During the age of non-avian dinosaurs, ancestors of present-day mammals were likely small insectivores, relegated to nocturnal and subterranean niches. This nocturnal "bottle-neck" is postulated as a driving force of numerous physiological and sensory adaptations including those of the visual system. The consequences of structural mutations of opsins upon spectral sensitivity and environmental adaptation have been studied in great detail, but lacking is knowledge of the potential influence of alterations in gene regulatory networks upon the diversity of cone subtypes and the variation in the ratio of rods and cones observed in diurnal and nocturnal species. Exploiting photoreceptor patterning in cone-dominated zebrafish, we uncovered two independent mechanisms by which the sine oculis homeobox homolog 7 (six7) regulates photoreceptor development. In a genetic screen, we isolated the lots-of-rods-junior (ljrp23ahub) mutation that resulted in an increased number and uniform distribution of rods in otherwise normal appearing larvae. Sequence analysis, genome editing using TALENs and knockdown strategies confirm ljrp23ahub as a hypomorphic allele of six7, a teleost orthologue of six3, with known roles in forebrain patterning and expression of opsins. Based on the lack of protein-coding changes and an identified deletion of a conserved sequence about 40 kb upstream of six7 loci, a cis-regulatory mutation is proposed as the basis of the reduced expression in ljrp23ahub. Comparison of the hypomorphic and knock-out alleles provides evidence of two independent roles in photoreceptor development. EdU and PH3 labeling show that the increase in rod number and uniform distribution is associated with extended mitosis of photoreceptor progenitors, and TUNEL suggest that the lack of green cones is the result of cell death of the cone precursor. These data add six7 to the small but growing list of genes essential for specification and patterning of photoreceptors in non-mammalian vertebrates, and form the basis of a model that underscores the potential of alterations in transcriptional regulation as a mechanism underpinning photoreceptor variation across species. / A Dissertation submitted to the Department of Biological Science in partial fulfillment of the Doctor of Philosophy. / Spring Semester 2016. / March 14, 2016. / development, evolution, photoreceptors, retina, TALENs, zebrafish / Includes bibliographical references. / James M. Fadool, Professor Directing Dissertation; Jamila I. Horabin, University Representative; Brian P. Chadwick, Committee Member; Hank W. Bass, Committee Member; Wu-Min Deng, Committee Member.

The follicular epithelium (FE) of the Drosophila egg chamber is an excellent model system to study cell-cycle regulation, cell differentiation and cell migration in development. During oogenesis, follicle cells sequentially undergo three distinct cell-cycle programs: the mitotic cycle (stage 1-6), endocycle (stage 7-10a), and gene amplification (stage 10b-13). Notch signaling plays a central role in regulating follicle-cell differentiation and cell-cycle switches; its activation and inactivation in follicle cells are essential for the mitotic cycle/endocycle (M/E) and the endocycle/gene amplification (E/A) switches, respectively. In my dissertation, I mainly focus on Notch signaling and its downstream target broad (br). In the first part of the dissertation, I introduce the background information of the egg chamber system, Notch signaling and other associated factors. In the second part, I describe a screen strategy to identify novel genes involved in Notch-mediated follicle cell differentiation and cell cycle switches. In the third part, I select a Notch target gene br from the above-mentioned screen and study its regulation and functions. I will show br, encoding a small group of zinc-finger transcription factors resulting from alternative splicing, is a transcriptional target of Notch nuclear effector Suppressor of Hairless (Su(H)). The early pattern of Br in the FE, uniformly expressed except in the polar cells, is established by Notch signaling around stage 6, through the binding of Su(H) to the br early enhancer (brE) region. My findings also suggest an important role of br in the timing of follicle cell development during the M/E switch. In the fourth part, I report the uniform pattern of Br in the follicular epithelium is gradually lost in the anterior follicle cells (stretched cells and border cells) from stage 9 to 10a during oogenesis. This downregulation of Br is functionally significant for proper stretched-cell stretching. I also find ecdysone and JAK/STAT signaling mediate the downregulation of Notch-maintained Br. Together, My research investigates the complex Notch signaling network, and reveal that Notch-directly-regulated Br interacts with the ecdysone and JAK/STAT pathways, serving as an important spatiotemporal cue for proper cell differentiation and morphogenetic movement during Drosophila oogenesis. / A Dissertation submitted to the Department of Biological Science in partial fulfillment of the Doctor of Philosophy. / Spring Semester, 2015. / February 27, 2015. / broad, ecdysone, follicle cell, JAK/STAT, Notch, oogenesis / Includes bibliographical references. / Wu-Min Deng, Professor Directing Dissertation; Jamila I. Horabin, University Representative; Jonathan Hancock Dennis, Committee Member; Timothy Megraw, Committee Member; Steven John Lenhert, Committee Member.

