Emily Toombs and Tanner Reed to present at Genetics Student Seminar 4/21/2016
LINCing prostaglandin signaling and the regulation of collective cell migration.
Emily Toombs, Tina Tootle
Collective cell migration – the coordinated movement of tightly or loosely associated cells – is important for development and tumor invasion. Many signals are involved in collective cell migration including mechanotransduction, or the transfer of physical force into electrical or chemical signals. While there are many ways in which cells can respond to force, a key mechanism important for cellular migration is the direct connection of the cytoskeleton to the nucleoskeleton via the Linker of Nucleoskeleton and Cytoskeleton (LINC) complex. Alterations in the LINC complex affect nuclear shape, nuclear position, and transcription; however, not much is known about its regulation. Another mechanism regulating cell migration is prostaglandin (PG) signaling. PGs are short-range lipid signals that are implicated in many processes, but, at the same time, little is known about their downstream targets. Our lab has shown that PGs have a large affect on actin remodeling via regulating actin binding proteins. Importantly, actin binding proteins play key roles in mechanotransduction; however, PG signaling has not been previously implicated in regulating mechanotransduction. Using the robust genetic model system of Drosophila, and the well characterized process of oogenesis or follicle development, we present the first evidence that PGs regulate the LINC Complex during the collective and invasive cell migration of the border cells. We hypothesize that PG signaling regulates perinuclear Fascin to control LINC complex function. This hypothesis is based on our prior studies that revealed PG signaling regulates Fascin, an actin bundling protein widely implicated in cell migration. This regulation occurs, in part, by PGs modulating the localization of Fascin, including Fascin’s new perinuclear localization. In both PG synthesis and LINC complex mutant follicles Fascin’s localization to the nuclear periphery is lost. Furthermore, our collaborators have found that in cancer cells, Fascin interacts directly with the LINC Complex. Here we present that loss of PGs or the LINC complex results in delayed and aberrant border cell migration; importantly, Fascin is highly expressed in the border cells. We have identified several tools and approaches that will allow us to quantitatively assess the connection between PG signaling and the LINC complex, as well as the role of Fascin in LINC complex regulation. This research is expected to provide the mechanistic insight into how PGs regulate cellular migration by controlling actin binding proteins to modulate the LINC complex, and, therefore, affect mechanotransduction. These findings will improve our understanding of the functions of PGs, Fascin, and the LINC complex both developmentally and during tumor progression.
Defining the Mediator CDK8 Module in Cardiac Stress
The Mediator complex plays key roles in regulating the transcription of nearly all RNA PolII transcribed genes. Mediator is comprised of four modules: the head, middle, tail (collectively known as the core Mediator), and the CDK8 module which is known to transiently interact with the core Mediator. Classically, it was believed that the composition of Mediator was largely invariant and that the CDK8 module was largely repressive in function. However, recent evidence suggests that during development and cellular differentiation, the composition of core Mediator and CDK8-Mediator changes. This compositional change may account for the large scale transcriptional reprogramming observed in differentiated cells. One component of the CDK8 module is Med13. Cardiac Med13 has been previously shown to regulate cardiac and whole body metabolism, with cardiac expression of Med13 being inversely proportional to susceptibility to metabolic syndromes. In murine cardiomyocytes, the expression of most CDK8 module proteins (including MED13) is decreased following birth. However, recent findings suggest that in cardiomyocytes isolated from mice exposed to cardiac stress, the expression of the CDK8 module proteins is increased. This change in expression may result in a change in composition of CDK8-Mediator, resulting in a modified transcriptome in the cardiomyocytes exposed to cardiac stress. This research aims to define the composition of the CDK8 module as well as components of core Mediator during disease progression and in CDK8 submodule mutants as a means of elucidating the etiology of cardiovascular disease.