Effect of a Co-Located Bridging Recovery Initiative on Hospital Length of Stay Among Patients With Opioid Use Disorder: The BRIDGE Randomized Clinical Trial.

Importance: Co-located bridge clinics aim to facilitate a timely transition to outpatient care for inpatients with opioid use disorder (OUD); however, their effect on hospital length of stay (LOS) and postdischarge outcomes remains unclear. Objective: To evaluate the effect of a co-located bridge clinic on hospital LOS among inpatients with OUD. Design, Setting, and Participants: This parallel-group randomized clinical trial recruited 335 adult inpatients with OUD seen by an addiction consultation service and without an existing outpatient clinician to provide medication for OUD (MOUD) between November 25, 2019, and September 28, 2021, at a tertiary care hospital affiliated with a large academic medical center and its bridge clinic. Intervention: The bridge clinic included enhanced case management before and after hospital discharge, MOUD prescription, and referral to a co-located bridge clinic. Usual care included MOUD prescription and referrals to community health care professionals who provided MOUD. Main Outcomes and Measures: The primary outcome was the index admission LOS. Secondary outcomes, assessed at 16 weeks, were linkage to health care professionals who provided MOUD, MOUD refills, same-center emergency department (ED) and hospital use, recurrent opioid use, quality of life (measured by the Schwartz Outcome Scale-10), overdose, mortality, and cost. Analysis was performed on an intent-to-treat basis. Results: Of 335 participants recruited (167 randomized to the bridge clinic and 168 to usual care), the median age was 38.0 years (IQR, 31.9-45.7 years), and 194 (57.9%) were male. The median LOS did not differ between arms (adjusted odds ratio [AOR], 0.94 [95% CI, 0.65-1.37]; P = .74). At the 16-week follow-up, participants referred to the bridge clinic had fewer hospital-free days (AOR, 0.54 [95% CI, 0.32-0.92]), more readmissions (AOR, 2.17 [95% CI, 1.25-3.76]), and higher care costs (AOR, 2.25 [95% CI, 1.51-3.35]), with no differences in ED visits (AOR, 1.15 [95% CI, 0.68-1.94]) or deaths (AOR, 0.48 [95% CI, 0.08-2.72]) compared with those receiving usual care. Follow-up calls were completed for 88 participants (26.3%). Participants referred to the bridge clinic were more likely to receive linkage to health care professionals who provided MOUD (AOR, 2.37 [95% CI, 1.32-4.26]) and have more MOUD refills (AOR, 6.17 [95% CI, 3.69-10.30]) and less likely to experience an overdose (AOR, 0.11 [95% CI, 0.03-0.41]). Conclusions and Relevance: This randomized clinical trial found that among inpatients with OUD, bridge clinic referrals did not improve hospital LOS. Referrals may improve outpatient metrics but with higher resource use and expenditure. Bending the cost curve may require broader community and regional partnerships. Trial Registration: ClinicalTrials.gov Identifier: NCT04084392.

Cefepime vs Piperacillin-Tazobactam in Adults Hospitalized With Acute Infection: The ACORN Randomized Clinical Trial.

