Transcriptional regulatory Mechanisms of Salivary gland Regeneration in a defined genetic model

About This Grant

PROJECT SUMMARY Salivary gland (SG) regeneration involves a coordinated interplay of self-renewal, cell fate determination, and differentiation programs in stem/progenitor epithelial cells. Identifying the transcriptional and signaling networks that govern these complex processes is crucial for understanding the underlying molecular mechanisms driving cellular regeneration. By leveraging extensive genomic and epigenomic datasets generated by our group and others, we have identified master transcription factors (TFs) that are enriched and highly expressed in the mouse SG. Based on our preliminary results from a well-defined ductal ligation model of SG regeneration we hypothesize that Six1 functions as a key transcriptional regulator of stem/progenitor cell activity during gland regeneration. We further hypothesize that Six1 directs distinct gene expression programs necessary for the differentiation of specialized SG cell populations and in shaping the dynamic chromatin landscape crucial for cell fate decisions in the pivotal regeneration stages. Thus, we posit that examination of the Six1-driven gene and signaling regulatory networks, particularly in the context of epigenomics, and regeneration after injury, is a key step towards advancing our understanding of SG biology. To achieve this, we propose to use a Six1 conditional knockout (cKO) mouse model and a systems biology approach to pursue two major areas of interest. First, we will use Six1cKO animals to assess the relative contribution of Six1+ve cells during SG regeneration. Furthermore, we will probe mechanistically how Six1 shapes the myriad cellular identities and fate trajectories within the 3-D ecosystem of the SG by performing single-cell (sc) RNA-sequencing (Aim1). Secondly, we will examine the cell-type specific molecular mechanism by which Six1 acts as a pioneer factor to modulate the epigenome and gene expression programs during specific stages of regeneration following ductal ligation in the SG utilizing scATAC-seq and scCUT&Tag with histone markers for active regulatory elements (Aim 2). Collectively, our proposed studies will not only reveal the role of Six1 in governing regeneration programs to maintain and restore the distinct cellular subtypes the SG, but also enrich existing molecular paradigms of cell- specific transcriptional regulatory networks and signaling pathways. Long term, such knowledge will impact therapeutic interventions in human patients who suffer from SG dysfunction.