Acinetobacter type VI secretion system comprises a non-canonical membrane complex.

A. baumannii can rapidly acquire new resistance mechanisms and persist on abiotic surface, enabling the colonization of asymptomatic human host. In Acinetobacter the type VI secretion system (T6SS) is involved in twitching, surface motility and is used for interbacterial competition allowing the bacteria to uptake DNA. A. baumannii possesses a T6SS that has been well studied for its regulation and specific activity, but little is known concerning its assembly and architecture. The T6SS nanomachine is built from three architectural sub-complexes. Unlike the baseplate (BP) and the tail-tube complex (TTC), which are inherited from bacteriophages, the membrane complex (MC) originates from bacteria. The MC is the most external part of the T6SS and, as such, is subjected to evolution and adaptation. One unanswered question on the MC is how such a gigantesque molecular edifice is inserted and crosses the bacterial cell envelope. The A. baumannii MC lacks an essential component, the TssJ lipoprotein, which anchors the MC to the outer membrane. In this work, we studied how A. baumannii compensates the absence of a TssJ. We have characterized for the first time the A. baumannii's specific T6SS MC, its unique characteristic, its membrane localization, and assembly dynamics. We also defined its composition, demonstrating that its biogenesis employs three Acinetobacter-specific envelope-associated proteins that define an intricate network leading to the assembly of a five-proteins membrane super-complex. Our data suggest that A. baumannii has divided the function of TssJ by (1) co-opting a new protein TsmK that stabilizes the MC and by (2) evolving a new domain in TssM for homo-oligomerization, a prerequisite to build the T6SS channel. We believe that the atypical species-specific features we report in this study will have profound implication in our understanding of the assembly and evolutionary diversity of different T6SSs, that warrants future investigation.

Reducing length of stay after transfemoral transcatheter aortic valve implantation: the FAST-TAVI II trial.

BACKGROUND AND AIMS: The length of stay (LOS) after transcatheter aortic valve implantation (TAVI) remains extremely variable whereas early discharge has been shown to be feasible and safe. The study objective was to evaluate the efficacy and safety of an intervention aimed at reducing LOS after transfemoral TAVI. METHODS: FAST-TAVI II is a prospective, multicentre, cluster, randomized, controlled study including patients with severe symptomatic aortic stenosis, who had transfemoral TAVI. The intervention consisted in a dedicated training programme to implement 10 quality of care measures to reduce LOS with an implementation phase of eight weeks. The primary endpoint was the proportion of patients discharged early within 3 days. Secondary endpoints included: LOS, 30-day mortality and 30-day incidence of readmission for cardiovascular events. RESULTS: During the study period, 969 patients were enrolled in the intervention group and 860 patients in the control group. Mean age was 81.9 ± 6.6 years and mean EuroSCORE II was 4.4 ± 4.5%. Early discharge was achieved in 563 (58.1%) patients in the intervention group vs. 364 (42.3%) patients in the control group (P < .0001). Median LOS was significantly reduced in the intervention group compared to the control group [3 (IQR: 3) vs. 4 days (IQR: 3), P < .0001]. Thirty-day mortality was low and similar in the two groups (0.5% vs. 0.9%, P = .30), as were 30-day readmissions (4.6% vs. 2.8%, P = .28). CONCLUSIONS: The intervention was simple and fast to implement, and was effective and safe to reduce LOS and increase the proportion of patients discharged early after TAVI (NCT04503655).

A streamlined pathway for transcatheter aortic valve implantation: the BENCHMARK study.

BACKGROUND AND AIMS: There is significant potential to streamline the clinical pathway for patients undergoing transcatheter aortic valve implantation (TAVI). The purpose of this study was to evaluate the effect of implementing BENCHMARK best practices on the efficiency and safety of TAVI in 28 sites in 7 European countries. METHODS: This was a study of patients with severe symptomatic aortic stenosis (AS) undergoing TAVI with balloon-expandable valves before and after implementation of BENCHMARK best practices. Principal objectives were to reduce hospital length of stay (LoS) and duration of intensive care stay. Secondary objective was to document patient safety. RESULTS: Between January 2020 and March 2023, 897 patients were documented prior to and 1491 patients after the implementation of BENCHMARK practices. Patient characteristics were consistent with a known older TAVI population and only minor differences. Mean LoS was reduced from 7.7 ± 7.0 to 5.8 ± 5.6 days (median 6 vs. 4 days; P < .001). Duration of intensive care was reduced from 1.8 to 1.3 days (median 1.1 vs. 0.9 days; P < .001). Adoption of peri-procedure best practices led to increased use of local anaesthesia (96.1% vs. 84.3%; P < .001) and decreased procedure (median 47 vs. 60 min; P < .001) and intervention times (85 vs. 95 min; P < .001). Thirty-day patient safety did not appear to be compromised with no differences in all-cause mortality (0.6% in both groups combined), stroke/transient ischaemic attack (1.4%), life-threatening bleeding (1.3%), stage 2/3 acute kidney injury (0.7%), and valve-related readmission (1.2%). CONCLUSIONS: Broad implementation of BENCHMARK practices contributes to improving efficiency of TAVI pathway reducing LoS and costs without compromising patient safety.

