A case-control study evaluating the unnecessary use of intravenous broad-spectrum antibiotics in presumed sepsis and septic-shock patients in the emergency department.

Objectives: Recognition of sepsis frequently occurs in emergency departments. To evaluate the appropriateness of empiric antibiotic use in the setting of suspected sepsis in emergency department, the percentages of bacterial infection and antibiotic-related adverse drug effects were quantified in an emergency department at an academic medical center. Methods: We retrospectively reviewed electronic medical records of adults who presented to the emergency department between January 2018 and June 2018 with suspected sepsis (defined as having ≥2 systemic inflammatory response syndrome [SIRS] criteria) and received ≥1 dose of intravenous broad-spectrum antibiotic. Results: In total, 218 patients were included in the final analysis. Moreover, 19.3% of these patients had confirmed bacterial infections; 44.5% had suspected bacterial infections; and 35.9% did not have bacterial infection. Elevated SIRS score (ie, ≥2) and Quick Sequential Organ Failure Assessment (qSOFA) score (ie, ≥2) were not associated with the presence of bacterial infections. We identified 90-day Clostridioides difficile infections in 7 patients and drug-resistant organism infections in 6 patients, regardless of the presence of bacterial infections. Conclusions: A high number of patients received intravenous broad-spectrum antibiotics in the emergency department without confirmed or suspected bacterial infections that were supported by microbiologic cultures, radiographic imaging, or other symptoms of infections. Most patients who were initially admitted to the emergency department with suspected sepsis were discharged home after receiving 1 dose of intravenous antibiotic. Patients who were initially screened using SIRS score and who received broad-spectrum antibiotics in the emergency department were without confirmed or suspected bacterial infection.

Angiotensin-(1-7) improves cognitive function and reduces inflammation in mice following mild traumatic brain injury.

Introduction: Traumatic brain injury (TBI) is a leading cause of disability in the US. Angiotensin 1-7 (Ang-1-7), an endogenous peptide, acts at the G protein coupled MAS1 receptors (MASR) to inhibit inflammatory mediators and decrease reactive oxygen species within the CNS. Few studies have identified whether Ang-(1-7) decreases cognitive impairment following closed TBI. This study examined the therapeutic effect of Ang-(1-7) on secondary injury observed in a murine model of mild TBI (mTBI) in a closed skull, single injury model. Materials and methods: Male mice (n = 108) underwent a closed skull, controlled cortical impact injury. Two hours after injury, mice were administered either Ang-(1-7) (n = 12) or vehicle (n = 12), continuing through day 5 post-TBI, and tested for cognitive impairment on days 1-5 and 18. pTau, Tau, GFAP, and serum cytokines were measured at multiple time points. Animals were observed daily for cognition and motor coordination via novel object recognition. Brain sections were stained and evaluated for neuronal injury. Results: Administration of Ang-(1-7) daily for 5 days post-mTBI significantly increased cognitive function as compared to saline control-treated animals. Cortical and hippocampal structures showed less damage in the presence of Ang-(1-7), while Ang-(1-7) administration significantly changed the expression of pTau and GFAP in cortical and hippocampal regions as compared to control. Discussion: These are among the first studies to demonstrate that sustained administration of Ang-(1-7) following a closed-skull, single impact mTBI significantly improves neurologic outcomes, potentially offering a novel therapeutic modality for the prevention of long-term CNS impairment following such injuries.

Effect of Jejunal Administration on Tacrolimus Trough Concentrations in a Pediatric Liver Transplant Recipient.

