Role of dyskerin in oral epithelial homeostasis

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DESCRIPTION (provided by applicant): The candidate has dedicated himself to a career in oral health-related research to complement his training in oral and maxillofacial pathology. He is applying for a K08 Mentored Clinical Scientist Development Award to facilitate protected time for the pursuit of his research activities together with didactic training in Translational Research methodology. During the course of the award period, he will obtain formal instruction, acquire new skills, learn cutting-edge methodologies, and directly benefit from the guidance and expertise of world-class investigators. Under the outstanding mentorship of Drs. Anil Rustgi and Sarah Millar, and the experience and insights of a diverse Advisory Committee, the Career Development Award will ensure that Dr. Alawi can continue his professional development and achieve his goal of becoming an independent investigator. Oral squamous epithelial cells undergo a well-defined differentiation program. To that end, several genetic diseases, including X-linked dyskeratosis congenita (DC), affect the oral mucosal tissues. X-linked DC is caused by mutations in the DKC1 (dyskerin) gene. Oral leukoplakia is one of the most common clinical manifestations, and the appearance of these preneoplastic lesions during childhood and adolescence indicates that loss of normal dyskerin function disrupts oral epithelial homeostasis. However, the mechanisms remain to be elucidated. Dyskerin is required for the biogenesis of ribonucleoproteins that incorporate small non-coding RNA molecules characterized by the H/ACA secondary structure. It is in this capacity that dyskerin contributes to telomerase activity and precursor rRNA processing. However, while both of these cellular processes are repressed during mitosis, we have shown that dyskerin expression peaks during mitosis, the protein localizes to distinct sub-cellular structures in mitotic oral keratinocytes, and acute loss of dyskerin function triggers G2/M arrest and leads to the accumulation of atypical mitoses with multi-polar spindles. We also recently demonstrated that dyskerin depletion reduces the levels of a subset of H/ACA small nucleolar RNA-derived microRNAs (miRNA) and their corresponding precursors. MicroRNAs play critical roles in the maintenance of normal cell homeostasis through regulation of post-transcriptional gene expression, including of genes essential for mitosis. In this hypothesis-driven proposal, we will use novel morphological, biochemical, functional and genetic approaches to determine the mechanisms by which dyskerin and its cognate RNA critically regulate oral epithelial homeostasis. In particular, we will (1) determine the role and mechanism of dyskerin localization during mitosis, (2) determine the role of dyskerin in post-transcriptional gene expression and (3) determine the in vivo effects of dyskerin mutation on oral epithelium using a mouse model of X-linked DC. By elucidating novel functions for dyskerin, identifying the roles of its associated RNA, and by complementing in vitro experiments with in vivo investigations, these studies will lead to a wealth of new knowledge that may result in novel therapeutic strategies for oral leukoplakia and X-linked DC.