Polarity establishment in the plant zygote at a glance.

The complex structures of multicellular organisms originate from a unicellular zygote. In most angiosperms, including Arabidopsis thaliana, the zygote is distinctly polar and divides asymmetrically to produce an apical cell, which generates the aboveground part of the plant body, and a basal cell, which generates the root tip and extraembryonic suspensor. Thus, zygote polarity is pivotal for establishing the apical-basal axis running from the shoot apex to the root tip of the plant body. The molecular mechanisms and spatiotemporal dynamics behind zygote polarization remain elusive. However, advances in live-cell imaging of plant zygotes have recently made significant insights possible. In this Cell Science at a Glance article and the accompanying poster, we summarize our understanding of the early steps in apical-basal axis formation in Arabidopsis, with a focus on de novo transcriptional activation after fertilization and the intracellular dynamics leading to the first asymmetric division of the zygote.

Comprehensive and quantitative analysis of intracellular structure polarization at the apical-basal axis in elongating Arabidopsis zygotes.

A comprehensive and quantitative evaluation of multiple intracellular structures or proteins is a promising approach to provide a deeper understanding of and new insights into cellular polarity. In this study, we developed an image analysis pipeline to obtain intensity profiles of fluorescent probes along the apical-basal axis in elongating Arabidopsis thaliana zygotes based on two-photon live-cell imaging data. This technique showed the intracellular distribution of actin filaments, mitochondria, microtubules, and vacuolar membranes along the apical-basal axis in elongating zygotes from the onset of cell elongation to just before asymmetric cell division. Hierarchical cluster analysis of the quantitative data on intracellular distribution revealed that the zygote may be compartmentalized into two parts, with a boundary located 43.6% from the cell tip, immediately after fertilization. To explore the biological significance of this compartmentalization, we examined the positions of the asymmetric cell divisions from the dataset used in this distribution analysis. We found that the cell division plane was reproducibly inserted 20.5% from the cell tip. This position corresponded well with the midpoint of the compartmentalized apical region, suggesting a potential relationship between the zygote compartmentalization, which begins with cell elongation, and the position of the asymmetric cell division.

Efficacy and safety of atrial fibrillation ablation in heart failure patients with left ventricular ejection fraction less than 50.

INTRODUCTION: The efficacy of catheter ablation in patients with low cardiac function has been previously reported; however, only a few studies have included mid-range ejection fraction (mrEF). This study aimed to evaluate the efficacy and safety of atrial fibrillation (AF) ablation in patients with left ventricular ejection fraction (LVEF) < 50%. METHODS: This study retrospectively analyzed 79 patients (reduced ejection fraction [rEF]/mrEF, 38/41; paroxysmal/persistent, 37/42; heart failure hospitalizations within one year before ablation, 36 [45.6%]) who underwent the first ablation procedure at our hospital from April 2017 to December 2021. Radiofrequency ablation and cryoablation were performed for 69 and 10 patients, respectively. RESULTS: Complications included pacemaker implantation for postoperative sick sinus syndrome in one patient and inguinal hematoma in one patient. Regarding efficacy, there were significant postoperative improvements in echocardiographic data, blood test values, and diuretic use. After a mean follow-up of 60 months, 86.1% patients had no AF recurrence. There were 9 heart failure hospitalizations (11.4%) and 5 all-cause deaths (6.3%); no significant differences were found between the rEF and mrEF groups. No significant predictors of AF recurrence were found in preoperative patient characteristics. CONCLUSION: AF ablation in patients with LVEF <50% significantly improved cardiac and renal functions with few complications, resulting in a high non-recurrence rate and reduced heart failure.

Coordinate Normalization of Live-Cell Imaging Data Reveals Growth Dynamics of the Arabidopsis Zygote.

