A novel RAB11-containing adaptor complex anchoring myosin-5 to secretory vesicles

Hyphal fungi grow rapidly by apical extension, providing a notorious example of polarized growth. The continuous supply of secretory vesicles necessary to meet the demands of the extending tip and the long intracellular distances existing between the tip and the basal septum, often localized > 100 µm away from the former, impose the need of efficient networks of intracellular traffic involving exquisite cooperation between microtubule- and actin-mediated transport. In Aspergillus nidulans kinesin-1 conveys secretory vesicles to the hyphal tip, where they are transferred to myosin-5, which focuses them at the growing apex, thereby determining cell shape. This relay mechanism and the central role played by myosin-5 in hyphal morphogenesis suggested that the mechanisms anchoring secretory vesicles to this motor should involve specific adaptor(s) ensuring the robustness of actomyosin-dependent transport.Secretory vesicles are charged with RAB11, a regulatory GTPase that determines the Golgi to post-Golgi identity transition. By using a combination of shotgun proteomics, GST-RAB pull-down assays, in vitro reconstitution experiments, targeted reverse genetics and multidimensional fluorescence microscopy with endogenously tagged proteins we show that RAB11, the master regulator of fungal exocytosis, mediates myosin-5 engagement both by contacting the motor and by recruiting UDS1, a homologue of an as yet uncharacterized Schizosaccharomyces protein ‘upregulated during mitosis’, which we demonstrate to be a novel RAB11 effector. Analytical ultracentrifugation determined that UDS1 is an elongated dimer and negative-stain electron microscopy showed that, in agreement, UDS1 is rod-shaped. UDS1 does not contact myosin-5 directly, but rather recruits the coiled-coil HMSV, which bridges RAB11/UDS1 to myosin-5. An HMSV-scaffolded complex containing UDS1 and myosin-5 is present in cells, and a RAB11-UDS1-HMSV complex can be reconstituted in vitro in a RAB nucleotide state-dependent manner. In the absence of UDS1/HMSV the steady state levels of myosin-5 at the apical vesicle supply center diminish markedly, such that microtubule-dependent transport spreading vesicles across the apical dome predominates over apex-focused actin-mediated transport. As a consequence, RAB11 and chitin-synthase B (a cargo of the RAB11 pathway) are not focused at the apex, being distributed instead across the apical dome. Therefore, the RAB11 effector UDS1/HMSV cooperates with the GTPase to adapt secretory vesicles to myosin-5, which is required for the apical targeting of RAB11 cargoes and thus for the normal morphology of the hyphae.

Laminopathies: Should Wenckebach be a cause for concern? A case report

Background LMNA cardiomyopathy is a cause of dilated cardiomyopathy (DCM) characterised by aggressive heart failure, high risk of arrhythmias and sudden cardiac death. We present a case of a male presenting with a LMNA mutation with an aggressive DCM leading to sudden cardiac death (SCD). Case summary A 42-year-old male presented with the feeling of lethargy and intermittent dizziness. ECG demonstrated AV block in keeping with Mobitz type 1, at a rate of 40 b.p.m. and cardiac monitoring showed non-sustained VT. CMR imaging showed preserved left ventricular function (EF 59%) but features suggesting DCM. These included mild LV dilatation with an EDV of 213 mL and late enhancement showing a single mid myocardial focus of high signal over the distal RV insertion point inferiorly and a linear area of high signal over the basal septum. After discussion at cardiology multi-disciplinary meeting a pacemaker was implanted so that beta-blockers could be initiated to suppress the ventricular arrhythmias. A laminopathy was suspected and if this was confirmed from genetic testing the plan was to upgrade to an implantable defibrillator. Due to stability this was decided to be done in an outpatient setting. He unfortunately had an out of hospital VF arrest and died. Post-mortem showed subtle cardiomyopathy in keeping with a DCM. Genetic tests results were returned a few months later which confirmed a pathogenic variant in LMNA. Discussion Because of the complexity of LMNA-related cardiac disease, they should be managed and followed up in centres with special expertise in inherited cardiomyopathy.