Maintenance immunosuppression regimens containing calcineurin inhibitors, specifically tacrolimus, are standard of care for rejection prevention in pediatric liver transplantation. Challenges with tacrolimus administration are common with pediatric patients, and guidance for non-oral, enteral administration of tacrolimus is limited. We report the case of an 11-year-old male orthotopic liver transplant recipient with a history of malnutrition requiring a jejunostomy tube (J-tube) for enteral nutrition and medication administration post-transplantation. Tacrolimus was initially given orally, and then transitioned to J-tube administration for 10 days. Tacrolimus trough concentrations declined significantly following conversion to J-tube administration and remained subtherapeutic despite a 3-fold dose increase. Once transitioned back to the oral route, trough concentrations became supratherapeutic requiring dose reductions until goal concentrations were achieved. This case demonstrates reduced bioavailability and need for increased dosing, when tacrolimus is administered through a J-tube.

Increasing Alprostadil Requirements in a Neonate With Cardiac Anomalies and Co-administration of Rectal and Oral Acetaminophen.

A patent ductus arteriosus (PDA) results from the failure of the ductus arteriosus to close within 72 hours after birth. In most neonates, a PDA can lead to significant morbidities and often warrants pharmacologic intervention for closure. Common pharmacologic interventions include indomethacin, ibuprofen, and acetaminophen. In cases of ductal-dependent congenital heart defects (CHDs), such as hypoplastic left heart syndrome, it is imperative to keep the ductus arteriosus patent to maintain adequate pulmonary or systemic circulation until surgical intervention can be performed. The only proven pharmacologic agent used for this indication is prostaglandin E1 (PGE1) commonly in the form of intravenous alprostadil. This case report describes a neonate with multiple cardiac and genetic anomalies that required increased alprostadil infusion after exposure to rectal and oral acetaminophen. The patient initially presented with a large PDA on echocardiogram (ECHO); however, after an incidental finding of a small PDA on ECHO, the administration of as needed rectal acetaminophen was discontinued out of concern for its effects on patency. After a few days of increased prostaglandin therapy and 2 reassuring ECHO results, the patient was given oral acetaminophen on an as needed basis. Within 24 hours of restarting the acetaminophen, the repeated ECHO showed a reduction in PDA and flow. In patients with ductal-dependent cardiac lesions, it is important to maintain PDA patency and, therefore, introducing a medication with antiprostaglandin properties should be avoided.

Therapeutic Options for Coronavirus Disease 2019 (COVID-19): Where Are We Now?

PURPOSE OF REVIEW: Rapidly evolving treatment paradigms of coronavirus disease 2019 (COVID-19) introduce challenges for clinicians to keep up with the pace of published literature and to critically appraise the voluminous data produced. This review summarizes the clinical evidence from key studies examining the place of therapy of recommended drugs and management strategies for COVID-19. RECENT FINDINGS: The global magnitude and duration of the pandemic have resulted in a flurry of interventional treatment trials evaluating both novel and repurposed drugs targeting various aspects of the viral life cycle. Additionally, clinical observations have documented various stages or phases of COVID-19 and underscored the importance of timing for the efficacy of studied therapies. Since the start of the COVID-19 pandemic, many observational, retrospective, and randomized controlled studies have been conducted to guide management of COVID-19 using drug therapies and other management strategies. Large, randomized, or adaptive platform trials have proven the most informative to guide recommended treatments to-date. Antimicrobial stewardship programs can play a pivotal role in ensuring appropriate use of COVID-19 therapies based on evolving clinical data and limiting unnecessary antibiotics given low rates of co-infection. SUMMARY: Given the rapidly evolving medical literature and treatment paradigms, it is recommended to reference continuously updated, curated guidelines from national and international sources. While the drugs and management strategies mentioned in this review represent the current state of recommendations, many therapies are still under investigation to further define optimal COVID-19 treatment. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s11908-021-00769-8.

Chemotherapy-Induced Peripheral Neuropathy: Mechanisms and Therapeutic Avenues.