Importance: Cefepime and piperacillin-tazobactam are commonly administered to hospitalized adults for empirical treatment of infection. Although piperacillin-tazobactam has been hypothesized to cause acute kidney injury and cefepime has been hypothesized to cause neurological dysfunction, their comparative safety has not been evaluated in a randomized clinical trial. Objective: To determine whether the choice between cefepime and piperacillin-tazobactam affects the risks of acute kidney injury or neurological dysfunction. Design, Setting, and Participants: The Antibiotic Choice on Renal Outcomes (ACORN) randomized clinical trial compared cefepime vs piperacillin-tazobactam in adults for whom a clinician initiated an order for antipseudomonal antibiotics within 12 hours of presentation to the hospital in the emergency department or medical intensive care unit at an academic medical center in the US between November 10, 2021, and October 7, 2022. The final date of follow-up was November 4, 2022. Interventions: Patients were randomized in a 1:1 ratio to cefepime or piperacillin-tazobactam. Main Outcomes and Measures: The primary outcome was the highest stage of acute kidney injury or death by day 14, measured on a 5-level ordinal scale ranging from no acute kidney injury to death. The 2 secondary outcomes were the incidence of major adverse kidney events at day 14 and the number of days alive and free of delirium and coma within 14 days. Results: There were 2511 patients included in the primary analysis (median age, 58 years [IQR, 43-69 years]; 42.7% were female; 16.3% were Non-Hispanic Black; 5.4% were Hispanic; 94.7% were enrolled in the emergency department; and 77.2% were receiving vancomycin at enrollment). The highest stage of acute kidney injury or death was not significantly different between the cefepime group and the piperacillin-tazobactam group; there were 85 patients (n = 1214; 7.0%) in the cefepime group with stage 3 acute kidney injury and 92 (7.6%) who died vs 97 patients (n = 1297; 7.5%) in the piperacillin-tazobactam group with stage 3 acute kidney injury and 78 (6.0%) who died (odds ratio, 0.95 [95% CI, 0.80 to 1.13], P = .56). The incidence of major adverse kidney events at day 14 did not differ between groups (124 patients [10.2%] in the cefepime group vs 114 patients [8.8%] in the piperacillin-tazobactam group; absolute difference, 1.4% [95% CI, -1.0% to 3.8%]). Patients in the cefepime group experienced fewer days alive and free of delirium and coma within 14 days (mean [SD], 11.9 [4.6] days vs 12.2 [4.3] days in the piperacillin-tazobactam group; odds ratio, 0.79 [95% CI, 0.65 to 0.95]). Conclusions and Relevance: Among hospitalized adults in this randomized clinical trial, treatment with piperacillin-tazobactam did not increase the incidence of acute kidney injury or death. Treatment with cefepime resulted in more neurological dysfunction. Trial Registration: ClinicalTrials.gov Identifier: NCT05094154.

Protocol and statistical analysis plan for the Antibiotic Choice On ReNal outcomes (ACORN) randomised clinical trial.

INTRODUCTION: Antibiotics are time-critical in the management of sepsis. When infectious organisms are unknown, patients are treated with empiric antibiotics to include coverage for gram-negative organisms, such as antipseudomonal cephalosporins and penicillins. However, in observational studies, some antipseudomonal cephalosporins (eg, cefepime) are associated with neurologic dysfunction while the most common antipseudomonal penicillin (piperacillin-tazobactam) is associated with acute kidney injury (AKI). No randomised control trials have compared these regimens. This manuscript describes the protocol and analysis plan for a trial designed to compare the effects of antipseudomonal cephalosporins and antipseudomonal penicillins among acutely ill patients receiving empiric antibiotics. METHODS AND ANALYSIS: The Antibiotic Choice On ReNal outcomes trial is a prospective, single-centre, non-blinded randomised trial being conducted at Vanderbilt University Medical Center. The trial will enrol 2500 acutely ill adults receiving gram-negative coverage for treatment of infection. Eligible patients are randomised 1:1 to receive cefepime or piperacillin-tazobactam on first order entry of a broad-spectrum antibiotic covering gram-negative organisms. The primary outcome is the highest stage of AKI and death occurring between enrolment and 14 days after enrolment. This will be compared between patients randomised to cefepime and randomised to piperacillin-tazobactam using an unadjusted proportional odds regression model. The secondary outcomes are major adverse kidney events through day 14 and number of days alive and free of delirium and coma in 14 days after enrolment. Enrolment began on 10 November 2021 and is expected to be completed in December 2022. ETHICS AND DISSEMINATION: The trial was approved by the Vanderbilt University Medical Center institutional review board (IRB#210591) with a waiver of informed consent. Results will be submitted to a peer-reviewed journal and presented at scientific conferences. TRIAL REGISTRATION NUMBER: NCT05094154.

Effect of Smartphone App-Based Education on Clinician Prescribing Habits in a Learning Health Care System: A Randomized Cluster Crossover Trial.