Infective Endocarditis After Transcatheter Versus Surgical Aortic Valve Replacement.

BACKGROUND: Scarce data are available comparing infective endocarditis (IE) following surgical aortic valve replacement (SAVR) and transcatheter aortic valve replacement (TAVR). This study aimed to compare the clinical presentation, microbiological profile, management, and outcomes of IE after SAVR versus TAVR. METHODS: Data were collected from the "Infectious Endocarditis after TAVR International" (enrollment from 2005 to 2020) and the "International Collaboration on Endocarditis" (enrollment from 2000 to 2012) registries. Only patients with an IE affecting the aortic valve prosthesis were included. A 1:1 paired matching approach was used to compare patients with TAVR and SAVR. RESULTS: A total of 1688 patients were included. Of them, 602 (35.7%) had a surgical bioprosthesis (SB), 666 (39.5%) a mechanical prosthesis, 70 (4.2%) a homograft, and 350 (20.7%) a transcatheter heart valve. In the SAVR versus TAVR matched population, the rate of new moderate or severe aortic regurgitation was higher in the SB group (43.4% vs 13.5%; P < .001), and fewer vegetations were diagnosed in the SB group (62.5% vs 82%; P < .001). Patients with an SB had a higher rate of perivalvular extension (47.9% vs 27%; P < .001) and Staphylococcus aureus was less common in this group (13.4% vs 22%; P = .033). Despite a higher rate of surgery in patients with SB (44.4% vs 27.3%; P < .001), 1-year mortality was similar (SB: 46.5%; TAVR: 44.8%; log-rank P = .697). CONCLUSIONS: Clinical presentation, type of causative microorganism, and treatment differed between patients with an IE located on SB compared with TAVR. Despite these differences, both groups exhibited high and similar mortality at 1-year follow-up.

Structural basis for loading and inhibition of a bacterial T6SS phospholipase effector by the VgrG spike.

The bacterial type VI secretion system (T6SS) is a macromolecular machine that injects effectors into prokaryotic and eukaryotic cells. The mode of action of the T6SS is similar to contractile phages: the contraction of a sheath structure pushes a tube topped by a spike into target cells. Effectors are loaded onto the spike or confined into the tube. In enteroaggregative Escherichia coli, the Tle1 phospholipase binds the C-terminal extension of the VgrG trimeric spike. Here, we purify the VgrG-Tle1 complex and show that a VgrG trimer binds three Tle1 monomers and inhibits their activity. Using covalent cross-linking coupled to high-resolution mass spectrometry, we provide information on the sites of contact and further identify the requirement for a Tle1 N-terminal secretion sequence in complex formation. Finally, we report the 2.6-Å-resolution cryo-electron microscopy tri-dimensional structure of the (VgrG)3 -(Tle1)3 complex revealing how the effector binds its cargo, and how VgrG inhibits Tle1 phospholipase activity. The inhibition of Tle1 phospholipase activity once bound to VgrG suggests that Tle1 dissociation from VgrG is required upon delivery.

Incidence, Clinical Characteristics, and Impact of Absent Echocardiographic Signs in Patients With Infective Endocarditis After Transcatheter Aortic Valve Implantation.

