Analysis of gene expression in the bovine corpus luteum through generation and characterisation of 960 ESTs

Abstract

To gain new insights into gene identity and gene expression in the bovine corpus luteum (CL) a directionally cloned CL cDNA library was constructed, screened with a total CL cDNA probe and clones representing abundant and rare mRNA transcripts isolated. The 5V-terminal DNA sequence of 960 cDNA clones, composed of 192 abundant and 768 rare mRNA transcripts was determined and clustered into 351 non-redundant expressed sequence tag (EST) groups. Bioinformatic analysis revealed that 309 (88%) of the ESTs showed significant homology to existing sequences in the protein and nucleotide public databases. Several previously unidentified bovine genes encoding proteins associated with key aspects of CL function including extracellular matrix remodelling, lipid metabolism/steroid biosynthesis and apoptosis, were identified. Forty-two (12%) of the ESTs showed homology with human or with other uncharacterised ESTs, some of these were abundantly expressed and may therefore play an important role in primary CL function. Tissue-specificity and temporal CL gene expression of selected clones previously unidentified in bovine CL tissue was also examined. The most interesting finds indicated that mRNA encoding squalene epoxidase was constitutively expressed in CL tissue throughout the oestrous cycle and 7-fold down-regulated ( P < 0.05) in late luteal tissue, concomitant with the disappearance of systemic progesterone, suggesting that de novo cholesterol biosynthesis plays an important role in steroidogenesis. The mRNA encoding the growth factor, insulin-like growth factor-binding protein-related protein 1 (IGFBP-rP1), remained constant during the oestrous cycle and was 1.8-fold up-regulated ( P < 0.05) in late luteal tissue implying a role in CL regression. D

Insulin-Like Growth Factor System in Cancer: Novel Targeted Therapies

“…IGFBP-related protein 1 (or IGFBP-7) has been found to have an important role in the female reproductive system. It was implicated in human endometrial receptivity, folliculogenesis as well as growth, development, and regression of the corpus luteum in higher mammals [ 87 – 89 ]. Other studies showed that it could induce apoptosis in M12 prostate cancer cell line [ 90 ].…”

Circulating IGF-binding protein 7 (IGFBP7) levels are elevated in patients with endometriosis or undergoing diabetic hemodialysis

“…At present, the biological functions of IGFBP7 are unclear. While it is expressed in a wide variety of human tissues, including gut [ 4 ], it is notably abundant in female reproductive organs such as the mature follicle [ 5 ], the corpus luteum [ 6 ], and the uterus [ 7 , 8 ]. IGFBP7 is present in uterine glandular epithelial cells and stromal cells, particularly during the secretory phase of the menstrual cycle, and IGFBP7 mRNA levels in late secretory stage are approximately 150-fold higher than in the proliferative stage [ 7 ].…”

Inhibitory effect of insulin-like growth factor-binding protein-7 (IGFBP7) on in vitro angiogenesis of vascular endothelial cells in the rat corpus luteum

“…IGFBP7 is ubiquitously expressed in normal tissues and implicated in diverse physiological process including proliferation, adhesion, senescence, and apoptosis [ 8 , 9 ]. In addition, IGFBP7 is abundantly expressed in reproductive organs including blood vessels in the preovulatory follicular wall [ 22 ], granulosa cells of antral follicles [ 23 ], the CL [ 23 , 24 ], and the endometrium [ 25 , 26 ]. Several studies, including ours, have suggested that IGFBP7 functions as a physiological regulator of uterine receptivity [ 25 , 26 ] and follicular steroidogenesis [ 23 ].…”