Chemotherapy-induced peripheral neuropathy (CIPN) is a serious and often persistent adverse consequence of certain chemotherapeutic agents. It is a major dose-limiting factor of many first-line chemotherapies, affecting 20-50% of patients at standard doses and nearly all patients at high doses. As cancer survivorship continues to increase with improvements in early diagnosis and treatment, more patients will experience CIPN despite completing cancer treatment, which interferes with recovery, leading to chronic pain and worsening quality of life. The National Cancer Institute has identified CIPN as a priority in translational research. To date, there are no FDA-approved drugs for preventing or treating CIPN, with emerging debate on mechanisms and promising new targets. This review highlights current literature and suggests novel approaches to CIPN based on proposed mechanisms of action that aim either to confer neuroprotection against chemotherapy-induced neurotoxicity or reverse the downstream effects of painful neuropathy.

Patency of arterial repairs from wartime extremity vascular injuries.

BACKGROUND: Extremity vascular injury (EVI) causes significant disability in Veterans of the Afghanistan/Iraq conflicts. Advancements in acute trauma care improved survival and decreased amputations. The study of wartime EVI has relied on successful limb salvage as a surrogate for vascular repair. We used imaging studies as a specific measure of arterial repair durability. METHODS: Service members with EVI were identified using the Department of Defense Trauma Registry and validated by chart abstraction. Inclusion criteria for the arterial patency subgroup included an initial repair attempt with subsequent imaging reports (duplex ultrasound, CT angiography, and angiogram) documenting initial patency. RESULTS: The cohort of 527 included 140 Veterans with available imaging studies for 143 arterial repairs; median follow-up from injury time to last available imaging study was 19 months (Q1-Q3: 3-58; range: 1-175). Injury mechanism was predominantly explosions (52%) and gunshot wounds (42%). Of the 143 arterial repairs, 81% were vein grafts. Eight repairs were occluded, replaced or included in extremity amputations. One upper extremity and three transtibial late amputations were performed for chronic pain and poor function averaging 27 months (SD: 4; range: 24-32). Kaplan-Meier analysis estimated patency rates of 99%, 97%, 95%, 91% and 91% at 3, 6, 12, 24, and 36 months, respectively, with similar results for upper and lower extremity repairs. Explosive and gunshot wound injury mechanisms had similar patency rates and upper extremity injuries repaired with vein grafts had increased patency. CONCLUSIONS: Arterial repair mid-term patency in combat-related extremity injuries is excellent based on imaging studies for 143 repairs. Assertive attempts at acute limb salvage and vascular repair are justified with decisions for amputation versus limb salvage based on the overall condition of the patient and degree of concomitant nerve, orthopedic and soft tissue injuries rather than the presence of arterial injuries. LEVEL OF EVIDENCE: Therapeutic/care management, level IV.

Propranolol attenuates cognitive, learning, and memory deficits in a murine model of traumatic brain injury.

BACKGROUND: ß-blockers have been shown to improve survival after traumatic brain injury (TBI); however, the impact of continuous dosage of ß-blockers on cognitive function has not been elucidated. We hypothesized that a daily dose of propranolol can improve memory, learning, and cognitive function following TBI. STUDY DESIGN: Twenty male C57BL mice were subjected to a cortical-controlled moderate TBI. Two hours after TBI, animals were randomly allocated to either the ß-blocker group (n = 10) or the placebo group (n = 10). Mice in the ß-blocker group received intraperitoneal 4 mg/kg propranolol every 24 hours for 7 days while the placebo group received 4 mg/kg normal saline. Baseline novel object recognition and classic maze tests were done prior to TBI and then daily from Day 1 through 7 after TBI. Animals were sacrificed on Day 7. Serum biomarkers were measured using ELISA and brain sections were analyzed using western blot and hematoxylin and eosin staining. RESULTS: Both the ß-blocker and placebo groups had lower recognition index scores compared with the baseline following TBI. ß-blocker mice had significantly higher novel object recognition scores compared with placebo mice 2 days after TBI. The ß-blocker group required less time to complete the maze-test compared to placebo group after Day 4. There was no difference regarding the serum levels of IL-1ß, IL-6, and TNF-α. The ß-blocker group had lower levels of UCHL-1 and higher levels of Hsp-70 in brain lysate. Hematoxylin and eosin staining revealed that more neurons in the hippocampal-CA1 area underwent apoptosis in the placebo group compared with the ß-blocker group. CONCLUSION: Postinjury propranolol administration results in improved memory, learning and cognitive functions in a murine model of moderate TBI. Propranolol increases the expression of antiapoptotic protein (Hsp-70) and decreases cell death in the hippocampal-CA1 area compared with the placebo.

