Granting access: Development of a formal course to demystify and promote predoctoral fellowship applications for graduate students

Strong scientific writing skills are the foundation of a successful research career and require training and practice. Although these skills are critical for completing a PhD, most students receive little formal writing instruction prior to joining a graduate program. In 2015, the University of Iowa Medical Scientist Training Program (MSTP) addressed this issue by developing the scientific writing course Grant Writing Basics (GWB). Here we describe the structure of this course and its effectiveness. GWB is an interactive, workshop-based course that uses a National Institutes of Health (NIH) F30 predoctoral fellowship proposal as a platform for building writing expertise. GWB incorporates established pedagogical principles of adult learning, including flipped classrooms, peer teaching, and reiterative evaluation. Time spent in class centers on active student analysis of previously submitted fellowship applications, discussion of writing resources, active writing, facilitated small group discussion of critiques of student writing samples, revision, and a discussion with a panel of experienced study section members and a student who completed a fellowship submission. Outcomes of GWB include a substantial increase in the number of applications submitted and fellowships awarded. Rigorous evaluation provides evidence that learning objectives were met and that students gained confidence in both their scientific writing skills and their ability to give constructive feedback. Our findings show that investment in formal training in written scientific communication provides a foundation for good writing habits, and the knowledge and skills needed to succeed in this vital aspect of a scientific research career. Furthermore, they highlight that evaluation is valuable in guiding course evolution. Strategies embedded in GWB can be adapted for use in any graduate program to advance scientific writing skills among its trainees.

Notch signaling induces rapid degradation of achaete-scute homolog 1

In neural development, Notch signaling plays a key role in restricting neuronal differentiation, promoting the maintenance of progenitor cells. Classically, Notch signaling causes transactivation of Hairy-enhancer of Split (HES) genes which leads to transcriptional repression of neural determination and differentiation genes. We now report that in addition to its known transcriptional mechanism, Notch signaling also leads to rapid degradation of the basic helix-loop-helix (bHLH) transcription factor human achaete-scute homolog 1 (hASH1). Using recombinant adenoviruses expressing active Notch1 in small-cell lung cancer cells, we showed that the initial appearance of Notch1 coincided with the loss of hASH1 protein, preceding the full decay of hASH1 mRNA. Overexpression of HES1 alone was capable of down-regulating hASH1 mRNA but could not replicate the acute reduction of hASH1 protein induced by Notch1. When adenoviral hASH1 was coinfected with Notch1, we still observed a dramatic and abrupt loss of the exogenous hASH1 protein, despite high levels of ongoing hASH1 RNA expression. Notch1 treatment decreased the apparent half-life of the adenoviral hASH1 protein and increased the fraction of hASH1 which was polyubiquitinylated. The proteasome inhibitor MG132 reversed the Notch1-induced degradation. The Notch RAM domain was dispensable but a lack of the OPA and PEST domains inactivated this Notch1 action. Overexpression of the hASH1-dimerizing partner E12 could protect hASH1 from degradation. This novel function of activated Notch to rapidly degrade a class II bHLH protein may prove to be important in many contexts in development and in cancer.

The Drosophila tumor suppressor expanded regulates growth, apoptosis, and patterning during development

The Drosophila expanded (ex) gene encodes a protein thought to play a role in signaling at apical junctions of epithelial cells. Previous studies have characterized this gene as a tumor suppressor involved in regulating the growth of a subset of Drosophila imaginal discs (Boedigheimer, M., Laughon, A., 1993. expanded: a gene involved in the control of cell proliferation in imaginal discs, Development 118, 1291-1301); although ex negatively regulates cell proliferation in the developing wing, it appeared to have a conflicting role in the eye. In contrast, our analysis of the loss-of-function phenotype indicates that ex does, in fact, regulate growth in the eye. We also show that this gene plays a role in patterning of the eye, mainly at the level of planar polarity. Our studies further demonstrate that, contrary to what was expected based on loss-of-function data, the tissue reduction phenotypes resulting from Ex overexpression are attributable to the induction of apoptotic cell death. Taken together, our data suggest that Ex is a versatile molecule that plays a role in most of the processes that govern disc development.

Neoplastic transformation by truncated alleles of human NOTCH1/TAN1 and NOTCH2

The Notch genes of Drosophila melanogaster and vertebrates encode transmembrane receptors that help determine cell fate during development. Although ligands for Notch proteins have been identified, the signaling cascade downstream of the receptors remains poorly understood. In human acute lymphoblastic T-cell leukemia, a chromosomal translocation damages the NOTCH1 gene. The damage apparently gives rise to a constitutively activated version of NOTCH protein. Here we show that a truncated version of NOTCH1 protein resembling that found in the leukemic cells can transform rat kidney cells in vitro. The transformation required cooperation with the E1A oncogene of adenovirus. The transforming version of NOTCH protein was located in the nucleus. In contrast, neither wild-type NOTCH protein nor a form of the truncated protein permanently anchored to the plasma membrane produced transformation in vitro. We conclude that constitutive activation of NOTCH similar to that found in human leukemia can contribute to neoplastic transformation. Transformation may require that the NOTCH protein be translocated to the nucleus. These results sustain a current view of how Notch transduces a signal from the surface of the cell to the nucleus.

