4D light sheet imaging, computational reconstruction, and cell tracking in mouse embryos.

As light sheet fluorescence microscopy (LSFM) becomes widely available, reconstruction of time-lapse imaging will further our understanding of complex biological processes at cellular resolution. Here, we present a comprehensive workflow for in toto capture, processing, and analysis of multi-view LSFM experiments using the ex vivo mouse embryo as a model system of development. Our protocol describes imaging on a commercial LSFM instrument followed by computational analysis in discrete segments, using open-source software.

Synthetic organizer cells guide development via spatial and biochemical instructions.

In vitro development relies primarily on treating progenitor cells with media-borne morphogens and thus lacks native-like spatial information. Here, we engineer morphogen-secreting organizer cells programmed to self-assemble, via cell adhesion, around mouse embryonic stem (ES) cells in defined architectures. By inducing the morphogen WNT3A and its antagonist DKK1 from organizer cells, we generated diverse morphogen gradients, varying in range and steepness.

Heart tube morphogenesis is regulated by segment-specific gene regulatory networks controlled by MEF2C.

The transcription factor MEF2C plays a critical role in the development of the linear heart tube, but the specific transcriptional networks controlled by MEF2C remain largely undefined. To address this, we performed combined single-nucleus RNA-and ATAC-sequencing on wild type and MEF2C-null embryos at distinct stages of development. We identified a broadly "posteriorized" cardiac gene signature and chromatin landscape throughout the heart tube in the absence of MEF2C.

Redefining feasibility in clinical trials: Collaborative approaches for improved site selection.

Background: This Site Feasibility Task Force convened to assess the complex and burdensome process of site feasibility in clinical trials. The objective was to create mutual understanding of challenges and provide suggestions for improving collaboration among sponsors, contract research organizations (CROs), and sites.

Methods: The task force was composed of representatives from sponsors, CROs and sites (43 % Sites, 20 % Site Networks, 10 % Small/mid-size sponsors, 10 % Small/mid-size CROs, 10 % Large sponsors, 7 % Large CROs).

Intravenous lidocaine for postoperative analgesia management in paediatrics: A systematic review with meta-analysis of published studies.

Background: The administration of intravenous lidocaine during the peri-operative period may improve pain management after paediatric surgery.

Objective: To explore the decrease in postoperative pain intensity and opioid consumption associated with peri-operative lidocaine administration in the paediatric population.

Design: A systematic review with meta-analysis of randomised controlled trials and a Grading of Recommendations Assessment, Development and Evaluation (GRADE) analysis.

CDX2 dose-dependently influences the gene regulatory network underlying human extraembryonic mesoderm development.

Loss of Cdx2 in vivo leads to stunted development of the allantois, an extraembryonic mesoderm-derived structure critical for nutrient delivery and waste removal in the early embryo. Here, we investigate how CDX2 dose-dependently influences the gene regulatory network underlying extraembryonic mesoderm development. By engineering human induced pluripotent stem cells (hiPSCs) consisting of wild-type (WT), heterozygous (CDX2-Het), and homozygous null CDX2 (CDX2-KO) genotypes, differentiating these cells in a 2D gastruloid model, and subjecting these cells to single-nucleus RNA and ATAC sequencing, we identify several pathways that are dose-dependently regulated by CDX2 including VEGF and non-canonical WNT.

TBXT dose sensitivity and the decoupling of nascent mesoderm specification from EMT progression in 2D human gastruloids.

In the nascent mesoderm, TBXT expression must be precisely regulated to ensure that cells exit the primitive streak and pattern the anterior-posterior axis, but how varying dosage informs morphogenesis is not well understood. In this study, we define the transcriptional consequences of TBXT dosage reduction during early human gastrulation using human induced pluripotent stem cell models of gastrulation and mesoderm differentiation. Multi-omic single-nucleus RNA and single-nucleus ATAC sequencing of 2D gastruloids comprising wild-type, TBXT heterozygous or TBXT null human induced pluripotent stem cells reveal that varying TBXT dosage does not compromise the ability of a cell to differentiate into nascent mesoderm, but instead directly influences the temporal progression of the epithelial-to-mesenchymal transition with wild type transitioning first, followed by TBXT heterozygous and then TBXT null.