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Our understanding of speciation has been greatly improved with advances in genomic technology, but most of our knowledge of speciation is still built on research of diploid systems. Polyploids, however, are found in many lineages across the tree of life and exhibit considerably different evolutionary dynamics than diploids. Here, we investigate patterns of population structure and divergence in a system of two allopolyploid species of Mimulus (monkeyflower) that occur sympatrically in Chile: M. luteus and M. cupreus. We find that while the two species have consistent phenotypic differences across the range, they are genetically clustered into a northern and southern population (rather than by species), based on a STRUCTURE analysis of 48 whole-genome paired-end sequences of the two species across six populations in Chile. Using LUMPY and DELLY2 to locate chromosomal structural variants (SVs), we identify hundreds of SVs unique to one species or the other both across the entire range and just within the north or south. We also calculated metrics of divergence (FST and DXY) in 10 kbp regions across the genome and find that these metrics were not greater within SV regions than across the whole genome. However, we did find that inversions occurred at 100–150X greater frequency within the regions of top 1% of FST and DXY values compared to the across the entire genome, indicating that inversions may promote divergence. Overall, we find evidence to suggest that M. luteus and M. cupreus are currently undergoing sympatric speciation, and that inversions may help promote divergence in this system while deletions and duplications likely do not. Additionally, SV diversity is much higher than generally assumed, perhaps due to increased genomic instability in these allopolyploids, warranting future studies looking into the effects of SVs on species divergence.

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No description available.

This study investigated burden in a convenience, nonrandom sample of 120 spousal caregivers of cardiac patients, who resided at home in the Richmond, VA area, had health insurance, and received medical care from private providers. Using Vitaliano's theory that burden is a function of stressors and personal vulnerability moderated by psychological resources and social supports, the study examined the relationships between those five constructs.;Burden was measured by the Brief Symptom Inventory and Montgomery's Scales of Objective and Subjective Burden. The Hassles and Uplifts Scales was used to measure stressors; demographic data and the Self control, Responsibility, Socialization, Psychological Mindedness, Tolerance, Flexibility, Self acceptance, and Achievement via conformance scales of the CPI, to measure personal vulnerability; the Ways of Coping Questionnaire, psychological resources; Vaux's SS-B, the availability of social supports; and ORIENT, the willingness to utilize social supports.;Four research hypotheses based on Vitaliano's theory were investigated. Although the data conclusively supported only one, i.e., that low vulnerability scores would have positive correlations with high scores on social support, they did appear to support a multicausal explanation for the development of burden. Variables within each of the constructs had practical and statistical significance in correlation with the burden variables. Significant relationships existed between the three burden measures and certain variables: the appraised severity of the stressors; age, education, and income; the personality traits of responsibility, self-acceptance, flexibility, self control and psychological mindedness, as measured by those CPI scales; the use of escape/avoidance and/or planful problem solving as coping styles; the availability of social supports; and the willingness to use those supports. Personal vulnerability also had a significant relationship with how stressed individuals used their social supports. The data suggested that the three types of burden were affected differently by the variables. One unexpected finding was that frequency of hassles had a weak, but significant, negative relationship with burden. Despite that finding, it was concluded that the biopsychosocial model offered a valid explanation for the development of burden.

The ribbonfish family Trachipteridae (Lampridiformes) includes three well-defined genera (Trachipterus, Desmodema, and Zu), which are distributed worldwide throughout the pelagic marine environment as with most families of Lampridiformes, drastic changes in morphology occur throughout ontogeny due to extreme allometric growth. Combined with the rarity of specimens, this has led to the description of different life history stages as different species, rather than as part of the ontogenetic continuum of a single species. There is significant uncertainty concerning the ontogeny, distribution, nomenclature, number and phylogenetic affinity of trachipterid and other lampridiform genera.;The first chapter of my dissertation is a taxonomic review of of the family Trachipteridae. This chapter provides updated genus (Trachipterus, Desmodema, and Zu) and species descriptions ( Desmodema and Zu) and a synthesis of life history, biogeographic, and ontogenetic data for trachipterid fishes, including examination of an abundance of material from the western Pacific Ocean. Additionally, numerous new morphological observations are described and an updated key to the trachipterid genera, applicable to both juvenile and adult stages, is provided.;The phylogenetic systematics of all lampridiform genera (Metavelifer, Velifer, Lampris, Lophotus, Eumecichthys, Radiicephalus, Agrostichthys, Regalecus, Trachipterus, Desmodema, Zu) is examined in the second chapter of my dissertation. I used 62 morphological characters from across the ontogenetic continuum to test proposed hypotheses of genus-level relationships of Trachipteridae and familial monophyly of the Lampridiformes. All lampridiform families were recovered as monophyletic except for the Lophotidae, resulting in Eumecichthys as incertae sedis. The suborder Taeniosomoidei is proposed to reflect the monophyletic clade consisting on long-bodied lampridiforms. Trachipteridae is recovered as monophyletic sister group to Regalecidae. The superfamily Trachipteroidea is proposed to recognize this clade. However, within the Trachipteridae, a monophyletic clade consisting of Trachipterus + Zu is recovered but with low support.