Faculty Bibliography

The COP9 signalosome removes Nedd8 modifications from the Cullin subunits of ubiquitin ligase complexes, reducing their activity. Here we show that mutations in the Drosophila COP9 signalosome subunit 1b (CSN1b) gene increase the activity of ubiquitin ligases that contain Cullin 1. Analysis of CSN1b mutant phenotypes revealed a requirement for the COP9 signalosome to prevent ectopic expression of Epidermal growth factor receptor (EGFR) target genes. It does so by protecting Capicua, a transcriptional repressor of EGFR target genes, from EGFR pathway-dependent ubiquitination by a Cullin 1/SKP1-related A/Archipelago E3 ligase and subsequent proteasomal degradation. The CSN1b subunit also maintains basal Capicua levels by protecting it from a separate mechanism of degradation that is independent of EGFR signaling. As a suppressor of tumor growth and metastasis, Capicua may be an important target of the COP9 signalosome in cancer.

We describe a fluorescence in situ hybridization method that permits detection of the localization and abundance of single mRNAs (smFISH) in cleared whole-mount adult Drosophila brains. The approach is rapid and multiplexable and does not require molecular amplification; it allows facile quantification of mRNA expression with subcellular resolution on a standard confocal microscope. We further demonstrate single-mRNA detection across the entire brain using a custom Bessel beam structured illumination microscope (BB-SIM).

Spatial information is critical to the interrogation of developmental and tissue-level regulation of gene expression. However, this information is usually lost when global mRNA levels from tissues are measured using reverse transcriptase PCR, microarray analysis or high-throughput sequencing. By contrast, single-molecule fluorescence in situ hybridization (smFISH) preserves the spatial information of the cellular mRNA content with subcellular resolution within tissues. Here we describe an smFISH protocol that allows for the quantification of single mRNAs in Drosophila embryos, using commercially available smFISH probes (e.g., short fluorescently labeled DNA oligonucleotides) in combination with wide-field epifluorescence, confocal or instant structured illumination microscopy (iSIM, a super-resolution imaging approach) and a spot-detection algorithm. Fixed Drosophila embryos are hybridized in solution with a mixture of smFISH probes, mounted onto coverslips and imaged in 3D. Individual fluorescently labeled mRNAs are then localized within tissues and counted using spot-detection software to generate quantitative, spatially resolved gene expression data sets. With minimum guidance, a graduate student can successfully implement this protocol. The smFISH procedure described here can be completed in 4-5 d.

PROBLEM: To better prepare graduating medical students to transition to the professional responsibilities of residency, 10 medical schools are participating in an Association of American Medical Colleges pilot to evaluate the feasibility of explicitly teaching and assessing 13 Core Entrustable Professional Activities for Entering Residency. The authors focused on operationalizing the concept of entrustment as part of this process. APPROACH: Starting in 2014, the Entrustment Concept Group, with representatives from each of the pilot schools, guided the development of the structures and processes necessary for formal entrustment decisions associated with students' increased responsibilities at the start of residency. OUTCOMES: Guiding principles developed by the group recommend that formal, summative entrustment decisions in undergraduate medical education be made by a trained group, be based on longitudinal performance assessments from multiple assessors, and incorporate day-to-day entrustment judgments by workplace supervisors. Key to entrustment decisions is evidence that students know their limits (discernment), can be relied on to follow through (conscientiousness), and are forthcoming despite potential personal costs (truthfulness), in addition to having the requisite knowledge and skills. The group constructed a developmental framework for discernment, conscientiousness, and truthfulness to pilot a model for transparent entrustment decision making. NEXT STEPS: The pilot schools are studying a number of questions regarding the pathways to and decisions about entrustment. This work seeks to inform meaningful culture change in undergraduate medical education through a shared understanding of the assessment of trust and a shared trust in that assessment.

OBJECTIVES: To identify the association between social and moderate alcohol consumption and functional outcomes after surgical management of orthopaedic fractures. DESIGN: Prospective cohort study. SETTING: Level 1 trauma center. PATIENTS/PARTICIPANTS: Seven hundred eighty-four patients who were operatively treated for an isolated orthopaedic fracture were prospectively followed. Patients were categorized into groups according to self-reported drinking frequencies based on NIAAA guidelines. MAIN OUTCOME MEASUREMENTS: SMFA scores at baseline, 3, 6, and 12 months postoperatively; postoperative complications; and subsequent operations. RESULTS: There were 367 (46.8%) abstinent, 327 (41.7%) social, 52 (6.6%) moderate, and 38 (4.8%) heavy drinkers. Mean SMFA scores of social and moderate drinkers were significantly lower than those of abstinent patients at 3-, 6-, and 12-month follow-ups, denoting better functional outcomes (social: 24.3 vs. 30.5, P = 0.001; 14.8 vs. 21.5, P < 0.005; and 10.1 vs. 18.8, P < 0.005); (moderate: 18.3 vs. 30.5, P = 0.001; 9.7 vs. 21.5, P = 0.001; and 5.4 vs. 18.8, P < 0.005). Multiple linear regression revealed that social drinking and baseline SMFA scores were the only statistically significant independent predictors of lower SMFA scores at 12 months after surgery. CONCLUSIONS: Social to moderate drinking may have a protective effect on functional outcomes at 3, 6, and 12 months after surgery. Social drinking may also have a protective effect on postoperative complications and reoperation rates. Further studies should be performed to fully appreciate the clinical effect of social and moderate drinking after operative treatment of orthopaedic fractures. LEVEL OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Endothelial cell adhesion and migration are critical steps of the angiogenic process, whose dysfunction is associated with tumor growth and metastasis. The TRPM8 channel has recently been proposed to play a protective role in prostate cancer by impairing cell motility. However, the mechanisms by which it could influence vascular behavior are unknown. Here, we reveal a novel non-channel function for TRPM8 that unexpectedly acts as a Rap1 GTPase inhibitor, thereby inhibiting endothelial cell motility, independently of pore function. TRPM8 retains Rap1 intracellularly through direct protein-protein interaction, thus preventing its cytoplasm-plasma membrane trafficking. In turn, this mechanism impairs the activation of a major inside-out signaling pathway that triggers the conformational activation of integrin and, consequently, cell adhesion, migration, in vitro endothelial tube formation, and spheroid sprouting. Our results bring to light a novel, pore-independent molecular mechanism by which endogenous TRPM8 expression inhibits Rap1 GTPase and thus plays a critical role in the behavior of vascular endothelial cells by inhibiting migration.

The GIPC family adaptor proteins mediate endocytosis by tethering cargo proteins to the myosin VI motor. The structural mechanisms for the GIPC/cargo and GIPC/myosin VI interactions remained unclear. PlexinD1, a transmembrane receptor that regulates neuronal and cardiovascular development, is a cargo of GIPCs. GIPC-mediated endocytic trafficking regulates PlexinD1 signaling. Here we unravel the mechanisms of the interactions among PlexinD1, GIPCs and myosin VI by a series of crystal structures of these proteins in apo or bound states. GIPC1 forms a domain-swapped dimer in an autoinhibited conformation that hinders binding of both PlexinD1 and myosin VI. PlexinD1 binding to GIPC1 releases the autoinhibition, promoting its interaction with myosin VI. GIPCs and myosin VI interact through two distinct interfaces and form an open-ended alternating array. Our data support that this alternating array underlies the oligomerization of the GIPC/Myosin VI complexes in solution and cells.