Epidermis Development : Building a Barrier with Cells

Organ systems are functional units, which perform specialised tasks that are essential for the survival of an organism. Organs are formed of various tissues, which in turn are formed of cells. The functioning of any organ system depends upon the proper organisation of its components. During development, in a process termed as morphogenesis- meaning creation of the shape- cells collectively form tissues, which then give rise to an organ.  During tissue morphogenesis, cells acquire specific shapes and adhere to each other to form sheets. This sheet like architecture is either retained or it may acquire new shapes such as tubes, ellipses, rods, etc, which are essential for the functioning of a particular organ. Thus, formation of cell adhesion complexes and acquisition of cell shapes are the two most important processes that regulate tissue morphogenesis. We are looking at these two processes in the context of the epidermal morphogenesis. Epidermis is the outermost tissue of the skin. It is a multilayered sheet of cells, which acts as a barrier to prevent the loss of body fluids to the surroundings and protects the internal organs from pathogenic invasion. Thus, it helps to maintain the milieu interior of an organism. We are using zebrafish, an aquatic vertebrate, as a model to understand the molecular mechanisms involved in the maintenance of cell size, cell shape and cell adhesion in the epidermis. I will share with you our previous results, which indicate the role of lethal giant larvae 2- a cell polarity regulator – in the maintenance of epidermal cell adhesion and integrity. I will then present our current results, which suggest that the molecular motor Myosin Vb is involved in regulating cell size in the epidermis. Our results further indicate that epidermal cell size plays important role in the maintenance of tissue homeostasis and that the epidermis maintains a dynamic balance between the cell size and cell number to maintain its integrity.