Intracellular cleavage of Notch leads to a heterodimeric receptor on the plasma membrane

Previous models for signal transduction via the Notch pathway have depicted the full-length Notch receptor expressed at the cell surface. We present evidence demonstrating that the Notch receptor on the plasma membrane is cleaved. This cleavage is an evolutionarily conserved, general property of Notch and occurs in the trans-Golgi network as the receptor traffics toward the plasma membrane. Although full-length Notch is detectable in the cell, it does not reach the surface. Cleavage results in a C-terminal fragment, N(TM), that appears to be cleaved N-terminal to the transmembrane domain, and an N-terminal fragment, N(EC), that contains most of the extracellular region. We provide evidence that these fragments are tethered together on the plasma membrane by a link that is sensitive to reducing conditions, forming a heterodimeric receptor.

Comparative aspects of Notch signaling in lower and higher eukaryotes

The Drosophila melanogaster Notch gene encodes a receptor that is part of a cell-cell signaling mechanism that is used throughout the development of the fly to regulate a wide variety of cell fate decisions, including some neuronal decisions. The Caenorhabditis elegans Notch-like genes lin-12 and glp-1 play roles that are similar to that of Notch, and studies of this signaling pathway in both organisms have led to models of how the pathway might function. Recent developments in the study of Notch signaling include the isolation of Notch homologs from a variety of vertebrate species. Here we compare what has been learned from studies of Notch-related genes in vertebrates to what is known about Notch signaling in invertebrates, and we discuss the implications of these data for existing models of Notch pathway signaling.

Deltex acts as a positive regulator of Notch signaling through interactions with the Notch ankyrin repeats

We present a molecular and genetic analysis which elucidates the role of deltex in the Notch signaling pathway. Using the yeast ‘interaction trap’ assay, we define the protein regions responsible for heterotypic interactions between Deltex and the intracellular domain of Notch as well as uncover homotypic interaction among Deltex molecules. The function of the Deltex-Notch interaction domains is examined by in vivo expression studies. Taken together, data from overexpression of Deltex fragments and from studies of physical interactions between Deltex and Notch, suggest that Deltex positively regulates the Notch pathway through interactions with the Notch ankyrin repeats. Experiments involving cell cultures indicate that the Deltex-Notch interaction prevents the cytoplasmic retention of the Suppressor of Hairless protein, which otherwise is sequestered in the cytoplasm via association with the Notch ankyrin repeats and translocates to the nucleus when Notch binds to its ligand Delta. On the basis of these findings, we propose a model wherein Deltex regulates Notch activity by antagonizing the interaction between Notch and Suppressor of Hairless.

Alterations in Notch signaling in neoplastic lesions of the human cervix

The development of cancer is a cellular process that reflects and is partly driven by alterations in cell determination. Mutations in various molecules responsible for cell determination have been identified as being oncogenic, but little is known about the involvement of normal cell fate-determining mechanisms in the oncogenic process. The Notch pathway defines an evolutionarily conserved, general cell interaction mechanism that controls fundamental aspects of cell determination during vertebrate and invertebrate development. We have explored the involvement of the human Notch pathway in human cervical tissues, which define a cellular environment where cell fate changes take place and where neoplastic conditions have been well characterized. Our evidence suggests that Notch expression is associated with cell populations that are undergoing cell fate changes and that Notch activity can be used to monitor cell fate abnormalities in cervical as well as other epithelial neoplasias.

Human homologs of a Drosophila Enhancer of split gene product define a novel family of nuclear proteins

Notch and the m9/10 gene (groucho) of the Enhancer of split (E(spI)) complex are members of the "Notch group" of genes, which is required for a variety of cell fate choices in Drosophila. We have characterized human cDNA clones encoding a family of proteins, designated TLE, that are homologous to the E(spI) m9/10 gene product, as well as a novel Notch-related protein. The TLE genes are differentially expressed and encode nuclear proteins, consistent with the presence of sequence motifs associated with nuclear functions. The structural redundancy implied by the existence of more than one TLE and Notch-homologous gene may be a feature of the human counterparts of the developmentally important Drosophila Notch group genes.

Photosensitized DNA breaks and DNA-to-protein crosslinks induced in human cells by antitumor agent gilvocarcin V

The antitumor agent gilvocarcin V (GV) is photoactivated to a genotoxic form by low fluences of near-ultraviolet radiation. Activation of GV by monochromatic 450-nm radiation causes two specific DNA changes in human P3 cells in culture as shown by alkaline elution techniques: single-strand breaks (i.e., alkali-labile sites plus frank strand scissions) and DNA-to-protein covalent bond crosslinks. When GV is present with the cells during irradiation, the yields of these damages are increased. Fluence and concentration studies show that the induction of both DNA lesions occurs at unusually low concentrations of drug and fluences of radiation. Both breaks and crosslinks are readily detectable after exposure to less than 100 kJ m-2 of 405 nm-radiation at a GV concentration of 7.5 X 10(-9) M. These results indicate a possible potential for use of GV in human tumor photochemotherapy.