Transcriptomic and Single-Cell Analysis of the Murine Parotid Gland.

The salivary complex of mammals consists of 3 major pairs of glands: the parotid, submandibular, and sublingual glands. While the 3 glands share similar functional properties, such as saliva secretion, their differences are largely based on the types of secretions they produce. While recent studies have begun to shed light on the underlying molecular differences among the glands, few have examined the global transcriptional repertoire over various stages of gland maturation. To better elucidate the molecular nature of the parotid gland, we have performed RNA sequencing to generate comprehensive and global gene expression profiles of this gland at different stages of maturation. Our transcriptomic characterization and hierarchical clustering analysis with adult organ RNA sequencing data sets has identified a number of molecular players and pathways that are relevant for parotid gland biology. Moreover, our detailed analysis has revealed a unique parotid gland-specific gene signature that may represent important players that could impart parotid gland-specific biological properties. To complement our transcriptomic studies, we have performed single-cell RNA sequencing to map the transcriptomes of parotid epithelial cells. Interrogation of the single-cell transcriptomes revealed the degree of molecular and cellular heterogeneity of the various epithelial cell types within the parotid gland. Moreover, we uncovered a mixed-lineage population of cells that may reflect molecular priming of differentiation potentials. Overall our comprehensive studies provide a powerful tool for the discovery of novel molecular players important in parotid gland biology.

Contribution of DNA methylation to the expression of FCGRT in human liver and myocardium.

FcRn mediates recycling and transcytosis of IgG and albumin in various cell types. The MHC-class-I-like protein of the FcRn heterodimer is encoded by FCGRT. Few determinants of variable FCGRT expression in humans have been identified so far. In this study, we investigated the presence of DNA methylation in regulatory regions of FCGRT in samples of human liver and myocardium tissue, and we examined the impact of FCGRT methylation on FcRn expression in model cell lines. Quantitative DNA methylation analysis of the FCGRT locus revealed differentially methylated regions in DNA from liver and myocardium. Methylation status in individual CpG sites correlated with FCGRT mRNA expression. Data from model cell lines suggest that differential methylation in the -1058 to -587 bp regulatory region of FCGRT contributes to FcRn expression. Chromatin immunoprecipitation assays indicate that CpG site methylation impacts the binding of the methylation sensitive transcription factors Zbtb7a and Sp1. This study provides a foundation to further define the contribution of epigenetic factors during the control of FcRn expression and IgG traffic in human tissues.