Obesity in the absence of comorbidities is not related to clinically meaningful left ventricular hypertrophy

Obesity is associated with the development of left ventricular (LV) hypertrophy. Whether obesity in in the absence of comorbidities can cause LV hypertrophy to an extent which could create diagnostic uncertainty with pathological states (such as hypertrophic cardiomyopathy) is unknown. We used cine cardiovascular magnetic resonance imaging to precisely measure LV wall thickness in the septum and lateral wall in 764 people with body mass indices ranging from 18.5 kg/m2 to 59.2 kg/m2 in the absence of major comorbidities. Obesity was related to LV wall thickness across the cohort (basal septum r 0.30, P < 0.001 and basal lateral wall r 0.18, P < 0.001). Although no participant had hypertension, these associations remained highly significant after controlling for systolic blood pressure (all P < 0.01). Each 10 kg/m2 increase in BMI was associated with an increase in basal septal wall thickness of 1.0 mm males and 0.8 mm in females, with no statistically significant difference between genders (P = 0.1). Even in class 3 obesity (BMI > 40 kg/m2), no LV wall thickness > 13.4 mm in males or > 12.7 mm in females was observed in this cohort. We confirm that obesity in the absence of comorbidities is associated with LV hypertrophy, and establish that the magnitude of this change is modest even in severe obesity. LV hypertrophy > 14 mm cannot safely be attributed to obesity alone and alternative diagnoses should be considered.

Postinfarction posterobasal ventricular septal defect closure with a triple-layer patch

We present the case of a 65-year-old patient who developed a large posterobasal ventricular septal defect resulting from an extensive acute myocardial infarction involving the inferior and basal septum and wall. We repaired the interventricular lesion by verticalizing the cardiac apex to perform a left posterobasal ventriculotomy. We removed a great part of the residual infarcted tissue, leaving the residual scar in place. Our technique first involved creating a double-layer patch comprising heterologous pericardium and a non-collagen-impregnated Sauvage Dacron patch, fixed with single pledgeted U-stitches from the right side of the anterior septum; then we applied a third layer of heterologous pericardium on the left side of the septum in order to have only a pericardial surface in contact with blood on both ventricular sides. A running suture was used to complete the procedure from the middle to the posterior rim of the ventricular septal defect.

Abstract 15426: Comparison of Multimodality Imaging in Mitral Leaflet Lengths in Patients Undergoing Surgical Myectomy: A Prospective Study in Hypertrophic Obstructive Cardiomyopathy Patients

Introduction: In hypertrophic obstructive cardiomyopathy (HOCM), mitral valve (MV) leaflets in often contribute to left ventricular outflow tract obstruction (LVOTO). Hence, MV assessment is crucial during surgical planning. 2 or 3-dimensional transesophageal echocardiography (2D or 3D TEE) & cardiac magnetic resonance (CMR) are used to measure MV length. Hypothesis: We sought to compare MV leaflet lengths using intraoperative TEE [2D, zoom 3D, automatic quantification of mitral valve (AMVQ)], & preoperative CMR. Methods: We prospectively studied 50 HOCM patients (59±12 years, 46% men, basal septum 18±5 mm, LVOT gradient 87 ±56 mmHg) undergoing surgical relief of LVOTO. We compared MV leaflet length on a) long-axis 2DTEE b) 3DTEE using multiplanar reconstruction c) AMVQ, EchoPAC, General Electric & d) CMR. Results: Mean anterior leaflet lengths (mm) were as follows: 2D TEE (3.3 ±0.3), 3DTEE (2.9±0.5), CMR (3.1±0.4), & AMVQ (2.9±0.5). Mean posterior leaflet lengths were 1.7±0.3, 1.7±0.4, & 1.7±0.2 & 1.9±0.4 mm, respectively. Assuming 3DTEE as the gold standard, the closest correlation for anterior leaflet was with CMR (average overestimation by CMR of 0.5 mm [root mean square deviation or RMSE% 17]), intermediate correlation with 2DTEE (average deviation of 0.6 mm [RMSE%:21]) & no correlation with AMVQ (deviation of 0.7mm [RMSE% 24]), Fig 1A-C & 2A-C. No correlation was found for posterior leaflet,Fig 1D-F & 2D-F. Conclusions: There are significant differences in measuring MV lengths using different imaging techniques. In HOCM patients undergoing surgery, precise measurement of MV leaflet lengths is crucial & extrapolation from one technique to other is not recommended.

