The Role of FOXK1 in Keratinocyte Differentiation

Abstract

Cell differentiation is the process by which cells become more specialised to perform a specific function. Many intrinsic and extrinsic factors, such as signal transduction events and the surrounding environment, interplay to regulate this process. Previous work in the lab identified that loss of Rnd3 (a member of the Rho family of small GTPases) expression blocked epidermal keratinocyte differentiation suggesting that Rnd3 plays an important role in skin biology. Proteomic data identified the FOXK1 transcription factor, a member of the forkhead box transcription factors family, as one of several proteins with significantly altered expression in Rnd3 knockdown cells. This project aimed to identify whether FOXK1 is important for keratinocyte differentiation. Culturing keratinocytes in low Ca2+ media suppresses differentiation and switching them to high Ca2+ medium induces differentiation. Under these conditions, FOXK1 expression was increased during differentiation, however, knocking out FOXK1 did not prevent differentiation suggesting that whilst FOXK1 may be required for the expression of some differentiation-specific genes, it is not necessary for the initiation of differentiation. Furthermore, EdU-stained FOXK1 knockout cells were found to be 50% less proliferative than wild type cells. Next-generation RNA-sequencing (RNA-Seq) revealed that FOXK1 knockout cells had upregulated differentiation genes and downregulated cell proliferation and division genes, suggesting that FOXK1 is required for the proper maintenance of cellular proliferation and differentiation.