Salivary gland differentiation and functionality relies on the production and secretion of saliva. Mucous, produced mainly by the sublingual glands (SLGs), confers viscous and antiseptic properties on saliva. Mucin glycoproteins are the major constituent of mucous, essential for the formation of mucosal barriers. Hyposecretion of mucins by the SLGs results in xerostomia, characterized by difficulty in phonation and deglutition, mucosal ulcerations, and an increase in the frequency of dental caries. One of the major contributors to xerostomia is an autoimmune disorder known as Sjogren's Syndrome which affects multiple body organs, most notably the salivary and lacrimal glands. NFS-sId mice, a model for Sjogren's Syndrome, display delayed SLG differentiation noted by neonatal mucin-deficiencies, specifically the major mucin product of mouse SLGs, Muc19. Interestingly, our laboratory has confirmed a function for the chromatin- remodeling protein CHD1 in regulating Muc19 expression. This project is designed to further investigate the molecular mechanisms that govern mucin production by the SLGs through the scope of CHD1 and its interactors, relating these findings to the development of novel therapeutic targets for re-activation of mucin production. To accomplish this, the following specific aims will be addressed:
Aim 1 : Compare levels of CHD1 and Mud9 expression, CHD1 protein levels, and the physical presence of CHD1 on the Muc19 promoter and transcribed regions, in NFS-sId and NFS-N (control) mice.
Aim 2 : Investigate the possibilities that the method of Muc19 gene regulation by CHD1 is occurring at the transcriptional elongation and/or alternative-splicing level. NFS-sId and control NFS-N mice will be utilized for all experiments. Gene expression and immunoblotting assays, combined with in vivo immunoprecipitation experiments, will shed light on the influence of quantity, localization, and partnership of CHD1 and its interactors on the expression, and subsequent production, of Muc19, while additional in vivo DNA-protein interaction studies, combined with an investigation of Muc19 transcript variants will allow inferences on the specific mechanism of Muc19 gene regulation in SLGs. The gene-regulatory mechanisms that control mucin production in the SLG remain poorly understood. Knowledge gained through the completion of this project will enhance the understanding of the epidemiology related to the hyposecretion of mucins, such as that which occurs in those afflicted with Sjogren's Syndrome. Also, novel therapeutic targets aimed at re-activation of SLG functionality could be identified.