BACKGROUND: Echocardiography is the primary imaging modality for diagnosis of infective endocarditis (IE) in prosthetic valve endocarditis (PVE) including IE after transcatheter aortic valve implantation (TAVI). This study aimed to evaluate the characteristics and clinical outcomes of patients with absent compared with evident echocardiographic signs of TAVI-IE. METHODS: Patients with definite TAVI-IE derived from the Infectious Endocarditis after TAVI International Registry were investigated comparing those with absent and evident echocardiographic signs of IE defined as vegetation, abscess, pseudo-aneurysm, intracardiac fistula, or valvular perforation or aneurysm. RESULTS: Among 578 patients, 87 (15.1%) and 491 (84.9%) had absent (IE-neg) and evident (IE-pos) echocardiographic signs of IE, respectively. IE-neg were more often treated via a transfemoral access with a self-expanding device and had higher rates of peri-interventional complications (eg, stroke, major vascular complications) during the TAVI procedure (P < .05 for all). IE-neg had higher rates of IE caused by Staphylococcus aureus (33.7% vs 23.2%; P = .038) and enterococci (37.2% vs 23.8%; P = .009) but lower rates of coagulase-negative staphylococci (4.7% vs 20.0%, P = .001). IE-neg was associated with the same dismal prognosis for in-hospital mortality in a multivariate binary regression analysis (odds ratio: 1.51; 95% confidence interval [CI]: .55-4.12) as well as a for 1-year mortality in Cox regression analysis (hazard ratio: 1.10; 95% CI: .67-1.80). CONCLUSIONS: Even with negative echocardiographic imaging, patients who have undergone TAVI and presenting with positive blood cultures and symptoms of infection are a high-risk patient group having a reasonable suspicion of IE and the need for an early treatment initiation.

In situ and high-resolution cryo-EM structure of a bacterial type VI secretion system membrane complex.

Bacteria have evolved macromolecular machineries that secrete effectors and toxins to survive and thrive in diverse environments. The type VI secretion system (T6SS) is a contractile machine that is related to Myoviridae phages. It is composed of a phage tail-like structure inserted in the bacterial cell envelope by a membrane complex (MC) comprising the TssJ, TssL and TssM proteins. We previously reported the low-resolution negative-stain electron microscopy structure of the enteroaggregative Escherichia coli MC and proposed a rotational 5-fold symmetry with a TssJ:TssL:TssM stoichiometry of 2:2:2. Here, cryo-electron tomography analyses of the T6SS MC confirm the 5-fold symmetry in situ and identify the regions of the structure that insert into the bacterial membranes. A high-resolution model obtained by single-particle cryo-electron microscopy highlights new features: five additional copies of TssJ, yielding a TssJ:TssL:TssM stoichiometry of 3:2:2, an 11-residue loop in TssM, protruding inside the lumen of the MC and constituting a functionally important periplasmic gate, and hinge regions. Based on these data, we propose an updated model on MC structure and dynamics during T6SS assembly and function.

CT annulus sizing prior to transcatheter aortic valve replacement (TAVR): evaluation of free-breathing versus breath-holding acquisition.

OBJECTIVES: To assess feasibility and accuracy of aortic annulus measurements using cardiac computed tomography angiography (CTA) performed during free-breathing prior to transcatheter aortic valve replacement (TAVR). MATERIALS AND METHODS: Sixty consecutive TAVR candidates underwent free-breathing wide-detector cardiac CTA, followed by a percutaneous valve replacement. For each, a theoretical valve size was suggested through CT measurements of the annulus, then compared to the size of the actual implanted transcatheter heart valve (THV). The procedural success and the 30-day outcomes were collected. Image quality of the annulus was also studied according to subjective and objective criteria. Data of a control group of 60 patients previously evaluated on breath-holding were also evaluated. RESULTS: A total of 120 patients (mean age, 83 years ± 7, 60 men) were evaluated. All CT acquisitions provided sufficient image quality allowing precise annulus measurements. Mean attenuation (p < 0.001) and image noise (p = 0.01) were higher in the free-breathing group, while image quality was comparable (p = 0.36). The agreement rate between CT-suggested valve size and THV implanted size was comparable, estimated at 87% (κ = 0.79, 95%CI 0.566, 0.908) on free-breathing vs. 82% (κ = 0.78, 95%CI 0.634, 0.904) on breath-holding. The procedure was successful for all patients without increase in 30-day mortality or adverse events. CONCLUSIONS: Free-breathing cardiac CTA allows accurate aortic annulus measurements without compromising image quality or patients' outcome after TAVR. Elderly patients experiencing dyspnea, discomfort, or hearing loss that could prevent proper breath-holding should not be excluded from CT prior to TAVR. CLINICAL RELEVANCE STATEMENT: To decrease elderly patients' discomfort, MDCT evaluation prior to transcatheter aortic valve replacement (TAVR) may be performed on quiet breathing with no significant impact on the outcome. KEY POINTS: • Adhering to CT breathing commands can be challenging for patients with dyspnea, hearing impairment, agitation, or pulmonary diseases. • Free-breathing cardiac CT may be an alternative to breath-holding for patients unable to follow the breathing commands. • Wide-detector CT acquisition on free-breathing does not impair annulus measurements and prosthesis sizing in patients scheduled for TAVR.

