Life Sciences Commons^™

Investigation Of Notch Signaling In Cone Fate Specification In Vertebrate Retina, Xueqing Chen

Dissertations, Theses, and Capstone Projects

In the vertebrate retina, cone photoreceptors are crucial for high acuity color vision. Several retinal diseases lead to loss of cones and there is a need to identify the normal developmental genesis of these cells to inform the development of stem cell-based therapies. Cone genesis has previously been shown to be repressed by Notch signaling, however, the mechanism by which Notch signaling controls cone fate determination is still unclear. It has been identified that cone photoreceptors are formed from multipotent retinal progenitor cells (RPCs) that first generate genetically-defined, restricted RPCs with limited mitotic and fate potential to preferentially form cones …

Molecular Mechanisms Underlying Cell Fate Choice Within Specific Retinal Lineages, Estie Schick

Dissertations, Theses, and Capstone Projects

During development, retinal progenitor cells (RPCs) divide to form all of the cell types that make up the retina. Multipotent RPCs are competent to generate all retinal cell types, while restricted RPCs form specific lineages of cells. In particular, one genetically-defined RPC type preferentially gives rise to cone photoreceptors and horizontal cells. Many of the mechanisms that are responsible for directing cell fate choice within this lineage are unknown. This thesis largely focuses on examining the development of specific cell types and subtypes from restricted RPCs and on investigating the gene regulatory events that underlie cone photoreceptor and horizontal cell …

Evolution And Development Of The Seed Coat In Gymnosperms, Cecilia Zumajo

Dissertations, Theses, and Capstone Projects

Gymnosperms and angiosperms are the most abundant plant lineages on earth and constitute a turning point in the evolution of plants because they are at the origin of the seed, a key morphological and developmental novelty in the evolution of land plant. Although the morphological variation of the seed, across seed plants, may on its own, explain the complexity of this structure, the origin, and evolution are even more, the understanding of these topics is still under discussion. Evidence shows that previous studies have often lacked the component of gene expression, particularly in species that are not model species. The …

Development And Maintenance Of The Thymic Epithelial Microenvironment, Shami Chakrabarti

Dissertations, Theses, and Capstone Projects

The thymus plays a critical role in adaptive immunity by providing a suitable microenvironment for developing and selecting the functional self-tolerant T-cell population. Thymic epithelial cells play an essential role in the development of a naïve, self-tolerant T-cell population. Paradoxically thymus undergoes acute age-related involution, which in turn causes loss of functional T-cell populations. Involution reduces the functionality of the thymus markedly, but the thymus can still develop self-tolerant naïve T-cells. It is crucial to understand how the thymic microenvironment is maintained to provide a suitable T-cell population for life. It has been previously demonstrated that the thymic epithelial homeostasis …

Regulation Of A Messenger: Raising Oskar, It Takes A Village, Livia V. Bayer

Dissertations, Theses, and Capstone Projects

D. melanogaster oogenesis serves as an excellent system to study the life of an mRNA. Tremendous work has been done to understand the numerous complex mechanisms of mRNA regulation, still there is still so much that is yet to be discovered. In this thesis, I present studies I carried out to address several aspects of oskar mRNA post-transcriptional regulation. Leading me to extend our current understanding of the carefully controlled regulation of oskar mRNA life cycle via a myriad of proteins. I found that a specific NPC component, Nup154 is necessary not only for its export from the nucleus, but …

Gene Regulation And Cell Fate Choice In The Developing Vertebrate Retina, Sruti Patoori

Dissertations, Theses, and Capstone Projects

The diverse neuronal cell types in the vertebrate retina all originate from multipotent retinal progenitor cells (RPCs). These undergo a series of molecular changes driven by developmental gene regulatory networks (GRNs) as they divide to generate RPCs which are more restricted in their potential fates. It is crucial to understand these GRNs and changes to gene expression in order to understand how cell identity is established during retinal development. In particular, the GRN that promotes the development of cone photoreceptors and horizontal cells is not well-defined. This work focuses on two approaches to further elucidate the components of this regulatory …

