Abstract
Legend: The epithelium of the adult uterus consists of a luminal epithelium (LE) that is negative for the Forkhead box A2 (FOXA2) transcription factor and a glandular epithelium (GE) that is positive for FOXA2 and required for fertility. We discovered that gland formation (adenogenesis) within the neonatal bovine uterus was associated with the differentiation of islands of LE cells into FOXA2+ cells (LE to GE specification). This process precedes bud formation and tubulogenesis. The LE to GE specification does not involve cellular proliferation (based on MKI67 marker). The LE to GE specification may be the initial step in gland formation that is followed by rupture of the basement membrane and penetration of the underlying stroma by FOXA2+ cells.