Trends in aortic valve replacement for aortic stenosis: a French nationwide study.

AIMS: Transcatheter aortic valve replacement (TAVR) as an alternative to surgical aortic valve replacement (SAVR) has profoundly changed the management of patients with aortic valve stenosis (AS). Large unbiased nationwide data regarding TAVR implementation, impact on SAVR and their respective outcomes are scarce. METHODS AND RESULTS: Based on a French administrative hospital-discharge database, we collected data on all consecutive aortic valve replacements (AVRs) performed in France for AS between 2007 and 2019 [106 253 isolated SAVR (49%), 46 514 combined SAVR (21%), and 65 651 TAVR (30%)]. The number of AVR linearly increased between 2007 and 2019 (from 10 892 to 23 109, P for trend < 0.0001) due to a marked increase in TAVR (from 253 to 13 030, P for trend < 0.0001), while SAVR increased up to 2013 and then declined (10 892 in 2007, 12 699 in 2013, and 10 079 in 2019). The Charlson index decreased linearly for TAVR, but in two steps for SAVR (2011 and 2017). In-hospital mortality rates of both SAVR and TAVR declined (both P for trend < 0.0001) and were similar or lower for TAVR than for isolated SAVR in patients 75 years or above in the last 3 years (2017-19). Complication rates of TAVR also declined but permanent pacemaker rates remained high and length of stay substantial (16.7% and median 6 days, respectively, in 2017-19). CONCLUSION: The number of AVR has doubled in a decade and TAVR has become the dominant form of AVR in 2018. The improvement in patient profiles seems to have anticipated the demonstrated benefit of TAVR in intermediate and low-risk patients. In patients 75 years or older, TAVR should be considered as the first option. We also highlight two important areas for improvement, the high permanent pacemaker rates, and the long length of stay even in the contemporary era. Our results may have major implications for clinical practice and policymakers.

Trends in aortic valve replacement for aortic stenosis: a French nationwide study.

AIMS: Transcatheter aortic valve replacement (TAVR) as an alternative to surgical aortic valve replacement (SAVR) has profoundly changed the management of patients with aortic valve stenosis (AS). Large unbiased nationwide data regarding TAVR implementation, impact on SAVR and their respective outcomes are scarce. METHODS AND RESULTS: Based on a French administrative hospital-discharge database, we collected data on all consecutive aortic valve replacements (AVRs) performed in France for AS between 2007 and 2019 [106 253 isolated SAVR (49%), 46 514 combined SAVR (21%), and 65 651 TAVR (30%)]. The number of AVR linearly increased between 2007 and 2019 (from 10 892 to 23 109, P for trend < 0.0001) due to a marked increase in TAVR (from 253 to 13 030, P for trend < 0.0001), while SAVR increased up to 2013 and then declined (10 892 in 2007, 12 699 in 2013, and 10 079 in 2019). The Charlson index decreased linearly for TAVR, but in two steps for SAVR (2011 and 2017). In-hospital mortality rates of both SAVR and TAVR declined (both P for trend < 0.0001) and were similar or lower for TAVR than for isolated SAVR in patients 75 years or above in the last 3 years (2017-19). Complication rates of TAVR also declined but permanent pacemaker rates remained high and length of stay substantial (16.7% and median 6 days, respectively, in 2017-19). CONCLUSION: The number of AVR has doubled in a decade and TAVR has become the dominant form of AVR in 2018. The improvement in patient profiles seems to have anticipated the demonstrated benefit of TAVR in intermediate and low-risk patients. In patients 75 years or older, TAVR should be considered as the first option. We also highlight two important areas for improvement, the high permanent pacemaker rates, and the long length of stay even in the contemporary era. Our results may have major implications for clinical practice and policymakers.

Perivalvular Extension of Infective Endocarditis After Transcatheter Aortic Valve Replacement.