A disrupted compartment boundary underlies abnormal cardiac patterning and congenital heart defects.

Failure of septation of the interventricular septum (IVS) is the most common congenital heart defect (CHD), but mechanisms for patterning the IVS are largely unknown. We show that a progenitor lineage forms a compartment boundary bisecting the IVS. This coordinated population originates at a first- and second heart field interface, subsequently forming a morphogenetic nexus.

CDX2 dose-dependently influences the gene regulatory network underlying human extraembryonic mesoderm development.

Proper regulation of gene dosage is critical for the development of the early embryo and the extraembryonic tissues that support it. Specifically, loss of leads to stunted development of the allantois, an extraembryonic mesoderm-derived structure critical for nutrient delivery and waste removal in the early embryo. In this study, we investigate how CDX2 dose-dependently influences the gene regulatory network underlying extraembryonic mesoderm development.

TBXT dose sensitivity and the decoupling of nascent mesoderm specification from EMT progression in 2D human gastruloids.

In the nascent mesoderm, levels of Brachyury (TBXT) expression must be precisely regulated to ensure cells exit the primitive streak and pattern the anterior-posterior axis, but how this varying dosage informs morphogenesis is not well understood. In this study, we define the transcriptional consequences of TBXT dose reduction during early human gastrulation using human induced pluripotent stem cell (hiPSC)-based models of gastrulation and mesoderm differentiation. Multiomic single-nucleus RNA and single-nucleus ATAC sequencing of 2D gastruloids comprised of WT, TBXT heterozygous (TBXT-Het), or TBXT null (TBXT-KO) hiPSCs reveal that varying TBXT dosage does not compromise a cell's ability to differentiate into nascent mesoderm, but that the loss of TBXT significantly delays the temporal progression of the epithelial to mesenchymal transition (EMT).

Spatial and temporal organization of the genome: Current state and future aims of the 4D nucleome project.

The four-dimensional nucleome (4DN) consortium studies the architecture of the genome and the nucleus in space and time. We summarize progress by the consortium and highlight the development of technologies for (1) mapping genome folding and identifying roles of nuclear components and bodies, proteins, and RNA, (2) characterizing nuclear organization with time or single-cell resolution, and (3) imaging of nuclear organization. With these tools, the consortium has provided over 2,000 public datasets.

Day Surgery in Children Undergoing Retroperitoneal Robot-assisted Laparoscopic Pyeloplasty: Is It Safe and Feasible?

Background: Robot-assisted pyeloplasty is the most frequently performed robotic procedure in children. A retroperitoneal approach limits surgical trauma and avoids peritoneal irritation. This led to the establishment of the criteria for day surgery (DS) and a related clinical care pathway.

A Mesp1-dependent developmental breakpoint in transcriptional and epigenomic specification of early cardiac precursors.

Transcriptional networks governing cardiac precursor cell (CPC) specification are incompletely understood owing, in part, to limitations in distinguishing CPCs from non-cardiac mesoderm in early gastrulation. We leveraged detection of early cardiac lineage transgenes within a granular single-cell transcriptomic time course of mouse embryos to identify emerging CPCs and describe their transcriptional profiles. Mesp1, a transiently expressed mesodermal transcription factor, is canonically described as an early regulator of cardiac specification.

French survey of sedation practices for pediatric magnetic resonance and computed tomography imaging.

Background: Pediatric magnetic resonance imaging (MRI) and computed tompgraphy (CT) require patient immobility and therefore often require sedation or general anesthesia of patients. Consensus on these procedures is lacking in France.

Objective: Thus, the aim of this study was to describe the current sedation practices for pediatric MRI and CT in France.

Graded mesoderm assembly governs cell fate and morphogenesis of the early mammalian heart.

Using four-dimensional whole-embryo light sheet imaging with improved and accessible computational tools, we longitudinally reconstruct early murine cardiac development at single-cell resolution. Nascent mesoderm progenitors form opposing density and motility gradients, converting the temporal birth sequence of gastrulation into a spatial anterolateral-to-posteromedial arrangement. Migrating precardiac mesoderm does not strictly preserve cellular neighbor relationships, and spatial patterns only become solidified as the cardiac crescent emerges.

