Lef‐1 is Required for Proper Cell Cycle Progression in Airway Basal Cells

Abstract

The surface airway epithelium (SAE) is a pseudostratified layer of cells found within the mammalian airway, and serves as a barrier between the environment and the rest of the body. Its function is crucial for proper respiration and innate immunity. At homeostasis the SAE has very low cellular turnover, yet has the capacity to regenerate itself after injury or infection at an astonishingly fast rate. This is due primarily to the population of resident stem cells found within the SAE called basal cells. Though much work has been done to identify the molecular mechanisms that govern basal cell proliferation, migration, and differentiation, many questions still remain.The transcription factor Lymphoid Enhancer Binding Factor 1 (Lef‐1) is a Wnt effector protein expressed in stem cell populations in various epithelial tissues, including the developing lung. Our lab has shown that overexpression of Lef‐1 in primary airway stem cell cultures leads to increased proliferation and migration. Additionally, Lef‐1 is required for the development of airway submucosal glands (SMGs), epithelial structures that are continuous with the SAE. However, it is not known if Lef‐1 plays a role in basal cell function. Therefore, we sought to determine the effects of Lef‐1 deletion in basal cells. Though its expression in basal cells is almost undetectable on a population‐wide scale, deletion of Lef‐1 from primary mouse basal cells severely decreases their ability to proliferate in culture, and skews them more toward a secretory club cell fate. Lef‐1 deletion leads to a loss in DNA damage response (DDR) gene expression, including Tp73, Rad51, and Chek1. Lef‐1 knockout basal cells tend to stall in the cell cycle at the G1/S transition. Together these studies indicate an important role for Lef‐1 in basal cell replication and proliferation.Support or Funding InformationUniversity of Iowa Molecular Medicine ProgramUniversity of Iowa Department of Anatomy & Cell Biology Funding: 2R01 DK047967