Tension In Bacteria

Introduction: In vertebrates, the skin is made up of two layers: the outer epidermis and inner dermis. The epidermis, being the outermost layer, functions as a protective barrier between the external environment and the internal organs of the body, thereby protecting the internal organs from external stresses such as pathogens, toxins, water loss, chemical and physical stresses, etc.1 A majority of physical stresses that the epidermis experiences are in the form of spring forces, osmotic pressure, tensional forces, surface tension, sheer stress, etc.. Mechanical forces are generated in part through external physical assaults and in part through dynamics of the internal cytoskeletal machinery like actin, tubulin and intermediate filaments,

These studies subject the cell layers to stretch using one- dimensional stretch and two- dimensional strain devices either uniaxially or biaxially. To study the effect of tension on the cell-cell interactions, techniques like Shear stress, Optical traps, Magnetic force application and magnetic twisting have been used.12 However, these techniques prove to be more useful in in-vitro studies. For the purpose of studying the effect of tension on the zebrafish epidermis in vivo, a paradigm was developed in the lab, which constituted injecting a measured volume of biologically and chemically inert mineral oil into the hindbrain ventricle of the zebrafish embryos at 24 hpf (hours post fertilization). This causes the ventricle to expand, thereby stretching the epidermis over the oil drop. This stretch creates a tension in the epidermis, as it now has to cover a larger area. This paradigm allows us to track changes in the developing bilayered epidermis in vivo over

In the lab, it has been shown that under mechanical stress, the epidermal cells show an increase in the cell cross-sectional area, increased fragmentation of apical microridges, and increased cell proliferation. The cell cross-sectional area and microridge architecture recover as proliferation continues. In the study conducted by Renuka et al. 2016, aPKC morphants show a premature elongation of microridges, where the wildtype ridge length at 27 hpf corresponded to ridge length at 20-22hpf in the has mutants. This increase in length occurs due to an increase in the fusion of shorter microridges, which can be accounted for by the increased crosslinking of actin by the higher levels of phosphomyosin that are localized to the apical domain. Thus, the has mutants have a less fragmented and precociously stable microridge pattern.8 . Therefore, to understand the role of microridge dynamics in allowing the epidermis to sustain the increased mechanical stress, I will knockdown aPKC in zebrafish embryos using morpholinos that competitively block translation14. I will subject these embryos to mechanical stress using the oil injection paradigm. when the epithelial tissue is subjected to mechanical stretch by oil injection in the hind-brain ventricle, the area that the tissue has to cover significantly increases. This increase can amount to an increase in the