Polarization of the zygote defines the body axis during plant development. In Arabidopsis (Arabidopsis thaliana), the zygote becomes polarized and elongates in the longitudinal direction, ultimately forming the apical-basal axis of the mature plant. Despite its importance, the mechanism for this elongation remains poorly understood. Based on live-cell imaging of the zygote, we developed new image analysis methods, referred to as coordinate normalization, that appropriately fix and align positions in an image, preventing fluctuation across a temporal sequence of images. Using these methods, we discovered that the zygote elongates only at its apical tip region, similar to tip-growing cells such as pollen tubes and root hairs. We also investigated the spatiotemporal dynamics of the apical tip contour of the zygote and observed that the zygote tip retains its isotropic, hemispherical apical shape during cell elongation. By looking at the elliptical fitting of the contour over time, we further discovered that the apical cell tip becomes thinner at first and then thickens, with a transient increase in growth speed that is followed by the first cell division. We performed the same series of analyses using root hairs and established that both the hemispherical tip shape and the changes in growth rate associated with changes in tip size are specific to the zygote. In summary, the Arabidopsis zygote undergoes directional elongation as a tip-growing cell, but its tip retains an unusual isotropic shape, and the manner of growth changes with the developmental stage.

Contrast-enhanced computed tomography for optimizing the outcomes of pulmonary vein isolation with cryoablation -the role of isolation of PVs including carina.

PURPOSE: Compared with conventional pulmonary vein isolation (PVI) with radiofrequency ablation, PVI with cryoballoon is an easier and shorter procedure without reconnection, particularly in the superior pulmonary vein. However, the durability of the cryoballoon may be reduced due to anatomical factors and the position of the pulmonary vein (PV). Further, inadequate isolation of the carina leads to recurrence of atrial fibrillation (AF). We aimed to determine whether using contrast-enhanced computed tomography (CT) for patient selection improves the early success rate and prevents the recurrence of AF in PVI with cryoballoon. METHODS: We evaluated patients who underwent ablation for paroxysmal atrial fibrillation in our hospital between July 2019 and November 2020. After excluding patients with contraindications for cryoablation, 50 patients were selected through visual inspection of the results of preoperative contrast-enhanced CT. A treatment plan was established, and the clinical course and outcomes were followed up. RESULTS: Of the 200 PVs of the 50 patients, only 8 PVs (4%) were incompletely isolated with a single cryoablation. Six of the eight PVs were successfully isolated with additional cryoablation. Only 2 patients (4%) underwent additional PVI with radiofrequency ablation. Four patients had AF recurrence within a mean follow-up period of 14.3 ± 5.1 months. The rate of sinus rhythm maintenance was 92%. PV reconnection was observed in 2 patients. None of the patients had postoperative atrial flutter. CONCLUSIONS: Selecting patients for cryoablation according to contrast-enhanced CT findings made the procedure easier to perform, leading to improved early success rates and clinical course.

Characterization and visualization of murine coagulation factor VIII-producing cells in vivo.

Coagulation factors are produced from hepatocytes, whereas production of coagulation factor VIII (FVIII) from primary tissues and cell species is still controversial. Here, we tried to characterize primary FVIII-producing organ and cell species using genetically engineered mice, in which enhanced green fluorescent protein (EGFP) was expressed instead of the F8 gene. EGFP-positive FVIII-producing cells existed only in thin sinusoidal layer of the liver and characterized as CD31high, CD146high, and lymphatic vascular endothelial hyaluronan receptor 1 (Lyve1)+. EGFP-positive cells can be clearly distinguished from lymphatic endothelial cells in the expression profile of the podoplanin- and C-type lectin-like receptor-2 (CLEC-2)+. In embryogenesis, EGFP-positive cells began to emerge at E14.5 and subsequently increased according to liver maturation. Furthermore, plasma FVIII could be abolished by crossing F8 conditional deficient mice with Lyve1-Cre mice. In conclusion, in mice, FVIII is only produced from endothelial cells exhibiting CD31high, CD146high, Lyve1+, CLEC-2+, and podoplanin- in liver sinusoidal endothelial cells.

Dynamic Rearrangement and Directional Migration of Tubular Vacuoles are Required for the Asymmetric Division of the Arabidopsis Zygote.