Importance: Effective methods for engaging clinicians in continuing education for learning-based practice improvement remain unknown. Objective: To determine whether a smartphone-based app using spaced education with retrieval practice is an effective method to increase evidence-based practice. Design, Setting, and Participants: A prospective, unblinded, single-center, crossover randomized clinical trial was conducted at a single academic medical center from January 6 to April 24, 2020. Vanderbilt University Medical Center clinicians prescribing intravenous fluids were invited to participate in this study. Interventions: All clinicians received two 4-week education modules: 1 on prescribing intravenous fluids and 1 on prescribing opioid and nonopioid medications (counterbalancing measure), over a 12-week period. The order of delivery was randomized 1:1 such that 1 group received the fluid management module first, followed by the pain management module after a 4-week break, and the other group received the pain management module first, followed by the fluid management module after a 4-week break. Main Outcomes and Measures: The primary outcome was evidence-based clinician prescribing behavior concerning intravenous fluids in the inpatient setting and pain medication prescribing on discharge from the hospital. Results: A total of 354 participants were enrolled and randomized, with 177 in group 1 (fluid then pain management education) and 177 in group 2 (pain management then fluid education). During the overall study period, 16 868 questions were sent to 349 learners, with 11 783 (70.0%) being opened: 10 885 (92.4%) of those opened were answered and 7175 (65.9%) of those answered were answered correctly. The differences between groups changed significantly over time, indicated by the significant interaction between educational intervention and time (P = .002). Briefly, at baseline evidence-concordant IV fluid ordered 7.2% less frequently in group 1 than group 2 (95% CI, -19.2% to 4.9%). This was reversed after training at 4% higher (95% CI, -8.2% to 16.0%) in group 1 than group 2, a more than doubling in the odds of evidence-concordant ordering (OR, 2.56, 95% CI, 0.80-8.21). Postintervention, all gains had been reversed with less frequent ordering in group 1 than group 2 (-9.5%, 95% CI, -21.6% to 2.7%). There was no measurable change in opioid prescribing behaviors at any time point. Conclusions and Relevance: In this randomized clinical trial, use of smartphone app learning modules resulted in statistically significant short-term improvement in some prescribing behaviors. However, this effect was not sustained over the long-term. Additional research is needed to understand how to sustain improvements in care delivery as a result of continuous professional development at the institutional level. Trial Registration: ClinicalTrials.gov Identifier: NCT03771482.

Balanced Crystalloid versus Saline in Adults with Traumatic Brain Injury: Secondary Analysis of a Clinical Trial.

Balanced crystalloids may improve outcomes compared with saline for some critically ill adults. Lower tonicity of balanced crystalloids could worsen cerebral edema in patients with intracranial pathology. The effect of balanced crystalloids versus saline on clinical outcomes in patients with traumatic brain injury (TBI) requires further study. We planned an a priori subgroup analysis of TBI patients enrolled in the pragmatic, cluster-randomized, multiple-crossover Isotonic Solutions and Major Adverse Renal Events Trial (SMART) (ClinicalTrials.gov: NCT02444988, NCT02547779). Primary outcome was 30-day in-hospital mortality. Secondary outcomes included hospital discharge disposition (home, facility, death). Regression models adjusted for pre-specified baseline covariates compared outcomes. TBI patients assigned to balanced crystalloids (n = 588) and saline (n = 569) had similar baseline characteristics including Injury Severity Score 19 (10); mean maximum head/neck Abbreviated Injury Score, 3.4 (1.0). Isotonic crystalloid volume administered between intensive care unit admission and first of hospital discharge or 30 days was 2037 (3470) mL and 1723 (2923) mL in the balanced crystalloids and saline groups, respectively (p = 0.18). During the study period, 94 (16%) and 82 (14%) patients (16%) died in the balanced crystalloid and saline groups, respectively (adjusted odds ratio [aOR], 1.03; 95% confidence interval [CI], 0.60 to 1.75; p = 0.913). Patients in the balanced crystalloid group were more likely to die or be discharged to another medical facility (aOR 1.38 [1.02-1.86]; p = 0.04). Overall, balanced crystalloids were associated with worse discharge disposition in critically injured patients with TBI compared with saline. The confidence intervals cannot exclude a clinically relevant increase in mortality when balanced crystalloids are used for patients with TBI.

Assessment of Awake Prone Positioning in Hospitalized Adults With COVID-19: A Nonrandomized Controlled Trial.