BACKGROUND: Infective endocarditis (IE) following transcatheter aortic valve replacement (TAVR) has been associated with a dismal prognosis. However, scarce data exist on IE perivalvular extension (PEE) in such patients. METHODS: This multicenter study included 579 patients who had the diagnosis of definite IE at a median of 171 (53-421) days following TAVR. PEE was defined as the presence of an intracardiac abscess, pseudoaneurysm, or fistula. RESULTS: A total of 105 patients (18.1%) were diagnosed with PEE (perivalvular abscess, pseudoaneurysm, fistula, or a combination in 87, 7, 7, and 4 patients, respectively). A history of chronic kidney disease (adjusted odds ratio [ORadj], 2.08; 95% confidence interval [CI]: 1.27-3.41; P = .003) and IE secondary to coagulase-negative staphylococci (ORadj, 2.71; 95% CI: 1.57-4.69; P < .001) were associated with an increased risk of PEE. Surgery was performed at index IE episode in 34 patients (32.4%) with PEE (vs 15.2% in patients without PEE, P < .001). In-hospital and 2-year mortality rates among PEE-IE patients were 36.5% and 69.4%, respectively. Factors independently associated with an increased mortality were the occurrence of other complications (stroke post-TAVR, acute renal failure, septic shock) and the lack of surgery at index IE hospitalization (padj < 0.05 for all). CONCLUSIONS: PEE occurred in about one-fifth of IE post-TAVR patients, with the presence of coagulase-negative staphylococci and chronic kidney disease determining an increased risk. Patients with PEE-IE exhibited high early and late mortality rates, and surgery during IE hospitalization seemed to be associated with better outcomes.

Fully unsupervised deep mode of action learning for phenotyping high-content cellular images.

MOTIVATION: The identification and discovery of phenotypes from high content screening images is a challenging task. Earlier works use image analysis pipelines to extract biological features, supervised training methods or generate features with neural networks pretrained on non-cellular images. We introduce a novel unsupervised deep learning algorithm to cluster cellular images with similar Mode-of-Action (MOA) together using only the images' pixel intensity values as input. It corrects for batch effect during training. Importantly, our method does not require the extraction of cell candidates and works from the entire images directly. RESULTS: The method achieves competitive results on the labeled subset of the BBBC021 dataset with an accuracy of 97.09% for correctly classifying the MOA by nearest neighbors matching. Importantly, we can train our approach on unannotated datasets. Therefore, our method can discover novel MOAs and annotate unlabeled compounds. The ability to train end-to-end on the full resolution images makes our method easy to apply and allows it to further distinguish treatments by their effect on proliferation. AVAILABILITY AND IMPLEMENTATION: Our code is available at https://github.com/Novartis/UMM-Discovery. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

Contribution and clinical relevance of germline variation to the cancer transcriptome.

BACKGROUND: Somatic alterations in the cancer genome, some of which are associated with changes in gene expression, have been characterized in multiple studies across diverse cancer types. However, less is known about germline variants that influence tumor biology by shaping the cancer transcriptome. METHODS: We performed expression quantitative trait loci (eQTL) analyses using multi-dimensional data from The Cancer Genome Atlas to explore the role of germline variation in mediating the cancer transcriptome. After accounting for associations between somatic alterations and gene expression, we determined the contribution of inherited variants to the cancer transcriptome relative to that of somatic variants. Finally, we performed an interaction analysis using estimates of tumor cellularity to identify cell type-restricted eQTLs. RESULTS: The proportion of genes with at least one eQTL varied between cancer types, ranging between 0.8% in melanoma to 28.5% in thyroid cancer and was correlated more strongly with intratumor heterogeneity than with somatic alteration rates. Although contributions to variance in gene expression was low for most genes, some eQTLs accounted for more than 30% of expression of proximal genes. We identified cell type-restricted eQTLs in genes known to be cancer drivers including LPP and EZH2 that were associated with disease-specific mortality in TCGA but not associated with disease risk in published GWAS. Together, our results highlight the need to consider germline variation in interpreting cancer biology beyond risk prediction.

Priming and polymerization of a bacterial contractile tail structure.

Contractile tails are composed of an inner tube wrapped by an outer sheath assembled in an extended, metastable conformation that stores mechanical energy necessary for its contraction. Contraction is used to propel the rigid inner tube towards target cells for DNA or toxin delivery. Although recent studies have revealed the structure of the contractile sheath of the type VI secretion system, the mechanisms by which its polymerization is controlled and coordinated with the assembly of the inner tube remain unknown. Here we show that the starfish-like TssA dodecameric complex interacts with tube and sheath components. Fluorescence microscopy experiments in enteroaggregative Escherichia coli reveal that TssA binds first to the type VI secretion system membrane core complex and then initiates tail polymerization. TssA remains at the tip of the growing structure and incorporates new tube and sheath blocks. On the basis of these results, we propose that TssA primes and coordinates tail tube and sheath biogenesis.