Probing The Limits Of Singular Gene Expression Through The Activity Of High Representation Odorant Receptor Transgenes, Eugene Lempert

Dissertations, Theses, and Capstone Projects

Singular gene expression is a common phenomenon in biology, making its appearance in immunoglobulin selection, protocadherin expression, X chromosome-inactivation, random monoallelic expression, and olfactory receptor choice. Singularity involves an activation and a feedback step. The mechanisms of singular gene choice have some capacity to integrate additional member genes while still maintaining singularity, but will activate an additional member if an earlier choice was incapable of triggering the feedback step. Odorant Receptor (OR) genes are substantially divergent from each other in terms of coding sequence, promoter structure, and genomic locus, all of which plays a role in how many Olfactory Sensory …

Dictyostelium Discoideum Protein Kinase C-Orthologue Pkca Regulates The Actin Cytoskeleton Through Interaction With Phospholipase D And P21-Activated Kinase, Sean Singh

Dissertations, Theses, and Capstone Projects

Proper regulation of the actin cytoskeleton is crucial to many cellular processes. Many of these processes are regulated by extracellular signaling cues, which direct changes in the actin cytoskeleton, resulting in changes to cellular morphology, and directed motility. The social amoeba, Dictyostelium discoideum, is used as a simple model system to study the translation of extracellular signals to the actin cytoskeleton. When starved, these unicellular amoebae undergo a multicellular developmental process characterized by a tightly regulated sequence of signaling events. This results in chemotaxis and formation of a multicellular aggregate, and ultimately cell differentiation and the formation of a fruiting …

Towards A Mathematical Model Of Motility Using Dictyostelium Discoideum: Proteins And Geometric Features That Regulate Bleb-Based Motility, Zully Santiago

Dissertations, Theses, and Capstone Projects

A variety of biological functions depend on actin organization. The organization of actin is tightly regulated by a plethora of extracellular and intracellular signaling, scaffolding, and actin-binding proteins. Dysfunctions in this regulation lead to immune diseases, increased susceptibility to pathogens, neurodegenerative diseases, developmental disorders, and cancer metastasis. A variety of actin-dependent processes, including cell motility, are regulated by several proteins of interest: Paxillin, a scaffolding protein; WASP, an actin nucleating protein; SCAR/WAVE, another WASP family actin nucleating protein; Talin, a cortex-to-membrane binding protein; Myosin II, an F-actin contracting motor protein; and Protein Kinase C, a protein kinase. D. discoideum cells …

The 5-Ht1a-R Knockout Mouse As A Model Of Later Life Anxiety Disorders: Implications For Sex Differences, Tatyana Budylin

Dissertations, Theses, and Capstone Projects

Anxiety affects nearly twice as many women as it affects men across all cultures and economic groups. Importantly, girls have a higher chance of inheriting anxiety disorders than boys, and many anxiety disorders appear at a very young age. However, little is known about sex differences in brain and behavioral development and how they relate to anxiety in adulthood. Serotonin 1A receptor (5-HT_1A-R) mediated signaling has been implicated in depression and anxiety, however most studies that focus on the involvement of the 5-HT_1A-R have been conducted in adults. Little is known about how the 5-HT_{1A …}

A Novel Kinesin Adapter Directly Mediates Dendritic Mrna Localization During Synapse Development, Hao Wu

Dissertations, Theses, and Capstone Projects

Cytoskeleton based active transport with motor proteins is essential for mRNA localization and local protein translation in animal cells, yet how mRNA granules interact with motor proteins remains poorly understood. Using an unbiased screen for interaction between mRNA binding proteins (RBP) and motor proteins, we identified protein interacting with APP tail 1 (PAT1) as a potential direct adapter between the β-actin mRNA Zipcode-binding protein 1 (ZBP1) and Kinesin-1 motor complex.