Importance: Awake prone positioning may improve hypoxemia among patients with COVID-19, but whether it is associated with improved clinical outcomes remains unknown. Objective: To determine whether the recommendation of awake prone positioning is associated with improved outcomes among patients with COVID-19-related hypoxemia who have not received mechanical ventilation. Design, Setting, and Participants: This pragmatic nonrandomized controlled trial was conducted at 2 academic medical centers (Vanderbilt University Medical Center and NorthShore University HealthSystem) during the COVID-19 pandemic. A total of 501 adult patients with COVID-19-associated hypoxemia who had not received mechanical ventilation were enrolled from May 13 to December 11, 2020. Interventions: Patients were assigned 1:1 to receive either the practitioner-recommended awake prone positioning intervention (intervention group) or usual care (usual care group). Main Outcomes and Measures: Primary outcome analyses were performed using a bayesian proportional odds model with covariate adjustment for clinical severity ranking based on the World Health Organization ordinal outcome scale, which was modified to highlight the worst level of hypoxemia on study day 5. Results: A total of 501 patients (mean [SD] age, 61.0 [15.3] years; 284 [56.7%] were male; and most [417 (83.2%)] were self-reported non-Hispanic or non-Latinx) were included. Baseline severity was comparable between the intervention vs usual care groups, with 170 patients (65.9%) vs 162 patients (66.7%) receiving oxygen via standard low-flow nasal cannula, 71 patients (27.5%) vs 62 patients (25.5%) receiving oxygen via high-flow nasal cannula, and 16 patients (6.2%) vs 19 patients (7.8%) receiving noninvasive positive-pressure ventilation. Nursing observations estimated that patients in the intervention group spent a median of 4.2 hours (IQR, 1.8-6.7 hours) in the prone position per day compared with 0 hours (IQR, 0-0.7 hours) per day in the usual care group. On study day 5, the bayesian posterior probability of the intervention group having worse outcomes than the usual care group on the modified World Health Organization ordinal outcome scale was 0.998 (posterior median adjusted odds ratio [aOR], 1.63; 95% credibility interval [CrI], 1.16-2.31). However, on study days 14 and 28, the posterior probabilities of harm were 0.874 (aOR, 1.29; 95% CrI, 0.84-1.99) and 0.673 (aOR, 1.12; 95% CrI, 0.67-1.86), respectively. Exploratory outcomes (progression to mechanical ventilation, length of stay, and 28-day mortality) did not differ between groups. Conclusions and Relevance: In this nonrandomized controlled trial, prone positioning offered no observed clinical benefit among patients with COVID-19-associated hypoxemia who had not received mechanical ventilation. Moreover, there was substantial evidence of worsened clinical outcomes at study day 5 among patients recommended to receive the awake prone positioning intervention, suggesting potential harm. Trial Registration: ClinicalTrials.gov Identifier: NCT04359797.

Bridging Recovery Initiative Despite Gaps in Entry (BRIDGE): study protocol for a randomized controlled trial of a bridge clinic compared with usual care for patients with opioid use disorder.

BACKGROUND: Patients with substance use disorders are overrepresented among general hospital inpatients, and their admissions are associated with longer lengths of stay and increased readmission rates. Amid the national opioid crisis, increased attention has been given to the integration of addiction with routine medical care in order to better engage such patients and minimize fragmentation of care. General hospital addiction consultation services and transitional, hospital-based "bridge" clinics have emerged as potential solutions. We designed the Bridging Recovery Initiative Despite Gaps in Entry (BRIDGE) trial to determine if these clinics are superior to usual care for these patients. METHODS: This single-center, pragmatic, randomized controlled clinical trial is enrolling hospitalized patients with opioid use disorder (OUD) who are initiating medication for OUD (MOUD) in consultation with the addiction consult service. Patients are randomized for referral to a co-located, transitional, multidisciplinary bridge clinic or to usual care, with the assignment probability being determined by clinic capacity. The primary endpoint is hospital length of stay. Secondary endpoints include quality of life, linkage to care, self-reported buprenorphine or naltrexone fills, rate of known recurrent opioid use, readmission rates, and costs. Implementation endpoints include willingness to be referred to the bridge clinic, attendance rates among those referred, and reasons why patients were not eligible for referral. The main analysis will use an intent-to-treat approach with full covariate adjustment. DISCUSSION: This ongoing pragmatic trial will provide evidence on the effectiveness of proactive linkage to a bridge clinic intervention for hospitalized patients with OUD initiating evidence-based pharmacotherapy in consultation with the addiction consult service. TRIAL REGISTRATION: ClinicalTrials.gov NCT04084392 . Registered on 10 September 2019. The study has been approved by the Vanderbilt Institutional Review Board. The current approved protocol is dated version May 12, 2021.

