Discovery and Characterization of Endometrial Epithelial Messenger Ribonucleic Acids Using the Ovine Uterine Gland Knockout Model¹

TLDR

Prolonged exposure of the developing neonatal ovine uterus to a progestin from birth prevents uterine gland development, producing an adult endometrial phenotype lacking glandular epithelium (the UGKO phenotype). The study compared endometrial tissue from normal and UGKO sheep, using mRNA differential display PCR and suppression subtractive hybridization to isolate differentially expressed epithelial transcripts. The authors identified both known and novel endometrial epithelial mRNAs—including β‑lactoglobulin, alkaline phosphatase, retroviral genes, gp330/megalin, and matrix Gla protein—whose expression varied with the estrous cycle and pregnancy, demonstrating that the UGKO model is a valuable tool for discovering epithelial‑specific genes and providing cDNA resources for genetic mapping and functional studies.

Abstract

Prolonged exposure of the developing neonatal ovine uterus to a progestin from birth prevents uterine gland development and creates an adult endometrial phenotype characterized by the absence of glandular epithelium, the uterine gland knockout (UGKO) phenotype. This study used endometrium from normal and UGKO sheep to identify messenger RNAs (mRNAs) expressed differentially in the endometrial epithelium using the molecular techniques of mRNA differential display PCR (DD-PCR) and suppression subtractive complementary DNA (cDNA) hybridization (SSH). Sequence analyses of DD- and SSH-identified and cloned cDNAs indicated similarity of some to known mRNAs, including β-lactoglobulin, alkaline phosphatase, type B and D endogenous sheep retroviruses, gp330/megalin, matrix Gla protein, and others. Other cDNAs were not similar to any known sequences and are considered novel, although some of these match human expressed sequence tags. In situ hybridization analyses of uteri from cyclic and pregnant ewes indicated that all DD-PCR- and SSH-identified mRNAs were expressed in either the endometrial lumenal and/or glandular epithelium, although some were also expressed in other uterine cell types. Northern and in situ hybridization analyses revealed that patterns of mRNA expression for most clones were affected by the day of the estrous cycle and pregnancy in a manner consistent with regulation by progesterone. Studies demonstrate the utility of the ovine UGKO model as a tool with which to identify known and novel uterine epithelial-specific genes. Cloned cDNAs identified here are expressed sequence tags useful for comparative and physical genetic mapping and may be used to reveal new factors and pathways regulating endometrial function.