Mouse PAT1 is similar to the Kinesin Light Chain (KLC) in amino acid sequence and binds directly to KLC. High-resolution images from structured illumination microscopy (SIM) indicates that synaptic stimulation …

The Integration Of Multiple Sources Of Sonic Hedgehog In The Spinal Cord Contribute To The Production Of First-Born Oligodendrocyte Precursor Cells Which Become Critical For Synapse Remodeling In Response To Adult Motor Neuron Injury, Lev Starikov

Dissertations, Theses, and Capstone Projects

Oligodendrocyte precursor cells (OPCs) arise sequentially first from a ventral and then from a dorsal precursor domain during spinal cord development. Whether the sequential production of OPCs is of physiological significance has not been examined. Here I show that interrupting Sonic hedgehog (Shh) signaling originating from nascent ventricular zone derivatives (VZD), motor neurons and the lateral floor plate, almost completely blocks ventral but not dorsal oligodendrogenesis without noticeably affecting early tissue patterning and embryonic development. In the absence of ventral OPCs, dorsal OPCs increase proliferation and populate the entire spinal cord with increased density. In these mutant mice, dOPCs take …

Molecular Analysis Of Cone Photoreceptor Genesis From A Specific Retinal Progenitor Population, Diego F. Buenaventura

Dissertations, Theses, and Capstone Projects

There are two types of photosensitive cells of the retina that contribute to image formation: Cone photoreceptors that mediate color discrimination and rods that provide photosensitivity in low-light conditions. Given the importance of cones in high acuity and color vision, deficiencies in this cell type that result from ailments such as retinitis pigmentosa and macular degeneration can lead to a debilitating loss of vision. Currently, one of the most pressing goals in the field of retinal development is the elucidation of the gene regulatory networks (GRN) involved in inducing an undifferentiated cell into becoming a functional cone photoreceptor.

Recently, an …

Integration Of Bmp And Insulin/Igf-1 Signaling Regulates Multiple Homeostatic Functions In Caenorhabditis Elegans, James F. Clark

Dissertations, Theses, and Capstone Projects

The maintenance of homeostatic functions is key to the survival and well-being of an organism. Regulation of homeostasis relies on varied inputs, both intrinsic and extrinsic, to potentiate a web of interconnected signaling relays. Insulin/IGF-1 signaling (IIS) is a well-known regulator of glucose and lipid metabolism, as well as having far reaching effects in other homeostatic mechanisms. On the other hand, bone morphogenetic protein (BMP), a member of the transforming growth factor beta signaling superfamily, is known for its role in differentiation and development, with only recent studies highlighting potential roles in metabolic homeostasis. Here we elucidate new functions for …

The Role Of Pitx Proteins In Early Xenopus Development, Ye Jin

Dissertations, Theses, and Capstone Projects

Embryos of the African clawed frog Xenopus laevis are widely used for the study of early vertebrate development. The cement gland, which secrets mucus to help tadpoles attach to solid supports and live in relative safety, has long been used as a model to study the interplay between cell signaling pathways and transcription factors. It has been proposed that an intermediate level of Bone Morphogenetic Protein (BMP) signaling is essential for cement gland formation. In addition, several transcription factors have been linked to cement gland development. Among them, the homeodomain proteins Pitx1 and the closely related Pitx2c can generate ectopic …

The Role Of T-Box Proteins In Vertebrate Germ Layer Formation And Patterning, Sushma Teegala

Dissertations, Theses, and Capstone Projects

All of the tissues in triploblastic organisms, with the exception of the germ cells, arise from the three germ layers, ectoderm, mesoderm and the endoderm. The identification of the genes that underlie the differentiation of these layers is crucial to our understanding of development. T-box family proteins are DNA-binding transcriptional regulators that play important roles during germ layer formation in the early vertebrate embryo. Well-characterized members of this family, including the transcriptional activators Brachyury and VegT, are essential for the proper formation of mesoderm and endoderm, respectively. To date, T-box proteins have not been shown to play a role in …