What is the mid-wall linear high intensity “lesion” on cardiovascular magnetic resonance late gadolinium enhancement?

Background Cardiovascular magnetic resonance (CMR) late gadolinium enhancement (LGE) is a valuable technique for detecting myocardial disorders and fibrosis. However, we sometimes observe a linear, mid-wall high intensity signal in the basal septum in the short axis view, which often presents diagnostic difficulties in the clinical setting. The purpose of this study was to compare the linear, mid-wall high intensity in the basal septum identified by LGE with the anterior septal perforator arteries identified by coronary computed tomography angiography (CorCTA). Methods We retrospectively selected 148 patients who underwent both CorCTA and CMR LGE within 1 year. In the interpretation of LGE, we defined a positive linear high intensity (LHI+) as follows: ① LHI in the basal septum and ② observable for 1.5 cm or more. All other patients were defined as a negative LHI (LHI-). In LHI+ patients, we assessed the correlation between the LHI length and the septal perforator artery length on CorCTA. We also compared the length of the septal perforator artery on CorCTA between LHI+ patients and LHI- patients. Results A population of 111 patients were used for further analysis. Among these , there were 55 LHI+ patients and 56 LHI- patients. In LHI+ patients, linear regression analysis revealed that there was a good agreement between LGE LHI and septal perforator arteries by CorCTA in terms of length measurements. The measured length of the anterior septal perforator arteries was significantly shorter in LHI- patients than in LHI+ patients (10 ± 8 mm vs. 21 ± 8 mm; P < 0.05). Conclusions The LHI observed in the basal septum on short axis LGE may reflect contrast enhancement of the anterior septal perforator arteries. It is important to interpret this septal LHI against knowledge of anatomic structure, to avoid misinterpretations of LGE and prevent misdiagnosis.

Reference ranges for the fetal mitral, tricuspid, and interventricular septum annular plane systolic excursions (mitral annular plane systolic excursion, tricuspid annular plane systolic excursion, and septum annular plane systolic excursion) between 20 and 36 + 6 weeks of gestation

ObjectivesThis study aimed to establish reference ranges for fetal mitral, tricuspid, and interventricular septum annular plane systolic excursions (MAPSE, TAPSE, and SAPSE) in normal pregnant women between 20 and 36 + 6 weeks of gestation.MethodsThis prospective and cross-sectional study included 360 low-risk singleton pregnancies between 20 and 36 + 6 weeks of gestation. MAPSE, TAPSE, and SAPSE were measured by M-mode in real time in an apical or basal four-chamber view through placing the cursor at the atrioventricular junction, marked by the valve rings at the tricuspid, mitral, and basal septum, respectively. A regression analysis was done to determine the appropriate polynomial equation model for both measurements and standard deviation (SD) values in relation to gestational age (GA). The intra- and inter-observer reproducibility was evaluated using the concordance correlation coefficient (CCC) and limits of agreement (LoA).ResultsThere was a significant positive correlation between MAPSE (r=0.705, p<0.0001), TAPSE (r=0.804, p<0.0001), and SAPSE (r=0.690, p<0.0001) and GA. The mean of each parameter ranged as follows: 2.87–5.56 mm, MAPSE; 3.98–8.07 mm, TAPSE; and 2.34–4.21 mm, SAPSE. Poor/moderate intra- and inter-observer reliability (CCC between 0.70 and 0.90) and poor/moderate agreement of all the tested parameters were evaluated (LoA between 10 and 50%).ConclusionsReference values were established for the fetal MAPSE, TAPSE, and SAPSE between 20 and 36 + 6 weeks of gestation in low-risk pregnant women. These parameters showed poor/moderate reproducibility.