Learning From What We Do, and Doing What We Learn: A Learning Health Care System in Action.

Different models of learning health systems are emerging. At Vanderbilt University Medical Center, the Learning Health Care System (LHS) Platform was established with the goal of creating generalizable knowledge. This differentiates the LHS Platform from other efforts that have adopted a quality improvement paradigm. By supporting pragmatic trials at the intersection of research, operations, and clinical care, the LHS Platform was designed to yield evidence for advancing content and processes of care through carefully designed, rigorous study. The LHS Platform provides the necessary infrastructure and governance to leverage translational, transdisciplinary team science to inform clinical and operational decision making across the health system. The process transforms a clinical or operational question into a research question amenable to a pragmatic trial. Scientific, technical, procedural, and human infrastructure is maintained for the design and execution of individual LHS projects. This includes experienced pragmatic trialists, project management, data science inclusive of biostatistics and clinical informatics, and regulatory support. Careful attention is paid to stakeholder engagement, including health care providers and the community. Capturing lessons from each new study, the LHS Platform continues to mature with plans to integrate implementation science and to complement clinical and process outcomes with cost and value considerations. The Vanderbilt University Medical Center LHS Platform is now a pillar of the health care system and leads the evolving culture of learning from what we do and doing what we learn.

Embedding Learning in a Learning Health Care System to Improve Clinical Practice.

PROBLEM: In an ideal learning health care system (LHS), clinicians learn from what they do and do what they learn, closing the evidence-to-practice gap. In operationalizing an LHS, great strides have been made in knowledge generation. Yet, considerable challenges remain to the broad uptake of identified best practices. To bridge the gap from generating actionable knowledge to applying that knowledge in clinical practice, and ultimately to improving outcomes, new information must be disseminated to and implemented by frontline clinicians. To date, the dissemination of this knowledge through traditional avenues has not achieved meaningful practice change quickly. APPROACH: Vanderbilt University Medical Center (VUMC) developed QuizTime, a smartphone application learning platform, to provide a mechanism for embedding workplace-based clinician learning in the LHS. QuizTime leverages spaced education and retrieval-based practice to facilitate practice change. Beginning in January 2020, clinician-researchers and educators at VUMC designed a randomized, controlled trial to test whether the QuizTime learning system influenced clinician behavior in the context of recent evidence supporting the use of balanced crystalloids rather than saline for intravenous fluid management and new regulations around opioid prescribing. OUTCOMES: Whether spaced education and retrieval-based practice influence clinician behavior and patient outcomes at the VUMC system level will be tested using the data currently being collected. NEXT STEPS: These findings will inform future directions for developing and deploying learning approaches at scale in an LHS, with the goal of closing the evidence-to-practice gap.

COMPASS: A Pilot Trial of an Early Palliative Care Intervention for Patients With End-Stage Liver Disease.

CONTEXT: Palliative care interventions have shown promise in improving quality of life and reducing health-care utilization among patients with chronic organ failure. OBJECTIVES: To evaluate the effect of a palliative care intervention for adults with end-stage liver disease. METHODS: A randomized controlled trial of patients with end-stage liver disease admitted to the hepatology service at a tertiary referral center whose attending hepatologist indicated they would not be surprised if the patient died in the following year on a standardized questionnaire was performed. Control group patients received usual care. Intervention group patients received inpatient specialist palliative care consultations and outpatient phone follow-up by a palliative care nurse. The primary outcome was time until first readmission. Secondary outcomes included days alive outside the hospital, referral to hospice care, death, readmissions, patient quality of life, depression, anxiety, and quality of end-of-life care over 6 months. RESULTS: The trial stopped early because of difficulties in accruing patients. Of 293 eligible patients, only 63 patients were enrolled, 31 in the intervention group and 32 in the control group. This pace of enrollment was only 25% of what the study had planned, and so it was deemed infeasible to complete. Despite stopping early, intervention group patients had a lower hazard of readmission (hazard ratio: 0.36, 95% confidence interval: 0.16-0.83, P = 0.017) and greater odds of having more days alive outside the hospital than control group patients (odds ratio: 3.97, 95% confidence interval: 1.14-13.84, P = 0.030). No other statistically significant differences were observed. CONCLUSION: Logistical obstacles hindered completion of the trial as originally designed. Nevertheless, a preemptive palliative care intervention resulted in increased time to first readmission and more days alive outside the hospital in the first six months after study entry.

