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Purpose The aim of this study is to describe the incidence of Acute Kidney Injury (AKI) amongst patients admitted to the Intensive Care Unit (ICU) with COVID-19. In addition we aim to detail the range of Renal Replacement Therapy (RRT) modalities offered to these patients (including peritoneal dialysis - PD - and intermittent haemodialysis - IHD) in order to meet demand during pandemic conditions. Materials and methods Single-centre retrospective case note review of adult patients with confirmed COVID-19 admitted to ICU. Results Amongst 136 patients without a prior history of End Stage Kidney Disease (ESKD), 108 (79%) developed AKI and 63% of admitted patients received RRT. Due to resource limitations the range of RRT options were expanded from solely Continuous Veno-Venous HaemoDiaFiltration (CVVHDF - our usual standard of care) to include PD (in 35 patients) and IHD (in 15 patients). During the study period the proportion of RRT provided within ICU as CVVHDF fell from 100% to a nadir of 39%. There were no significant complications of either PD or IHD. Conclusions During periods of resource limitations PD and IHD can safely be used to reduce dependence on CVVHDF in select patients with AKI secondary to COVID-19., Highlights • AKI frequently complicates COVID-19 in patients admitted to ICU. • Large numbers of patients and high rates of AKI leads to great demand for RRT. • In selected patients PD and IHD can supplement CRRT in meeting this demand. • PD and IHD can be implemented rapidly and safely through a collaborative approach.

Using the zebrafish neural tube as a model, we uncover thein vivomechanisms allowing the generation of two opposing apical epithelial surfaces within the centre of an initially unpolarised, solid organ. We show that NOK/Pals1/Mpp5a and Rab11a play a dual role in coordinating the generation of ipsilateral junctional belts whilst simultaneously releasing contralateral adhesions across the centre of the tissue. We show that Nok and Rab11a mediated resolution of cell-cell adhesions are both necessary for midline lumen opening and contribute to later maintenance of epithelial organisation. We propose these roles for both Nok and Rab11a operate through the transmembrane protein Crumbs. In light of a recent conflicting publication, we also clarify that the junction remodelling role of Nok is not specific to dividing cells.

Using the zebrafish neural tube as a model, we uncover the in vivo mechanisms allowing the generation of two opposing apical epithelial surfaces within the centre of an initially unpolarised, solid organ. We show that Mpp5a and Rab11a play a dual role in coordinating the generation of ipsilateral junctional belts whilst simultaneously releasing contralateral adhesions across the centre of the tissue. We show that Mpp5a- and Rab11a-mediated resolution of cell-cell adhesions are both necessary for midline lumen opening and contribute to later maintenance of epithelial organisation. We propose that these roles for both Mpp5a and Rab11a operate through the transmembrane protein Crumbs. In light of a recent conflicting publication, we also clarify that the junction-remodelling role of Mpp5a is not specific to dividing cells.

In vitro, developing neurons progress through well-defined stages to form an axon and multiple dendrites.In vivo, neurons are derived from progenitors within a polarised neuroepithelium and it is not clear how axon initiation observedin vitrorelates to what occurs in a complex, three-dimensionalin vivoenvironment. Here we show that the position of axon initiation in embryonic zebrafish spinal neurons is extremely consistent across neuronal sub-types. We investigated what mechanisms may regulate axon positioningin vivoand found that microtubule organising centres are located distant from the site of axon initiation in contrast to that observedin vitro, and that microtubule plus-ends are not enriched in the axon during axon initiation. F-actin accumulation precedes axon formation and nascent axons form but are not stabilised in the absence of microtubules. Laminin depletion removes a spatial cue for axon initiation but axon initiation remains robust.

In the vertebrate central nervous system, groups of functionally-related neurons, including cranial motor neurons of the brainstem, are frequently organised as nuclei. The molecular mechanisms governing the emergence of nuclear topography and circuit function are poorly understood. Here we investigate the role of cadherin-mediated adhesion in the development of zebrafish ocular motor (sub)nuclei. We find that developing ocular motor (sub)nuclei differentially express classical cadherins. Perturbing cadherin function in these neurons results in distinct defects in neuronal positioning, including scattering of dorsal cells and defective contralateral migration of ventral subnuclei. In addition, we show that cadherin-mediated interactions between adjacent subnuclei are critical for subnucleus position. We also find that disrupting cadherin adhesivity in dorsal oculomotor neurons impairs the larval optokinetic reflex, suggesting that neuronal clustering is important for co-ordinating circuit function. Our findings reveal that cadherins regulate distinct aspects of cranial motor neuron positioning and establish subnuclear topography and motor function.

Tissue internalisation is a key morphogenetic mechanism by which embryonic tissues generate complex internal organs and a number of studies of epithelia have outlined a general view of tissue internalisation. Here we have used quantitative live imaging and mutant analysis to determine whether similar mechanisms are responsible for internalisation in a tissue that apparently does not have a typical epithelial organisation - the zebrafish neural plate. We found that although zebrafish embryos begin neurulation without a conventional epithelium, medially located neural plate cells adopt strategies typical of epithelia in order to constrict their dorsal surface membrane during cell internalisation. Furthermore, we show that Myosin-II activity is a significant driver of this transient cell remodeling which also depends on Cdh2 (N-cadherin). Abrogation of Cdh2 results in defective Myosin-II distribution, mislocalised internalisation events and defective neural plate morphogenesis. Our work suggests Cdh2 coordinates Myosin-II dependent internalisation of the zebrafish neural plate.

