Transcriptional Co-Regulators in Epidermis

PROJECT SUMMARY/ABSTRACT Although the epidermis is composed of morphologically distinct layers, single-cell RNA-seq experiments indicate that epidermal differentiation does not progress in discrete steps at a transcript level but is instead continuous and gradual. Consistent with this notion, we identified a large population of basal-to-spinous transition cells that reside in the basal and first spinous cell layers. These transition cells are found throughout the lifetime of the mouse and in the adult human palmoplantar and non-palmoplantar epidermis. Our hypothesis is that the presence of these transition cells does not reflect an ineffectiveness in switching from basal to spinous gene- regulatory programs. On the contrary, we propose that basal-to-spinous cells are actively maintained through a specific gene-regulatory program. We will use single-cell and spatial transcriptomics approaches to study the cellular composition, gene expression, and predicted function and cell-cell signaling in the P0 epidermis from mice knocked out for transcription factors whose expression peaks in transition cells. We will use single-nuclear ATAC-seq with single-nuclear RNA-seq to map changes in open chromatin across cell states, including in basal- to-spinous transition states. We will also define transcription factor binding and histone modifications in sorted epidermal cells from distinct differentiation stages. We will then use computational modeling to define the underlying gene regulatory networks and to inform further functional testing on the role of signaling pathways and transcription factors in maintaining the basal-to-spinous transition cell state. This work is significant and innovative because it addresses a recently recognized cell state in epidermal differentiation, basal-to-spinous transition cells, which have not been investigated.