Synaptic roles for phosphomannomutase type 2 in a new Drosophila congenital disorder of glycosylation disease model.

Congenital disorders of glycosylation (CDGs) constitute a rapidly growing family of human diseases resulting from heritable mutations in genes driving the production and modification of glycoproteins. The resulting symptomatic hypoglycosylation causes multisystemic defects that include severe neurological impairments, revealing a particularly critical requirement for tightly regulated glycosylation in the nervous system. The most common CDG, CDG-Ia (PMM2-CDG), arises from phosphomannomutase type 2 (PMM2) mutations. Here, we report the generation and characterization of the first Drosophila CDG-Ia model. CRISPR-generated pmm2-null Drosophila mutants display severely disrupted glycosylation and early lethality, whereas RNAi-targeted knockdown of neuronal PMM2 results in a strong shift in the abundance of pauci-mannose glycan, progressive incoordination and later lethality, closely paralleling human CDG-Ia symptoms of shortened lifespan, movement impairments and defective neural development. Analyses of the well-characterized Drosophila neuromuscular junction (NMJ) reveal synaptic glycosylation loss accompanied by defects in both structural architecture and functional neurotransmission. NMJ synaptogenesis is driven by intercellular signals that traverse an extracellular synaptomatrix and are co-regulated by glycosylation and matrix metalloproteinases (MMPs). Specifically, trans-synaptic signaling by the Wnt protein Wingless (Wg) depends on the heparan sulfate proteoglycan (HSPG) co-receptor Dally-like protein (Dlp), which is regulated by synaptic MMP activity. Loss of synaptic MMP2, Wg ligand, Dlp co-receptor and downstream trans-synaptic signaling occurs with PMM2 knockdown. Taken together, this Drosophila CDG disease model provides a new avenue for the dissection of cellular and molecular mechanisms underlying neurological impairments and is a means by which to discover and test novel therapeutic treatment strategies.

Two classes of matrix metalloproteinases reciprocally regulate synaptogenesis.

Synaptogenesis requires orchestrated intercellular communication between synaptic partners, with trans-synaptic signals necessarily traversing the extracellular synaptomatrix separating presynaptic and postsynaptic cells. Extracellular matrix metalloproteinases (Mmps) regulated by secreted tissue inhibitors of metalloproteinases (Timps), cleave secreted and membrane-associated targets to sculpt the extracellular environment and modulate intercellular signaling. Here, we test the roles of Mmp at the neuromuscular junction (NMJ) model synapse in the reductionist Drosophila system, which contains just two Mmps (secreted Mmp1 and GPI-anchored Mmp2) and one secreted Timp. We found that all three matrix metalloproteome components co-dependently localize in the synaptomatrix and show that both Mmp1 and Mmp2 independently restrict synapse morphogenesis and functional differentiation. Surprisingly, either dual knockdown or simultaneous inhibition of the two Mmp classes together restores normal synapse development, identifying a reciprocal suppression mechanism. The two Mmp classes co-regulate a Wnt trans-synaptic signaling pathway modulating structural and functional synaptogenesis, including the GPI-anchored heparan sulfate proteoglycan (HSPG) Wnt co-receptor Dally-like protein (Dlp), cognate receptor Frizzled-2 (Frz2) and Wingless (Wg) ligand. Loss of either Mmp1 or Mmp2 reciprocally misregulates Dlp at the synapse, with normal signaling restored by co-removal of both Mmp classes. Correcting Wnt co-receptor Dlp levels in both Mmp mutants prevents structural and functional synaptogenic defects. Taken together, these results identify an Mmp mechanism that fine-tunes HSPG co-receptor function to modulate Wnt signaling to coordinate synapse structural and functional development.

Access of torsinA to the inner nuclear membrane is activity dependent and regulated in the endoplasmic reticulum.

