Using Optogenetics to Investigate the Shared Mechanisms of Apical-Basal Polarity and Mitosis.

The initiation of apical-basal (AB) polarity and the process of mitotic cell division are both characterised by the generation of specialised plasma membrane and cortical domains. These are generated using shared mechanisms, such as asymmetric protein accumulation, Rho GTPase signalling, cytoskeletal reorganisation, vesicle trafficking, and asymmetric phosphoinositide distribution. In epithelial tissue, the coordination of AB polarity and mitosis in space and time is important both during initial epithelial development and to maintain tissue integrity and ensure appropriate cell differentiation at later stages.

Apical-basal polarity and the control of epithelial form and function.

Epithelial cells are the most common cell type in all animals, forming the sheets and tubes that compose most organs and tissues. Apical-basal polarity is essential for epithelial cell form and function, as it determines the localization of the adhesion molecules that hold the cells together laterally and the occluding junctions that act as barriers to paracellular diffusion. Polarity must also target the secretion of specific cargoes to the apical, lateral or basal membranes and organize the cytoskeleton and internal architecture of the cell.

Coordinated assembly and release of adhesions builds apical junctional belts during polarisation of an epithelial tube.

Using the zebrafish neural tube as a model, we uncover the 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.

Optogenetic Control of Subcellular Protein Location and Signaling in Vertebrate Embryos.

This chapter describes the use of optogenetic heterodimerization in single cells within whole-vertebrate embryos. This method allows the use of light to reversibly bind together an "anchor" protein and a "bait" protein. Proteins can therefore be directed to specific subcellular compartments, altering biological processes such as cell polarity and signaling.

Discharge Planning: Screening Older Patients for Multidisciplinary Team Referral.

The objective was to determine whether the Elders Risk Assessment Index can predict multi-disciplinary team referral of older patients (≥ 65 years) in Emergency Department same-day discharges. The study identified 1,376 qualifying individuals from a regional New Zealand hospital database. Of these, 12.

Reversible Optogenetic Control of Subcellular Protein Localization in a Live Vertebrate Embryo.

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.

Establishing the plane of symmetry for lumen formation and bilateral brain formation in the zebrafish neural rod.

The lumen of the zebrafish neural tube develops precisely at the midline of the solid neural rod primordium. This process depends on cell polarisation and cell rearrangements, both of which are manifest at the midline of the neural rod. The result of this cell polarisation and cell rearrangement is an epithelial tube that has overt mirror-symmetry, such that cell morphology and apicobasal polarisation are mirrored across the midline of the neural tube.

Mirror-symmetric microtubule assembly and cell interactions drive lumen formation in the zebrafish neural rod.

By analysing the cellular and subcellular events that occur in the centre of the developing zebrafish neural rod, we have uncovered a novel mechanism of cell polarisation during lumen formation. Cells from each side of the neural rod interdigitate across the tissue midline. This is necessary for localisation of apical junctional proteins to the region where cells intersect the tissue midline.

Drug reprofiling using zebrafish identifies novel compounds with potential pro-myelination effects.

Treatment of the autoimmune demyelinating disease multiple sclerosis (MS) requires therapies that both limit and repair damage. While several immunomodulatory treatments exist to limit damage there are currently no treatments that promote the regenerative process of remyelination. A rapid way of screening potential pro-remyelination compounds is therefore required.

Temporal dynamics of myelination in the zebrafish spinal cord.

Knowledge of the precise timing of myelination is critical to the success of zebrafish-based in vivo screening strategies for potential remyelination therapies. This study provides a systematic review of the timing of myelination in the zebrafish spinal cord and a critique of techniques by which it may be accurately assessed. The onset of myelination was found to be 3 days postfertilization (d.

Zebrafish myelination: a transparent model for remyelination?

There is currently an unmet need for a therapy that promotes the regenerative process of remyelination in central nervous system diseases, notably multiple sclerosis (MS). A high-throughput model is, therefore, required to screen potential therapeutic drugs and to refine genomic and proteomic data from MS lesions. Here, we review the value of the zebrafish (Danio rerio) larva as a model of the developmental process of myelination, describing the powerful applications of zebrafish for genetic manipulation and genetic screens, as well as some of the exciting imaging capabilities of this model.