Defense Date


Document Type


Degree Name

Doctor of Philosophy


Human Genetics

First Advisor

Amanda J. Dickinson


The desmosome is one of the major cell adhesion junctions found in the epithelia, heart, and hair follicle. Described as a “rivet” that hold cells together, it provides these tissues with the integrity to withstand the tremendous forces they face in everyday life. Defects in this junction can lead to devastating diseases where patients are susceptible to skin infections and cardiovascular defects. Limited treatments exist for diseases of the desmosome, and strategies do not target all symptoms. Therefore, delineating the function and regulation of desmosomes is of paramount importance for the development of prevention and treatment strategies. The Xenopus laevis has been utilized for the study of embryonic development and tissue movements. This study takes advantage of the frog model to study a key desmosomal protein, desmoplakin (Dsp), in the epidermal development of the embryo. First, Xenopus embryonic epidermis has junctional desmosomes as early as the blastula stages. Desmosomes numbers per junction increase as the embryo develops. Dsp is present in many epidermally-derived structures in the embryo at varying levels. Xenopus embryos deficient in desmoplakin have phenotypic defects in epidermal structures and the heart, mimicking mammalian models. Embryos with reduced Dsp exhibit an increased susceptibility to epidermal damage under applied mechanical forces. Assays also reveal a potential role for desmosomes in radial intercalation, a process through which cells move from the inner to the outer epidermal layers. Embryos with reduced Dsp exhibit a slight reduction in intercalation and defects in intercalating cell types, including multiciliated cells and small secretory cells. Finally, c-Jun N-terminal kinase (JNK) may have a potential role in the regulation of desmosome assembly and adhesion. Embryos with deficient Dsp display a partial recovery of mechanical integrity when treated with a JNK inhibitor.


© Navaneetha Krishnan Bharathan

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