Regulators of epidermal growth and differentiation

Project Summary/Abstract Background: The prevailing model of epidermal differentiation is that transcription factors recruit RNA Polymerase II to differentiation gene promoters only upon the induction of differentiation. It is possible that mechanisms downstream of transcription initiation such as transcriptional elongation can have major impacts on regulating epidermal growth and differentiation. We have shown that specific elongation factors such as ELL and ELL2 are necessary for epidermal growth while SPT6 is essential for differentiation through the control of transcription elongation. Objective/hypothesis: This proposal seeks to understand the regulation of epidermal stem and progenitor cell self-renewal and differentiation through transcription elongation. We have found that up to 30% of induced epidermal differentiation genes contain promoter proximal paused RNA polymerase II in stem and progenitor cells. Upon differentiation, specific elongation factors such as SPT6 are necessary to promote the transcriptional elongation of these paused differentiation genes. In stem and progenitor cells there are also elongation factors that promote the transcription of growth and proliferation genes to allow for epidermal renewal. Specific Aims: (1) The role of transcription elongation factors on epidermal growth and differentiation (2) Mechanisms on how elongation factors control epidermal growth and differentiation. Study Design: To study epidermal homeostasis in a more clinically relevant setting, we generate 3-dimensionally intact human skin, containing human epidermal cells (that have been permanently knocked down for transcription elongation factors) in the context of human dermal stroma and basement membrane, regenerated on immune compromised mice. By using this model, we can perform loss of function experiments on the transcription elongation factors in regenerated human skin to characterize their role in epidermal growth and differentiation. We will also use chromatin immunoprecipitations followed by next generation sequencing to determine which genes the elongation factors bind and regulate.