of CENP-A and CENP-C and their associated protein complexes, Condensin I and Mis12 (DSN1, MIS12, NSL1, PMF1) respectively, across primates. Sequences were mined from publicly available genomes (21-25 individual species per gene), aligned using Clustal-Omega and manually checked in Mesquite to ensure that protein-coding sequences conformed to codon boundaries. We then used the codeml (PAML) to test for positive selection. Our preliminary data suggests CENP-C may be evolving rapidly showing evidence of positive selection in components of Condensin1 and Mis12 complexes. This finding supports the centromere-drive hypothesis, which suggests the presence of an evolutionary tug-of-war between centromeric DNA and centromere-associated proteins that may shape karyotype evolution.

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 .