Isolation and characterization of a large photosystem I-light-harvesting complex II supercomplex with an additional Lhca1-a4 dimer in Arabidopsis.

The biological conversion of light energy into chemical energy is performed by a flexible photosynthetic machinery located in the thylakoid membranes. Photosystems I and II (PSI and PSII) are the two complexes able to harvest light. PSI is the last complex of the electron transport chain and is composed of multiple subunits: the proteins building the catalytic core complex that are well conserved between oxygenic photosynthetic organisms, and, in green organisms, the membrane light-harvesting complexes (Lhc) necessary to increase light absorption. In plants, four Lhca proteins (Lhca1-4) make up the antenna system of PSI, which can be further extended to optimize photosynthesis by reversible binding of LHCII, the main antenna complex of photosystem II. Here, we used biochemistry and electron microscopy in Arabidopsis to reveal a previously unknown supercomplex of PSI with LHCII that contains an additional Lhca1-a4 dimer bound on the PsaB-PsaI-PsaH side of the complex. This finding contradicts recent structural studies suggesting that the presence of an Lhca dimer at this position is an exclusive feature of algal PSI. We discuss the features of the additional Lhca dimer in the large plant PSI-LHCII supercomplex and the differences with the algal PSI. Our work provides further insights into the intricate structural plasticity of photosystems.

Temporal Trends, Characteristics, and Outcomes of Infective Endocarditis After Transcatheter Aortic Valve Replacement.

BACKGROUND: Procedural improvements combined with the contemporary clinical profile of patients undergoing transcatheter aortic valve replacement (TAVR) may have influenced the incidence and outcomes of infective endocarditis (IE) following TAVR. We aimed to determine the temporal trends, characteristics, and outcomes of IE post-TAVR. METHODS: Observational study including 552 patients presenting definite IE post-TAVR. Patients were divided in 2 groups according to the timing of TAVR (historical cohort [HC]: before 2014; contemporary cohort [CC]: after 2014). RESULTS: Overall incidence rates of IE were similar in both cohorts (CC vs HC: 5.45 vs 6.52 per 1000 person-years; P = .12), but the rate of early IE was lower in the CC (2.29‰ vs 4.89‰, P < .001). Enterococci were the most frequent microorganism. Most patients presented complicated IE ( CC: 67.7%; HC: 69.6%; P = .66), but the rate of surgical treatment remained low (CC: 20.7%; HC: 17.3%; P = .32). The CC exhibited lower rates of in-hospital acute kidney injury (35.1% vs 44.6%; P = .036) and in-hospital (26.6% vs 36.4%; P = .016) and 1-year (37.8% vs 53.5%; P < .001) mortality. Higher logistic EuroScore, Staphylococcus aureus etiology, and complications (stroke, heart failure, and acute renal failure) were associated with in-hospital mortality in multivariable analyses (P < .05 for all). CONCLUSIONS: Although overall IE incidence has remained stable, the incidence of early IE has declined in recent years. The microorganism, high rate of complications, and very low rate of surgical treatment remained similar. In-hospital and 1-year mortality rates were high but progressively decreased over time.

Transcatheter aortic valve thrombosis: Data from a French multicenter cohort analysis.

OBJECTIVES: To evaluate the effectiveness of anticoagulant therapies in patients with clinical transcatheter heart valve (THV) thrombosis, to describe complications, and to assess their risk profile was the objectives. BACKGROUND: Little research has been conducted on clinical THV thrombosis. METHODS: Patients with clinical THV thrombosis were identified based on greater than 50% increased transvalvular gradient on transthoracic echocardiogram confirmed by 4-dimensional computed tomography, transesophageal echocardiogram, or regression with anticoagulant therapy. A cohort free from thrombosis for more than 1,100 days postprocedure was used for comparison. RESULTS: Fifty-four patients with clinical THV thrombosis were identified. Most subjects (98.1%) received anticoagulant therapy which was effective (≥50% reduction in transvalvular gradient or return to postprocedure value) in 96%. The rate of serious hemodynamic or embolic complications in the thrombosis population was 31.5%. A multivariate analysis of subjects with and without thrombosis indicated a significantly increased risk of thrombosis from preexisting thrombocytopenia (odds ratio [OR] 9.96), absence of predilatation (OR = 5.67), renal insufficiency (OR = 4.84), and >10 mmHg mean transvalvular gradient postprocedure (OR = 3.36). No recurrence of thrombosis was identified during on average 685 days follow-up. CONCLUSIONS: These data, from one of the largest cohorts with clinical THV thrombosis confirm anticoagulants appear effective. The rate of serious associated complications was high. The findings underline the importance of recognizing risk factors for thrombosis.