In most flowering plants, the asymmetric cell division of zygotes is the initial step that establishes the apical-basal axis. In the Arabidopsis zygote, vacuolar accumulation at the basal cell end is crucial to ensure zygotic division asymmetry. Despite the importance, it was unclear whether this polar vacuolar distribution was achieved by predominant biogenesis at the basal region or by directional movement after biogenesis. Here, we found that apical and basal vacuolar contents are dynamically exchanged via a tubular vacuolar network and the vacuoles gradually migrate toward the basal end. The mutant of a vacuolar membrane protein, SHOOT GRAVITROPISM2 (SGR2), failed to form tubular vacuoles, and the mutant of a putative vacuolar fusion factor, VESICLE TRANSPORT THROUGH INTERACTION WITH T-SOLUBLE N-ETHYLMALEIMIDE-SENSITIVE FUSION PROTEIN ATTACHMENT PROTEIN RECEPTORS (SNARES) 11 (VTI11), could not flexibly rearrange the vacuolar network. Both mutants failed to exchange the apical and basal vacuolar contents and to polarly migrate the vacuoles, resulting in a more symmetric division of zygotes. Additionally, we observed that in contrast to sgr2, the zygotic defects of vti11 were rescued by the pharmacological depletion of phosphatidylinositol 3-phosphate (PI3P), a distinct phospholipid in the vacuolar membrane. Thus, SGR2 and VTI11 have individual sites of action in zygotic vacuolar membrane processes. Further, a mutant of YODA (YDA) mitogen-activated protein kinase kinase kinase, a core component of the embryonic axis formation pathway, generated the proper vacuolar network; however, it failed to migrate the vacuoles toward the basal region, which suggests impaired directional cues. Overall, we conclude that SGR2- and VTI11-dependent vacuolar exchange and YDA-mediated directional migration are necessary to achieve polar vacuolar distribution in the zygote.

Isolated bilateral external iliac artery dissections with emotional stress.

We present a patient with isolated bilateral external iliac artery dissections associated with emotional stress. The diagnosis should be kept in mind in young, fit patients presenting lower back pain occurring subsequent to emotional stress.

A case of accessory pathway mapped with ultra-high-resolution mapping led to a coronary sinus diverticulum.

Ultra-high-resolution mapping is useful in the ablation of accessory pathways. However, in patients with accessory pathways in the coronary sinus (CS) diverticulum, treatment with endocardial ablation may be challenging. Patients suspected of having subepicardial accessory pathways may require the examination of the venous anomaly using CS angiography.

Secondary Cardiac Lymphoma Presenting as Sick Sinus Syndrome and Atrial Fibrillation Which Required Leadless Pacemaker Implantation.

Cardiac involvement of malignant lymphoma is relatively common, although such a phenomenon has subclinical manifestations that are difficult to detect. We herein describe a patient with atrial fibrillation and sick sinus syndrome as the main symptoms. Computed tomography showed a mass in the right atrium extending into the superior vena cava (SVC). We implanted the patient with a leadless pacemaker. Transvenous biopsy revealed a diffuse large B-cell lymphoma. The patient was treated successfully with chemotherapy including rituximab. This case suggested that cardiac lymphoma may cause sick sinus syndrome, and leadless pacemaker implantation is a safe treatment option in patients with partial SVC obstruction.

Efficacy of isoproterenol in the evaluation of dormant conduction and arrhythmogenic foci identification in atrial fibrillation ablation.

BACKGROUND: Catheter ablation for atrial fibrillation (AF) is an established therapy. However, postoperative recurrence is a serious issue caused by the reconduction of the isolated pulmonary veins (PV) and the onset of non-PV foci. The objectives of this study were to elucidate dormant conduction, confirm PV arrhythmia substrate, induce non-PV foci after PV isolation, and assess the acute efficacy of high dose isoproterenol (ISP) when administered in addition to adenosine. METHODS: The study consisted of 100 patients with drug-refractory AF (paroxysmal and persistent) who underwent ablation therapy (either radio-frequency or cryoballoon ablation) as the first-line of therapy at our hospital. All patients first underwent PV isolation (PVI) and were administered adenosine followed by ISP (6 µg × 5 min). The effects were observed, and the therapeutic strategy was evaluated. RESULTS: Persistent dormant conduction due to ISP administration was observed in 13 patients. In over half of the patients, arrhythmia substrates were identified in the PV. Ten patients presented with persistent PV firing. The ablation of non-PV foci was additionally performed in 23 patients. CONCLUSIONS: We found that dormant conduction, as a result of ISP administration, is persistent and ISP is useful when performing an ablation. In addition, ISP administration is useful for the identification of PV arrhythmia substrates and induction of non-PV foci. However, the effectiveness of ISP may be partially due to the complementary effect of adenosine, and, therefore, a combination of the two drugs seems preferable.