TorsinA (also known as torsin-1A) is a membrane-embedded AAA+ ATPase that has an important role in the nuclear envelope lumen. However, most torsinA is localized in the peripheral endoplasmic reticulum (ER) lumen where it has a slow mobility that is incompatible with free equilibration between ER subdomains. We now find that nuclear-envelope-localized torsinA is present on the inner nuclear membrane (INM) and ask how torsinA reaches this subdomain. The ER system contains two transmembrane proteins, LAP1 and LULL1 (also known as TOR1AIP1 and TOR1AIP2, respectively), that reversibly co-assemble with and activate torsinA. Whereas LAP1 localizes on the INM, we show that LULL1 is in the peripheral ER and does not enter the INM. Paradoxically, interaction between torsinA and LULL1 in the ER targets torsinA to the INM. Native gel electrophoresis reveals torsinA oligomeric complexes that are destabilized by LULL1. Mutations in torsinA or LULL1 that inhibit ATPase activity reduce the access of torsinA to the INM. Furthermore, although LULL1 binds torsinA in the ER lumen, its effect on torsinA localization requires cytosolic-domain-mediated oligomerization. These data suggest that LULL1 oligomerizes to engage and transiently disassemble torsinA oligomers, and is thereby positioned to transduce cytoplasmic signals to the INM through torsinA.

N-glycosylation requirements in neuromuscular synaptogenesis.

Neural development requires N-glycosylation regulation of intercellular signaling, but the requirements in synaptogenesis have not been well tested. All complex and hybrid N-glycosylation requires MGAT1 (UDP-GlcNAc:α-3-D-mannoside-ß1,2-N-acetylglucosaminyl-transferase I) function, and Mgat1 nulls are the most compromised N-glycosylation condition that survive long enough to permit synaptogenesis studies. At the Drosophila neuromuscular junction (NMJ), Mgat1 mutants display selective loss of lectin-defined carbohydrates in the extracellular synaptomatrix, and an accompanying accumulation of the secreted endogenous Mind the gap (MTG) lectin, a key synaptogenesis regulator. Null Mgat1 mutants exhibit strongly overelaborated synaptic structural development, consistent with inhibitory roles for complex/hybrid N-glycans in morphological synaptogenesis, and strengthened functional synapse differentiation, consistent with synaptogenic MTG functions. Synapse molecular composition is surprisingly selectively altered, with decreases in presynaptic active zone Bruchpilot (BRP) and postsynaptic Glutamate receptor subtype B (GLURIIB), but no detectable change in a wide range of other synaptic components. Synaptogenesis is driven by bidirectional trans-synaptic signals that traverse the glycan-rich synaptomatrix, and Mgat1 mutation disrupts both anterograde and retrograde signals, consistent with MTG regulation of trans-synaptic signaling. Downstream of intercellular signaling, pre- and postsynaptic scaffolds are recruited to drive synaptogenesis, and Mgat1 mutants exhibit loss of both classic Discs large 1 (DLG1) and newly defined Lethal (2) giant larvae [L(2)GL] scaffolds. We conclude that MGAT1-dependent N-glycosylation shapes the synaptomatrix carbohydrate environment and endogenous lectin localization within this domain, to modulate retention of trans-synaptic signaling ligands driving synaptic scaffold recruitment during synaptogenesis.

Relative tissue expression of homologous torsinB correlates with the neuronal specific importance of DYT1 dystonia-associated torsinA.

A three base-pair deletion in the widely expressed TOR1A gene causes the childhood onset, neurological disease of DYT1 dystonia. Mouse Tor1a gene knockout also specifically affects the developing nervous system. However, in both cases, the basis of neuronal tissue specificity is unknown. TorsinA is one of four predicted mammalian torsin ATPases associated with assorted cellular activities (AAA+) proteins, raising the possibility that expression of a functionally homologous torsin compensates for torsinA loss in non-neuronal tissues. We find that all four mammalian torsins are endoplasmic reticulum resident glycoproteins. TorsinA, torsinB and torsin2 are all present in large M(r) complexes, which suggests that each assembles into an oligomeric AAA+ enzyme. Introducing a mutation (WB(EQ)) that typically stabilizes AAA+ proteins in a substrate-bound state causes torsinA and torsinB to associate with a shared nuclear envelope (NE) binding partner and this NE localization requires the torsinA interacting protein, lamina associated polypeptide 1. Although torsin proteins are widely expressed in the adult mouse, we identified that embryonic neuronal tissues contain relatively low torsinB levels. Therefore, our results reveal that torsinB expression inversely correlates with the cell and developmental requirement for torsinA. In conclusion, multiple cell types appear to utilize torsin AAA+ proteins and differential expression of torsinB may contribute to both the neuronal specific importance of torsinA and the symptom specificity of DYT1 dystonia.