Epithelial-Mesenchymal transition-like process transcription factors in pituitary cells

A.DE PAUL; M.I.PEREZ MILLAN; F.MERCOGLIANO; A. SEILICOVICH; M.MARTÍ; S.CAMPER

Congreso; LXIII Reunión de la Sociedad Argentina de Investigación Clínica; 2018

Mutations in PROP1, a key transcription factor of pituitary stem cell differentiation, are the most common known cause of hypopituitarism. The basis of this mechanism is not completely understood. Our goal is to better understand the factors regulating embryonic pituitary progenitor cells. Previously, we determined that PROP1 is essential for stem cells to undergo an epithelial to mesenchymal transition-like (EMT) process necessary for cell migration and differentiation. Here, we conducted RNA-Seq and mass spectrometry experiments using an engineered mouse cell line: pituitary GHFT1 cells expressing biotin-tagged PROP1. Gene expression profiling of GHFT1 PROP1 vs GHFT1 cells revealed that many genes in the extracellular matrix were affected in PROP1-expressing cells, like matrix metalloproteinases, MMP2, 15 and 15, that were up-regulated and disintegrins and metalloproteinases with or without thrombospondin motifs (ADAM and ADAMTS) that were down-regulated. MMPs play key roles in embryonic development and are involved in EMT during the morphogenesis of many tissues. We examined expression of MMP2 during pituitary development in control and Prop1df/df mice. At e12.5, e14.5 and e16.5, MMP2 is normally expressed in the pituitary gland in normal mice and it is almost absent in Prop1 mutant pituitaries. Furthermore, we observed an increase in cell-cell junctions by TEM in P1 pituitaries from Prop1df/df mice. Using immunoprecipitation coupled to mass spectrometry, we identified 93 proteins that specifically interact with PROP1. These proteins were tested for GO biological process enrichment, and two predominant themes were identified: Cell-Cell Adherens Junction and Cell-Cell adhesion. Several genes from these groups of proteins are candidates for involvement in migration and EMT that fails in Prop1 mutants. Altogether these findings contribute to understand the aetiology of hypopituitarism, could lead to improved diagnosis and offer new therapeutic targets to overcome the disease.