CURLED LATER1 encoding the largest subunit of the Elongator complex has a unique role in leaf development and meristem function in rice.

The Elongator complex, which is conserved in eukaryotes, has multiple roles in diverse organisms. In Arabidopsis thaliana, Elongator is shown to be involved in development, hormone action and environmental responses. However, except for Arabidopsis, our knowledge of its function is poor in plants. In this study, we initially carried out a genetic analysis to characterize a rice mutant with narrow and curled leaves, termed curled later1 (cur1). The cur1 mutant displayed a heteroblastic change, whereby the mutant leaf phenotype appeared specifically at a later adult phase of vegetative development. The shoot apical meristem (SAM) was small and the leaf initiation rate was low, suggesting that the activity of the SAM seemed to be partially reduced in cur1. We then revealed that CUR1 encodes a yeast ELP1-like protein, the largest subunit of Elongator. Furthermore, disruption of OsELP3 encoding the catalytic subunit of Elongator resulted in phenotypes similar to those of cur1, including the timing of the appearance of mutant phenotypes. Thus, Elongator activity seems to be specifically required for leaf development at the late vegetative phase. Transcriptome analysis showed that genes involved in protein quality control were highly upregulated in the cur1 shoot apex at the later vegetative phase, suggesting the restoration of impaired proteins probably produced by partial defects in translational control due to the loss of function of Elongator. The differences in the mutant phenotype and gene expression profile between CUR1 and its Arabidopsis ortholog suggest that Elongator has evolved to play a unique role in rice development.

Mitochondrial dynamics and segregation during the asymmetric division of Arabidopsis zygotes.

The zygote is the first cell of a multicellular organism. In most angiosperms, the zygote divides asymmetrically to produce an embryo-precursor apical cell and a supporting basal cell. Zygotic division should properly segregate symbiotic organelles, because they cannot be synthesized de novo. In this study, we revealed the real-time dynamics of the principle source of ATP biogenesis, mitochondria, in Arabidopsis thaliana zygotes using live-cell observations and image quantifications. In the zygote, the mitochondria formed the extended structure associated with the longitudinal array of actin filaments (F-actins) and were polarly distributed along the apical-basal axis. The mitochondria were then temporally fragmented during zygotic division, and the resulting apical cells inherited mitochondria at higher concentration compared to the basal cells. Further observation of postembryonic organs showed that these mitochondrial behaviours are characteristic of the zygote. Overall, our results showed that the zygote has spatiotemporal regulation that unequally distributes the mitochondria.

Characterization of a half-pipe-like leaf1 mutant that exhibits a curled leaf phenotype.

Leaf forms are diverse in angiosperms, and different types of cells are differentiated depending on the species. Rice leaves are composed of a leaf blade, a leaf sheath and the junction region between them. Cells with characteristic features, such as bulliform cells and sclerenchyma cells, are differentiated in the leaf blade, together with standard epidermal and mesophyll cells. To understand the genetic mechanism underlying leaf morphogenesis in rice, we focused on a mutant, half-pipe-like leaf1 (hal1), whose leaves are adaxially curled. Histological observation revealed that the bulliform cells, which are responsible for leaf rolling under dry conditions, were small in size and abnormal in shape in a semidominant hal1-d mutant. Bulliform cell files were often ambiguous in semi-transparent hal1-d leaves cleared by the TOMEI method, suggesting that the bulliform cells were undeveloped. Therefore, a reduction in the growth of the bulliform cells seemed to be a major cause of leaf curling in the hal1-d mutant. The hal1-d mutation also affected the size of the leaf blade and the spikelet.