No description available.

The Golgi body is responsible for the modification and sorting of proteins and lipids in the secretory pathway. The Golgi must coordinate with other endomembrane compartments in order to target cargo to the correct destination. While our understanding of Golgi function is vast, we can extend our knowledge base by examining the functions of Golgi-associated proteins in developing animals. Lava lamp (Lva) is a Golgi-associated protein and a Drosophila golgin. Previously, Lva was shown to facilitate efficient membrane secretion required for cleavage furrow formation in early embryos. By acting as an adaptor molecule between Golgi and microtubule motility factors, Lva is thought to position Golgi bodies for targeted secretion during cellularization, the Drosophila cleavage stage of development. Here, I further characterize the role of Lva during animal development. I demonstrate that Lva is required for animal viability, and gamete production in females but not males. While Lva is expressed in many tissues, adult fat body cells are the most sensitive to decreased Lva activity, resulting in the disorganization of endomembrane compartments. Furthermore, this disruption in adult fat body cells correlates with a defect in neuroendocrine signaling, altering the activity of juvenile hormone. I propose that Lva activity in adult fat body cells is important for recognizing and/or processing juvenile hormone in order to support Drosophila oogenesis. Lva’s role in cellularization, which is a specialized form of cytokinesis in early embryos, provided insights into the combined processes of actomyosin-based contraction and membrane secretion. While some proteins have been implicated in cellularization, there are thought to be many more that have yet to be identified. In an effort to isolate additional genes involved in animal cell cytokinesis, we screened a unique collection of temperature sensitive (ts) mutations on the X-chromosome of Drosophila melanogaster. At the restrictive temperature, we identified five mutants that displayed a cellularization phenotype. For one of the mutants, fs(1)ts242, we narrowed the mutation to a region on the X chromosome consisting of 17 possible gene candidates. Identification of the gene should provide further elucidation of the mechanisms controlling actomyosin-based contraction and membrane secretion. / text

No description available.

Reduced activity of Fragile X mental retardation protein (FMRP) in brain neurons results in the most common form of heritable mental retardation in humans, Fragile X Syndrome (FXS). FMRP is a selective RNA-binding protein that is implicated in the translational regulation of specific mRNAs in neurons. Although very few direct targets of FMRP have been identified and verified in vivo, FXS is thought to result from the aberrant regulation of potentially hundreds of mRNAs causing defects in neuron morphology and synapse function. Identifying additional targets will be important for elucidating the mechanism of FMRP regulation as well as the etiology of FXS. Drosophila melanogaster offers a unique and powerful system for studying the function of FMRP. Flies with loss of FMRP activity have neuronal and behavioral defects similar to those observed in humans with FXS. Importantly, FMRP regulates common target mRNAs in neurons in both mice and flies. Here, I will describe our discovery of a previously unknown requirement for Drosophila FMRP (dFMRP) during the cleavage stage of early embryonic development. First, we identified a requirement for dFMRP for proper cleavage furrow formation and found that dFMRP functions to regulate the expression of specific target mRNAs during the cleavage stage. Among these is trailer hitch (tral) mRNA, which encodes a translational regulator as well, and represents a new in vivo target of dFMRP translational regulation. In addition, I have identified twenty-eight proteins that change in expression in the absence of dFMRP using a comparative proteomics based screen for dFMRP targets. One of these is the Chaperonin containing tcp-1 complex (CCT), a previously unidentified target, which I found is itself also required for cleavage furrow formation. Finally, we have identified a new dFMRP protein-binding partner, Caprin, and found that together dFMRP and Caprin are required for the proper timing of the MBT. This set of work has led to a better understanding of the mechanism of dFMRP-dependent regulation of cellular morphogenesis in early embryos and has the potential to lead to a better understanding of the etiology of FXS. / text

No description available.

No description available.