PARENT SESSION
IMPLANTATION AND PREGNANCY - A

Monday, August 2, 2004
10:30 AM–12:30 PM
Buchanan Courtyard

(248) IDENTIFICATION OF A SIGNAL PEPTIDASE EXPRESSED EXCLUSIVELY BY THE UTERINE GLANDS THROUGHOUT PREGNANCY IN THE EWE.

Meyer, Jennifer¹, Gray, Allison¹, Millimaki, Ryan¹, Adelson, David¹, Thomas, Terry², Spencer, Thomas¹, ¹ Texas A&M University, College Station, TX² Texas A&M University, College Station, TX

ABSTRACT- Endometrial glands synthesize and secrete or selectively transport substances into the uterine lumen that support conceptus (embryo/fetus and placental membranes) growth. In the ovine Uterine Gland Knockout (UGKO) model, blastocysts hatch normally but fail to elongate between Days 12 and 14 of pregnancy. A combination of the UGKO sheep model with global gene expression profiling should be useful to elucidate candidate genes regulating peri-implantation conceptus survival and development. An endometrial cDNA library was constructed using a pool of endometrium from Day 14 pregnant ewes. Random clones (n=5,000) were isolated and sequenced. The cDNAs from the clones were PCR amplified and spotted onto a glass slide. This custom cDNA array was used to profile gene expression in endometrium from Day 14 cyclic (C) and pregnant (P) fertile ewes and infertile UGKO ewes. Expression of 176 genes was increased greater than 5-fold in P versus UGKO endometrium, including a number of novel genes such as galectin-15 and signal peptidase (GenBank BC009703). Northern analysis of endometrial total RNA indicated the presence of two mRNAs for signal peptidase (1.2 kb and 0.8 kb). Slot blot hybridization analyses found that steady-state levels of signal peptidase mRNA in the endometrium were low on Days 10 to 16 of the estrous cycle and pregnancy, but increased on Days 18 and 20 of pregnancy (day x status p<0.03). Between Days 20 and 120 of pregnancy, signal peptidase mRNA levels remained high in the intercaruncular endometrium, but were low to undetectable in the placentomes (maternal caruncle and placental cotyledon). In situ hybridization analyses revealed that signal peptidase mRNA was restricted to the endometrial glands during pregnancy. These results indicate that signal peptidase is expressed by the endometrial glands throughout pregnancy and may be involved in cleaving signal peptides prior to secretion into the uterine lumen as components of histotroph. Continued identification and validation of other genes and their functions using this experimental approach will reveal new factors and pathways regulating endometrial function to support conceptus survival, growth and implantation, as well as to provide potential new targets to improve embryo culture and diagnose infertility. Supported by USDA NRI Grant 2001-02259.

KEY WORDS: endometrium, ovine, pregnancy, signal peptidase