ABSTRACT: The molecular and cellular processes required for development, function, and regression of the primate corpus luteum (CL) are poorly defined. We hypothesized that there are dynamic changes in gene expression occurring during the CL lifespan, which represent proteins and pathways critical to its regulation. Therefore, a genomic approach was utilized to systematically identify differentially expressed genes in the rhesus macaque CL during the luteal phase of natural menstrual cycles. CL were collected between days 3-5 (early stage), 7-8 (mid), 10-12 (mid-late), 14-16 (late), or 18-19 (very-late) after the midcycle LH surge. From the early through very-late stages, 3234 transcripts were differentially expressed, with 879 occurring from the early through late stages that encompass the processes of luteinization, maintenance, and functional regression. To characterize gene changes most relevant to these processes, ontology analysis was performed using the list of 879 differentially expressed transcripts. Four main groups of related genes were identified with relevance to luteal physiology including: 1) immune function; 2) hormone and growth factor signaling; 3) steroidogenesis; and 4) prostaglandin biosynthesis, metabolism, and signaling. A subset of genes representing each of the four major categories was selected for validation of microarray results by quantitative real-time PCR. Results in mRNA levels were similar between the two methodologies for 17 of 18 genes. Additionally, protein levels for 3 genes were determined by Western blot analysis to parallel mRNA levels. This database will facilitate the identification of many novel or previously underappreciated pathways that regulate the structure and function of the primate CL. Keywords: time course The sole experimental factor is the stage of the luteal phase when the CL was collected. There were five stages: 1) between days 3-5 post LH-surge (early stage), 2) 7-8 (mid stage), 3) 10-12 (mid-late stage), 4) 14-16 (late stage), and 5) 18-19 (very-late stage). The early CL are undergoing luteinization, the mid are fully functional CL that are at their peak progesterone producing capacity, the mid-late stage is a transitionary period where CL are still producing significant quantities of progesterone but are nearing the time when luteolysis initiates in non-conception cycles, the late stage corresponds to CL undergoing functional regression (cessation of progesterone secretion), and the very-late stage (menses) is when the structural remodeling and apoptosis associated with luteolysis is occurring. Measuring mRNA levels in CL collected during these periods provides a comprehensive analysis of the primate transcriptome throughout CL lifespan. There were 20 biological replicates: n = 4 per stage, 5 stages in total. The early CL were used as the baseline reference for gene expression.