Carotid Artery Angioplasty and Stenting for Atherosclerotic Plaque with Mobile Intimal Flap.

Atherosclerotic carotid stenosis associated with a mobile carotid plaque (MCP) is a relatively rare entity, observed in less than 1 in 2,000 carotid ultrasound examinations. As such, the natural history of this lesion and risk for neurological thromboembolic complications are not well defined. Small case reports have described treatment varying from medical management with anticoagulation, to carotid endarterectomy, and more recently, carotid stenting. We present two patients with carotid stenosis associated with a MCP. A distinct MCP component that varied with the cardiac cycle was clearly delineated on ultrasound in both patients. Intravascular ultrasound (IVUS) at the time of carotid stenting confirmed the MCP. Successful carotid angioplasty and stenting was performed in both patients with resolution of the MCP documented on IVUS and follow-up duplex ultrasound. Although the definitive treatment method remains uncertain, carotid stenting is a viable option for treatment in patients with MCPs.

Cryopreserved venous allograft is an acceptable conduit in patients with current or prior angioaccess graft infection.

OBJECTIVE: The durability of cryopreserved allograft has been previously demonstrated in the setting of infection. The objective of this study was to examine the safety, efficacy, patency, and cost per day of graft patency associated with using cryopreserved allograft (vein and artery) for hemodialysis access in patients with no autogenous tissue for native fistula creation and with arteriovenous graft infection or in patients at high risk for infection. METHODS: Patients implanted with cryopreserved allograft for hemodialysis access between January 2004 and January 2014 were reviewed using a standardized, multi-institutional database that evaluated demographic, comorbidity, procedural, and outcomes data. RESULTS: There were 457 patients who underwent placement of cryopreserved vein (femoral: n = 337, saphenous: n = 11) or artery (femoral: n = 109) for hemodialysis access at 20 hospitals. Primary indications for allograft use included high risk of infection in 191 patients (42%), history of infected prosthetic graft in 169 (37%), and current infection in 97 (21%). Grafts were placed more frequently in the arm (78%) than in the groin, with no difference in allograft conduit used. Mean time from placement to first hemodialysis use was 46 days (median, 34 days). Duration of functional graft use was 40 ± 7 months for cryopreserved vein and 21 ± 8 months for cryopreserved artery (P < .05), and mean number of procedures required to maintain patency at follow-up of 58 ± 21 months was 1.6 for artery and 0.9 for vein (P < .05). Local access complications occurred in 32% of patients and included late thrombosis (14%), graft stenosis (9%), late infection (9%), arteriovenous access malfunction (7%), early thrombosis (3%), and early infection (3%). Early and late infections both occurred more frequently in the groin (P = .030, P = .017, respectively), and late thrombosis occurred more frequently with cryopreserved artery (P < .001). Of the 82 patients (18%) in whom the cryopreserved allograft was placed in the same location as the excised infected prosthetic graft, 13 had infection of the allograft during the study period (early: n = 4; late: n = 9), with no significant difference in infection rate (P = .312) compared with the remainder of the study population. The 1-, 3-, and 5-year primary patency was 58%, 35%, and 17% for cryopreserved femoral vein and 49%, 17%, and 8% for artery, respectively (P < .001). Secondary patency at 1, 3, and 5 years was 90%, 78%, and 58% for cryopreserved femoral vein and 75%, 53%, and 42% for artery, respectively (P < .001). Mean allograft fee per day of graft patency was $4.78 for cryopreserved vein and $6.97 for artery (P < .05), excluding interventional costs to maintain patency. CONCLUSIONS: Cryopreserved allograft provides an excellent conduit for angioaccess when autogenous tissue is not available in patients with current or past conduit infection. Cryopreserved vein was associated with higher patency and a lower cost per day of graft patency. Cryopreserved allograft allows for immediate reconstruction through areas of infection, reduces the need for staged procedures, and allows early use for dialysis.