Biogenesis and structure of a type VI secretion membrane core complex.

Bacteria share their ecological niches with other microbes. The bacterial type VI secretion system is one of the key players in microbial competition, as well as being an important virulence determinant during bacterial infections. It assembles a nano-crossbow-like structure in the cytoplasm of the attacker cell that propels an arrow made of a haemolysin co-regulated protein (Hcp) tube and a valine-glycine repeat protein G (VgrG) spike and punctures the prey's cell wall. The nano-crossbow is stably anchored to the cell envelope of the attacker by a membrane core complex. Here we show that this complex is assembled by the sequential addition of three type VI subunits (Tss)-TssJ, TssM and TssL-and present a structure of the fully assembled complex at 11.6 Å resolution, determined by negative-stain electron microscopy. With overall C5 symmetry, this 1.7-megadalton complex comprises a large base in the cytoplasm. It extends in the periplasm via ten arches to form a double-ring structure containing the carboxy-terminal domain of TssM (TssMct) and TssJ that is anchored in the outer membrane. The crystal structure of the TssMct-TssJ complex coupled to whole-cell accessibility studies suggest that large conformational changes induce transient pore formation in the outer membrane, allowing passage of the attacking Hcp tube/VgrG spike.

Coherent beam combining of 61 femtosecond fiber amplifiers.

We report on the coherent beam combining of 61 femtosecond fiber chirped-pulse amplifiers in a tiled-aperture configuration along with an interferometric phase measurement technique. Relying on coherent beam recombination in the far field, this technique appears suitable for the combination of a large number of fiber amplifiers. The 61 output beams are stacked in a hexagonal arrangement and collimated through a high fill factor hexagonal micro-lens array. The residual phase error between two fibers is as low as λ/90 RMS, while a combining efficiency of ∼50% is achieved.

Resistance mechanisms to TP53-MDM2 inhibition identified by in vivo piggyBac transposon mutagenesis screen in an Arf-/- mouse model.

Inhibitors of double minute 2 protein (MDM2)-tumor protein 53 (TP53) interaction are predicted to be effective in tumors in which the TP53 gene is wild type, by preventing TP53 protein degradation. One such setting is represented by the frequent CDKN2A deletion in human cancer that, through inactivation of p14ARF, activates MDM2 protein, which in turn degrades TP53 tumor suppressor. Here we used piggyBac (PB) transposon insertional mutagenesis to anticipate resistance mechanisms occurring during treatment with the MDM2-TP53 inhibitor HDM201. Constitutive PB mutagenesis in Arf-/- mice provided a collection of spontaneous tumors with characterized insertional genetic landscapes. Tumors were allografted in large cohorts of mice to assess the pharmacologic effects of HDM201. Sixteen out of 21 allograft models were sensitive to HDM201 but ultimately relapsed under treatment. A comparison of tumors with acquired resistance to HDM201 and untreated tumors identified 87 genes that were differentially and significantly targeted by the PB transposon. Resistant tumors displayed a complex clonality pattern suggesting the emergence of several resistant subclones. Among the most frequent alterations conferring resistance, we observed somatic and insertional loss-of-function mutations in transformation-related protein 53 (Trp53) in 54% of tumors and transposon-mediated gain-of-function alterations in B-cell lymphoma-extra large (Bcl-xL), Mdm4, and two TP53 family members, resulting in expression of the TP53 dominant negative truncations ΔNTrp63 and ΔNTrp73. Enhanced BCL-xL and MDM4 protein expression was confirmed in resistant tumors, as well as in HDM201-resistant patient-derived tumor xenografts. Interestingly, concomitant inhibition of MDM2 and BCL-xL demonstrated significant synergy in p53 wild-type cell lines in vitro. Collectively, our findings identify several potential mechanisms by which TP53 wild-type tumors may escape MDM2-targeted therapy.