In contrast to conventional human pluripotent stem cells (hPSC) that are related to post-implantation embryo stages, naïve hPSC exhibit features of pre-implantation epiblast. Naïve hPSC are established by resetting conventional hPSC, or are derived from dissociated embryo inner cell masses. Here we investigate conditions for transgene-free reprogramming of human somatic cells to naïve pluripotency. We find that tankyrase inhibition promotes RNA-mediated induction of naïve pluripotency. We demonstrate application to independent human fibroblast cultures and endothelial progenitor cells. We show that induced naïve hPSC can be clonally expanded with a diploid karyotype and undergo somatic lineage differentiation following formative transition. Induced naïve hPSC lines exhibit distinctive surface marker, transcriptome, and methylome properties of naïve epiblast identity. This system for efficient, facile, and reliable induction of transgene free naïve hPSC offers a robust platform, both for delineation of human reprogramming trajectories and for evaluating the attributes of isogenic naïve versus conventional hPSC.

Tissue internalisation is a key morphogenetic mechanism by which embryonic tissues generate complex internal organs and a number of studies of epithelia have outlined a general view of tissue internalisation. Here we have used quantitative live imaging and mutant analysis to determine whether similar mechanisms are responsible for internalisation in a tissue that apparently does not have a typical epithelial organisation – the zebrafish neural plate. We found that although zebrafish embryos begin neurulation without a conventional epithelium, medially located neural plate cells adopt strategies typical of epithelia in order to constrict their dorsal surface membrane during cell internalisation. Furthermore, we show that Myosin-II activity is a significant driver of this transient cell remodeling which also depends on Cdh2 (N-cadherin). Abrogation of Cdh2 results in defective Myosin-II distribution, mislocalised internalisation events and defective neural plate morphogenesis. Our work suggests Cdh2 coordinates Myosin-II dependent internalisation of the zebrafish neural plate.

Background During the initial stages zebrafish neurulation, neural plate cells undergo highly coordinated movements before they assemble into a multicellular solid neural rod. We have previously identified that the underlying mesoderm is critical to ensure such coordination and generate correct neural tube organization. However, how intertissue coordination is achieved in vivo during zebrafish neural tube morphogenesis is unknown. Results In this work, we use quantitative live imaging to study the coordinated movements of neural ectoderm and mesoderm during dorsal tissue convergence. We show the extracellular matrix components laminin and fibronectin that lie between mesoderm and neural plate act to couple the movements of neural plate and mesoderm during early stages of neurulation and to maintain the close apposition of these two tissues. Conclusions Our study highlights the importance of the extracellular matrix proteins laminin and libronectin in coupling the movements and spatial proximity of mesoderm and neuroectoderm during the morphogenetic movements of neurulation. Developmental Dynamics 245:580-589, 2016. © 2016 Wiley Periodicals, Inc.

SummaryWe use the transparency of zebrafish embryos to reveal thede novogeneration of a simple squamous epithelium and identify the cellular architecture in the epithelial transition zone that ties this squamous epithelium to the columnar neuroepithelium within the embryo’s brain. The simple squamous epithelium of the rhombencephalic roof plate is pioneered by distinct mesenchymal cells at the dorsal midline of the neural tube. Subsequently a progenitor zone is established at the interface between columnar epithelium of the rhombic lip and the expanding squamous epithelium of the roof plate. Surprisingly this interface consists of a single progenitor cell type that we have named the veil cell. Veil cells expressgdf6aand constitute a lineage restricted stem zone that generates the squamous roof plate by direct transformation and asymmetrically fated divisions. Experimental restriction of roof plate expansion leads to extrusion of veil cell daughters and squamous cells, suggesting veil cell fate is regulated by the space available for roof plate growth.

Summary We demonstrate the utility of the phytochrome system to rapidly and reversibly recruit proteins to specific subcellular regions within specific cells in a living vertebrate embryo. Light-induced heterodimerization using the phytochrome system has previously been used as a powerful tool to dissect signaling pathways for single cells in culture but has not previously been used to reversibly manipulate the precise subcellular location of proteins in multicellular organisms. Here we report the experimental conditions necessary to use this system to manipulate proteins in vivo. As proof of principle, we demonstrate that we can manipulate the localization of the apical polarity protein Pard3 with high temporal and spatial precision in both the neural tube and the embryo’s enveloping layer epithelium. Our optimizations of optogenetic component expression and chromophore purification and delivery should significantly lower the barrier for establishing this powerful optogenetic system in other multicellular organisms., Graphical Abstract, Highlights • The phytochrome system has been optimized for use within multicellular organisms • Protein recruitment can be tightly controlled to a specific subcellular region • Protein recruitment occurs with high binding and reversal kinetics • The subcellular localization of the apical polarity protein Pard3 is manipulated, The phytochrome system is a powerful tool that is used to manipulate protein localization. Here, Buckley et al. optimize the phytochrome system in live zebrafish embryos and demonstrate rapid and reversible protein recruitment to specific subcellular regions within specific cells, at a high spatial and temporal resolution.