Endovascular Repair of Concomitant Celiac and Splenic Artery Aneurysms Using a Combination of Coil Embolization and Aortic Cuff Stent Graft.

Large celiac artery aneurysms are associated with a high rupture and mortality risk. Traditionally, open surgical repair has been the mainstay of treatment. Endovascular alternatives have been increasingly described, ranging from coil embolization to exclusion with covered stent grafts. Certain features such as a short wide neck, small vessel diameters, and severe vessel tortuosity can limit these two options. We describe a 75-year-old man with a splenic and celiac trunk aneurysm that was treated using a combination of coil embolization to occlude the outflow artery and aneurysm sac, followed by an aortic stent graft cuff to block the inflow. This resulted in successful exclusion of the splenic and celiac artery aneurysms while preserving flow to both the spleen and liver through collateral pathways.

Trauma experts versus pediatric experts: comparison of outcomes in pediatric penetrating injuries.

BACKGROUND: While pediatric trauma centers (PTCs) can uniquely care for pediatric patients, adult trauma centers (ATCs) may be more accessible. Evidence is scarce regarding outcomes of pediatric patients with penetrating trauma treated at PTCs versus ATCs. MATERIALS AND METHODS: We performed a retrospective study using the National Trauma Data Bank to identify pediatric patients aged ≤18 y with penetrating injuries from 2007 to 2012, treated at stand-alone PTCs or ATCs. We excluded patients treated at combined PTC or ATC, transferred between hospitals, with gunshot wounds (GSW) to the head, or dead on arrival. Eligible patients numbered 26,276 (PTC, n = 3737; ATC, n = 22,539). The primary outcome was in-hospital mortality. The secondary outcome was discharge location as a potential surrogate for functional outcome. Univariate and multivariate analyses assessed trauma center type as an independent risk factor for outcomes. RESULTS: Patients treated at ATCs were more likely to have Injury Severity Score >15, Glasgow Coma Scale <9, GSW, cardiovascular injuries, and emergent operations (P < 0.001). Adjusted odds ratios (ORs) for mortality favored PTCs but without statistical significance (OR, 0.592; P = 0.054). In subgroup analyses, children with aged ≤12 y, those with GSW injury mechanism, and those who underwent emergent operations at PTCs were more frequently discharged home versus elsewhere (OR, 0.327, 0.483, and 0.394; P values <0.001, <0.001, and 0.004, respectively). CONCLUSIONS: Children with penetrating injuries demonstrated equivalent survival outcomes whether they were treated at PTCs or ATCs. Younger pediatric patients may have superior functional outcomes when treated at PTCs.

Postoperative antibiotic use and the incidence of intra-abdominal abscess in the setting of suppurative appendicitis: a retrospective analysis.

BACKGROUND: Although guidelines exist for postoperative antibiotic use in acute appendicitis that is perforated, gangrenous, or simple/uncomplicated, there are less data about its use in suppurative appendicitis. Here, we targeted this subgroup of patients to determine whether postoperative antibiotic administration affects incidence of intra-abdominal abscess formation. METHODS: We retrospectively examined 1,192 patients who underwent laparoscopic appendectomy for acute appendicitis at Kaiser Permanente Fontana Hospital between August 2010 and August 2013. Suppurative appendicitis was described for 143 (12%) patients. Fifty-two patients received postoperative antibiotics for at least 1 week on discharge home, 91 did not. RESULTS: Of 143 patients with suppurative appendicitis, 1 (1.9%) who received postoperative antibiotics came back with an intra-abdominal abscess within 1 month. Of the 91 patients in the no antibiotic group, 1 (1.1%) came back with an intra-abdominal abscess. CONCLUSIONS: The administration of postoperative antibiotic in the setting of suppurative appendicitis has no effect on the rate of intra-abdominal abscess formation. Routine postoperative antibiotics may not be necessary in this patient population, and more evidence is needed to justify its use.