Post-Transcriptional Regulation Of The Drosophila Anterior Determinant, Bicoid, John Mclaughlin

Dissertations, Theses, and Capstone Projects

In a wide variety of biological contexts, messenger RNA (mRNA) is known to have a complex and dynamic life cycle. In particular, the localization and translational control of mRNA are essential for proper development in eukaryotes. The fly Drosophila melanogaster is an excellent model for studying these processes. During D. melanogaster oogenesis, several mRNAs are trafficked and localized within the developing egg chamber, and regulated at the translational level to enable embryo patterning. One such mRNA, bicoid, is localized at the anterior of the oocyte and translated in the early embryo, where its encoded protein directs formation of the fly's …

Transcriptional And Post-Transcriptional Regulation Of Histone Variant H2a.Z During Sea Urchin Development, Mihai Hajdu

Dissertations, Theses, and Capstone Projects

Histone variant H2A.Z promotes chromatin accessibility at transcriptional regulatory elements and is developmentally regulated in metazoans. We characterize the transcriptional and post-transcriptional regulation of H2A.Z in the purple sea urchin Strongylocentrotus purpuratus. H2A.Z depletion by antisense translation-blocking morpholino oligonucleotides during early development causes developmental collapse, in agreement with its previously demonstrated general role in transcriptional multipotency. During H2A.Z peak expression in 24-h embryos, endogenous H2A.Z 3’ UTR sequences stabilize GFP mRNAs relative to those with SV40 3’ UTR sequences, although the 3’UTR of H2A.Z does not determine the spatial distribution of H2A.Z transcripts during embryonic and postembryonic development. We …

The Characterization Of Pb2+ Toxicity In Rat Neural Development: An Assessment Of Pb2+ Effects On The Gaba Shift In Neural Networks And Implications For Learning And Memory Disruption, Lorenz Simon Neuwirth

Dissertations, Theses, and Capstone Projects

The toxic effects of Pb2+ on the developing rat nervous system has been investigated to assess early developmental GABAergic disruption and its implications with altering inhibitory learning and memory. This goal was achieved using a multi-systems approach: blood lead levels (clinical physiology), qRT-PCR (molecular genetics), brain and primary neuronal culture immunology (immunohistochemical and cellular approaches), physiological cellular components (synaptosomes and protein expression) and finally through learning and memory assessment with GABA mimetic drug manipulations in the intact animal (behavioral pharmacology). The influence of a 956ppm Pb2+ gestational diet (i.e. from birth to sacrifice) resulted in pup mean blood lead levels …

The Sex Of The Cell Dictates Its Response, Carlos Ganesh Penaloza

Dissertations, Theses, and Capstone Projects

Male and female differences in frequency of occurrence in disease have perplexed scientists for some time. This in part derives from limitations in the systems in which one can evaluate sex differences. At the organismal level, differences can be hidden by a myriad of extensive and complex factors. Additional limitations exist since most biomedical studies are performed almost exclusively on male subjects, as the female hormonal milieu is intrinsically more variable and too troublesome for routine inclusion in research protocols. Research documenting sex differences continues to grow, and while most researchers suggests that sex hormones are at the core of …

Identification And Characterization Of Protein Phopshatases Regulating The Sma/Mab Pathway In C. Elegans, Sheng Xiong

Dissertations, Theses, and Capstone Projects

TGF-beta signaling is a conserved signaling pathway among eukaryotes, which controls various normal cellular responses from cell proliferation to cell death. The mutations in its components are found in developmental disorders and cancer. Therefore, this signaling pathway is extensively investigated so that new therapeutic targets could be discovered and novel drugs could be developed. Previous studies suggested the involvement of phosphatases in regulation of TGF-beta signaling, but these studies were performed in cell culture rather than intact organisms. C. elegans is a tractable organism in which to study signaling in vivo. In C. elegans, growth is controled by a conserved …