A variety of genetic techniques have been devised to determine cell lineage relationships during tissue development. Some of these systems monitor cell lineages spatially and/or temporally without regard to gene expression by the cells, whereas others correlate gene expression with the lineage under study. The GAL4 Technique for Real-time and Clonal Expression (G-TRACE) system allows for rapid, fluorescent protein-based visualization of both current and past GAL4 expression patterns and is therefore amenable to genome-wide expression-based lineage screens. Here we describe the results from such a screen, performed by undergraduate students of the University of California, Los Angeles (UCLA) Undergraduate Research Consortium for Functional Genomics (URCFG) and high school summer scholars as part of a discovery-based education program. The results of the screen, which reveal novel expression-based lineage patterns within the brain, the imaginal disc epithelia, and the hematopoietic lymph gland, have been compiled into the G-TRACE Expression Database (GED), an online resource for use by the Drosophila research community. The impact of this discovery-based research experience on student learning gains was assessed independently and shown to be greater than that of similar programs conducted elsewhere. Furthermore, students participating in the URCFG showed considerably higher STEM retention rates than UCLA STEM students that did not participate in the URCFG, as well as STEM students nationwide.
Cell-mediated regenerative approaches using muscle progenitor cells hold promises for the treatment of many forms of muscle disorders. Their applicability in the clinic, however, is hindered by the low levels of regeneration obtained after transplantation and the large number of cells required to achieve an effect. To better understand the mechanisms that regulate the temporal switch of replicating muscle progenitor cells into terminally differentiated cells and to develop new strategies that could enhance muscle regeneration, we have developed and performed a high-throughput screening (HTS) capable of identifying genes that play active roles during myogenesis. Secondary and tertiary screens were used to confirm the effects of RNAi in vitro and in vivo and to select for candidate hits that significantly increase regeneration into skeletal muscles. Downregulation of cyclin D2 (CCND2) was shown to dramatically enhance myogenic differentiation of muscle progenitor cells and to induce a robust regeneration after cell transplantation into skeletal muscles of dystrophin-deficient mice. Protein interaction network and pathway analysis revealed that CCND2 directly interacts with the cyclin-dependent kinase Cdk4 to inhibit phosphorylation of the retinoblastoma protein (pRb), thus blocking the activation of the myogenic switch during fusion. These studies identify CCND2 as a new key regulator of terminal differentiation in muscle progenitor cells and open new possibilities for the treatment of many forms of muscle disorders characterized by impaired regeneration and loss of muscle mass.
N, Chessler SD. Extracellular CADM1 interactions influence insulin secretion by rat and human islet -cells and promote clustering of syntaxin-1. Am J Physiol Endocrinol Metab 310: E874 -E885, 2016. First published April 12, 2016 doi:10.1152/ajpendo.00318.2015-Contact between -cells is necessary for their normal function. Identification of the proteins mediating the effects of -cell-to--cell contact is a necessary step toward gaining a full understanding of the determinants of -cell function and insulin secretion. The secretory machinery of the -cells is nearly identical to that of central nervous system (CNS) synapses, and we hypothesize that the transcellular protein interactions that drive maturation of the two secretory machineries upon contact of one cell (or neural process) with another are also highly similar. Two such transcellular interactions, important for both synaptic and -cell function, have been identified: EphA/ephrin-A and neuroligin/neurexin. Here, we tested the role of another synaptic cleft protein, CADM1, in insulinoma cells and in rat and human islet -cells. We found that CADM1 is a predominant CADM isoform in -cells. In INS-1 cells and primary -cells, CADM1 constrains insulin secretion, and its expression decreases after prolonged glucose stimulation. Using a coculture model, we found that CADM1 also influences insulin secretion in a transcellular manner. We asked whether extracellular CADM1 interactions exert their influence via the same mechanisms by which they influence neurotransmitter exocytosis. Our results suggest that, as in the CNS, CADM1 interactions drive exocytic site assembly and promote actin network formation. These results support the broader hypothesis that the effects of cell-cell contact on -cell maturation and function are mediated by the same extracellular protein interactions that drive the formation of the presynaptic exocytic machinery. These interactions may be therapeutic targets for reversing -cell dysfunction in diabetes.cell adhesion molecule 1; SynCam; pancreatic islet; insulin secretion
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