Coronal STIR MRI sequences in unexplained limping in children under 6 years old: A single-center retrospective study of 130 cases.

Introduction: Limping is a common presenting symptom in young children. Clinical examination backed up by laboratory analysis, standard radiography, and/or ultrasound may fail to determine the diagnosis, and limping may prove persistent, requiring repeated consultation. Magnetic resonance imaging (MRI) can suggest the etiology or provide welcome reassurance when normal.

Cell Layers: uncovering clustering structure in unsupervised single-cell transcriptomic analysis.

Motivation: Unsupervised clustering of single-cell transcriptomics is a powerful method for identifying cell populations. Static visualization techniques for single-cell clustering only display results for a single resolution parameter. Analysts will often evaluate more than one resolution parameter but then only report one.

Transcription Factor GATA4 Regulates Cell Type-Specific Splicing Through Direct Interaction With RNA in Human Induced Pluripotent Stem Cell-Derived Cardiac Progenitors.

Background: GATA4 (GATA-binding protein 4), a zinc finger-containing, DNA-binding transcription factor, is essential for normal cardiac development and homeostasis in mice and humans, and mutations in this gene have been reported in human heart defects. Defects in alternative splicing are associated with many heart diseases, yet relatively little is known about how cell type- or cell state-specific alternative splicing is achieved in the heart. Here, we show that GATA4 regulates cell type-specific splicing through direct interaction with RNA and the spliceosome in human induced pluripotent stem cell-derived cardiac progenitors.

Targeting transcription in heart failure via CDK7/12/13 inhibition.

Heart failure with reduced ejection fraction (HFrEF) is associated with high mortality, highlighting an urgent need for new therapeutic strategies. As stress-activated cardiac signaling cascades converge on the nucleus to drive maladaptive gene programs, interdicting pathological transcription is a conceptually attractive approach for HFrEF therapy. Here, we demonstrate that CDK7/12/13 are critical regulators of transcription activation in the heart that can be pharmacologically inhibited to improve HFrEF.

Modeling congenital heart disease: lessons from mice, hPSC-based models, and organoids.

Congenital heart defects (CHDs) are among the most common birth defects, but their etiology has long been mysterious. In recent decades, the development of a variety of experimental models has led to a greater understanding of the molecular basis of CHDs. In this review, we contrast mouse models of CHD, which maintain the anatomical arrangement of the heart, and human cellular models of CHD, which are more likely to capture human-specific biology but lack anatomical structure.

Creation of a Proof-of-Concept 3D-Printed Spinal Lateral Access Simulator.

Background Minimally invasive lateral lumbar interbody fusion (LLIF) offers advantages over traditional approaches, providing indirect decompression of neural elements and deformity correction while avoiding many challenges and risks of anterior and posterior approaches. Mastering this technique requires a specialized team, advanced equipment, and sufficient case exposure. Current training is limited to the classic educational model, and alternative training methods such as cadaver labs can be inconvenient, inaccessible, expensive, and incompatible with intraoperative neuromonitoring (IONM) systems.

Transcription factor protein interactomes reveal genetic determinants in heart disease.

Congenital heart disease (CHD) is present in 1% of live births, yet identification of causal mutations remains challenging. We hypothesized that genetic determinants for CHDs may lie in the protein interactomes of transcription factors whose mutations cause CHDs. Defining the interactomes of two transcription factors haplo-insufficient in CHD, GATA4 and TBX5, within human cardiac progenitors, and integrating the results with nearly 9,000 exomes from proband-parent trios revealed an enrichment of de novo missense variants associated with CHD within the interactomes.

Brahma safeguards canalization of cardiac mesoderm differentiation.

Differentiation proceeds along a continuum of increasingly fate-restricted intermediates, referred to as canalization. Canalization is essential for stabilizing cell fate, but the mechanisms that underlie robust canalization are unclear. Here we show that the BRG1/BRM-associated factor (BAF) chromatin-remodelling complex ATPase gene Brm safeguards cell identity during directed cardiogenesis of mouse embryonic stem cells.