A rare case of concurrent signet-ring carcinoma of breast and microangiopathic hemolytic anemia.

Microangiopathic hemolytic anemia (MAHA) can be an uncommon presentation of an underlying malignancy, most often due to signet-ring cell carcinoma (SRCC). Additionally, pure SRCC in a breast primary-tumor comprises <2% of all breast cancers (Shin SY, Park H, Chae SW, Woo HY. Microangiopathic hemolytic anemia as the first manifestation of metastatic signet-ring cell carcinoma of unknown origin: a case report and review of literature. Kor J Lab Med 2011;31:157-61). To the best of our knowledge, the combination of these two entities, pure breast primary SRCC along with MAHA, has not been reported. Here, we present such a rare case. We also evaluate the current literature regarding this and similar disease processes, of which evidence is scarce and further research is needed.

Disruption of the abdominal-B promoter tethering element results in a loss of long-range enhancer-directed Hox gene expression in Drosophila.

There are many examples within gene complexes of transcriptional enhancers interacting with only a subset of target promoters. A number of molecular mechanisms including promoter competition, insulators and chromatin looping are thought to play a role in regulating these interactions. At the Drosophila bithorax complex (BX-C), the IAB5 enhancer specifically drives gene expression only from the Abdominal-B (Abd-B) promoter, even though the enhancer and promoter are 55 kb apart and are separated by at least three insulators. In previous studies, we discovered that a 255 bp cis-regulatory module, the promoter tethering element (PTE), located 5' of the Abd-B transcriptional start site is able to tether IAB5 to the Abd-B promoter in transgenic embryo assays. In this study we examine the functional role of the PTE at the endogenous BX-C using transposon-mediated mutagenesis. Disruption of the PTE by P element insertion results in a loss of enhancer-directed Abd-B expression during embryonic development and a homeotic transformation of abdominal segments. A partial deletion of the PTE and neighboring upstream genomic sequences by imprecise excision of the P element also results in a similar loss of Abd-B expression in embryos. These results demonstrate that the PTE is an essential component of the regulatory network at the BX-C and is required in vivo to mediate specific long-range enhancer-promoter interactions.

Functional evolution of cis-regulatory modules at a homeotic gene in Drosophila.

It is a long-held belief in evolutionary biology that the rate of molecular evolution for a given DNA sequence is inversely related to the level of functional constraint. This belief holds true for the protein-coding homeotic (Hox) genes originally discovered in Drosophila melanogaster. Expression of the Hox genes in Drosophila embryos is essential for body patterning and is controlled by an extensive array of cis-regulatory modules (CRMs). How the regulatory modules functionally evolve in different species is not clear. A comparison of the CRMs for the Abdominal-B gene from different Drosophila species reveals relatively low levels of overall sequence conservation. However, embryonic enhancer CRMs from other Drosophila species direct transgenic reporter gene expression in the same spatial and temporal patterns during development as their D. melanogaster orthologs. Bioinformatic analysis reveals the presence of short conserved sequences within defined CRMs, representing gap and pair-rule transcription factor binding sites. One predicted binding site for the gap transcription factor KRUPPEL in the IAB5 CRM was found to be altered in Superabdominal (Sab) mutations. In Sab mutant flies, the third abdominal segment is transformed into a copy of the fifth abdominal segment. A model for KRUPPEL-mediated repression at this binding site is presented. These findings challenge our current understanding of the relationship between sequence evolution at the molecular level and functional activity of a CRM. While the overall sequence conservation at Drosophila CRMs is not distinctive from neighboring genomic regions, functionally critical transcription factor binding sites within embryonic enhancer CRMs are highly conserved. These results have implications for understanding mechanisms of gene expression during embryonic development, enhancer function, and the molecular evolution of eukaryotic regulatory modules.

