Protein expression and localization of receptor (chemosensory) transporter protein 4 in the endometrium during early pregnancy in sheep and cattle

• Published in: Journal of animal science Vol. 94; p. 102
• Main Authors: Wilson, K S, Gifford, J A Hernandez, Ott, T L, Gifford, C A
• Format: Journal Article
• Language: English
• Published: Champaign Oxford University Press 01-10-2016
• Subjects: Animal reproduction; Antigens; Bovidae; Cattle; Chemoreception; Corpus luteum; Cross-sections; Endometrium; Epithelium; Fluorescence; Horseradish peroxidase; Immune serum; Immune system; Immunization; Immunofluorescence; Immunoglobulin G; Interferon; Livestock; Localization; mRNA; Ovis aries; Peroxidase; Pregnancy; Protein expression; Protein transport; Proteins; Reproduction; Sheep; Stroma; Uterus
• ISSN: 0021-8812; 1525-3163
• DOI: 10.2527/jam2016-0216

Reproduction in domestic ruminants continues to challenge efficiency in livestock operations. During early pregnancy, the conceptus produces a unique type I interferon, interferon- tau (IFNT), which acts both locally and systemically to regulate IFN-stimulated genes (ISG) in the maternal uterus and circulating immune cells. Previous work demonstrated that mRNA levels for receptor (chemosensory) transporter protein-4 (RTP4) was regulated by pregnancy in peripheral immune cells, the endometrium, and corpus luteum. Receptor transporter protein-4 belongs to a class of G protein coupled receptor transporters, but the function(s) of RTP4 in reproduction remains unclear. Though, mRNA levels for RTP4 are spatially and temporally regulated during early pregnancy in ruminants, there is no information regarding RTP4 protein expression. The objective of the current experiment was to evaluate RTP4 protein expression and localization in the endometrium during early pregnancy in cattle and sheep. A rabbit was immunized using 18 AA in an antigenic region of the amino terminus of RTP4. Rabbit serum was collected pre-immunization and at sacrifice (immune serum). Cross-sections of a D15 pregnant ewe were incubated with pre-immune serum and immune serum (1:600 primary antibody concentration), and protein presence was detected after incubation with biotinylated anti-rabbit IgG and horseradish peroxidase development. No signal was detected for pre-immunized serum, while immune serum exhibited a robust signal in the luminal and glandular epithelium and in the stromal compartments. In the second experiment, cross-sections from D17 pregnant and cyclic Holstein heifers were utilized for immunofluorescence detection of RTP4 protein. Pre-immune serum showed no fluorescence, but immune serum exhibited strong fluorescence in the luminal epithelium, glandular epithelium, and stroma during pregnancy. Interestingly, previous work using in situ hybridization did not detect a presence of RTP4 mRNA in the luminal epithelium, but the RTP4 protein was clearly expressed in the luminal epithelium in the current experiment. These results demonstrate that RTP4 protein is expressed in the uterus and is regulated by pregnancy. Because RTP4 protein is both expressed in maternal tissues and regulated by pregnancy, it seems likely that RTP4 plays a role in establishment of pregnancy in domestic ruminants.