A novel promoter-tethering element regulates enhancer-driven gene expression at the bithorax complex in the Drosophila embryo.

A key question in our understanding of the cis-regulation of gene expression during embryonic development has been the molecular mechanism that directs enhancers to specific promoters within a gene complex. Promoter competition and insulators are thought to play a role in regulating these interactions. In the bithorax complex of Drosophila, the IAB5 enhancer is located 55 kb 3' of the Abdominal-B (Abd-B) promoter and 48 kb 5' of the abdominal-A (abd-A) promoter. Although roughly equidistant from the two promoters, IAB5 specifically interacts only with the Abdominal-B promoter, even though the enhancer and promoter are separated by at least two insulators. Here we demonstrate that a 255 bp element, located 40 bp 5' of the Abd-B transcriptional start site, has a novel cis-regulatory activity as it is able to tether IAB5 to the Abd-B promoter in transgenic embryos. The tethering element is sufficient to direct IAB5 to an ectopic promoter in competition assays. Deletion of the promoter-tethering element results in the redirection of enhancer-driven gene expression on transgenes. Taken together, these results provide evidence that specific long-range enhancer-promoter interactions in the bithorax complex are regulated by a tethering element 5' of the Abd-B promoter. We discuss a bioinformatic analysis of the tethering element across different Drosophila species and a possible molecular mechanism by which this element functions. We also examine existing evidence that this novel class of cis-regulatory elements might regulate enhancer-promoter specificity at other gene complexes.

The abdominal-B promoter tethering element mediates promoter-enhancer specificity at the Drosophila bithorax complex.

At the Drosophila bithorax complex many distinct classes of cis-regulatory modules work collectively during development to control gene expression. Abdominal-B (Abd-B) is one of three homeotic genes in the BX-C and is expressed in specific presumptive abdominal segments in the embryo. The transcription of Abd-B is tightly controlled by an array of cis-regulatory modules that direct its expression over extended genomic distances. These regulatory modules include promoters, insulators, silencers, enhancers, promoter targeting sequences and the recently identified promoter tethering element (PTE). To activate gene expression at the endogenous complex, enhancers located >50 kb away must bypass intervening insulators to interact with the Abd-B promoter. The molecular mechanisms that allow enhancers to bypass insulators are not currently well understood. In this short article, we report on a novel mechanism for insulator bypass involving the PTE. In addition, we use bioinformatic analysis across twelve Drosophila genomes to identify putative cis-regulatory sequences that may be capable of facilitating specific promoter-enhancer interactions at the bithorax complex and propose a model for their molecular function during development.

The human and mouse H19 imprinting control regions harbor an evolutionarily conserved silencer element that functions on transgenes in Drosophila.

Differentially methylated regions have been characterized at a number of imprinted gene complexes with important roles in the regulation of monoallelic expression of one or more genes. The differentially methylated imprinting control region (ICR) located upstream of the murine H19 gene has been shown to control the imprinted expression of H19 and the coordinately regulated Igf2 gene by acting as a transcriptional silencer. In this study, we show that the murine ICR maintains this function when tested in an in vivo transgenic Drosophila assay in the absence of DNA methylation. Furthermore, the H19 ICR interacts distinctively with Drosophila promoters of different regulatory strengths. We also demonstrate that the comparable region upstream of the human H19 gene is a multipartite cis-regulatory element, demonstrating silencing function when tested in mammalian and Drosophila systems. These results indicate a conservation of the H19/Igf2 imprinting mechanism between humans and mice and further elucidate the functional activities of the H19 ICR. They demonstrate the value of Drosophila as an in vivo system for testing function and interaction of eukaryotic regulatory elements and that mechanisms of transcriptional cis-regulation in mammals and Drosophila are conserved.