Submitted to: Domestic Animal Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 6, 2001
Publication Date: May 20, 2001
Citation: Kim, J.G., Vallet, J.L., Christenson, R.K. 2001. Characterization of uterine epidermal growth factor during early pregnancy in pigs. Domestic Animal Endocrinology. 20(4):253-265. Interpretive Summary: Uterine capacity is a component trait contributing to litter size in the pig. The epidermal growth factor (EGF) gene, on porcine chromosome 8, may influence uterine capacity because of its growth-promoting activities. However, the entire coding region of the porcine EGF precursor cDNA has not been cloned. Furthermore, relative expression of EGF mRNA has not been well lcharacterized during embryo elongation, implantation, and early developmen of the placenta (day 10 to 40). Therefore, an experiment was conducted to clone the full length cDNA for EGF precursor and to determine changes in expression in EGF mRNA during early pregnancy. The full length cDNA of EGF precursor (4932 base pair) was obtained and the predicted protein sequence of the EGF precursor contained 1214 amino acids. EGF mRNA expression was compared on day 10, 13, and 15 cyclic, and day 10, 13, 15, 20, 30, and 40 pregnant pigs. EGF mRNA expression decreased significantly from day 13 to 15 of the cycle and pregnancy, and from day 30 to 40 of pregnancy. These findings show that EGF mRNA expression is temporally regulated during the cycle and early pregnancy, and this pattern of gene expression may be important during early conceptus development. These results aid in the study of the role of precursor and mature form EGF in uterine capacity and litter size in the pig.
Technical Abstract: Genomic research has identified a quantitative trait locus for uterine capacity, a component trait contributing to litter size, on porcine chromosome 8. The epidermal growth factor (EGF) gene, on porcine chromosome 8, may influence uterine capacity because of its growth-promoting activities. Using reverse transcription-polymerase chain reaction and iterative screening of a porcine reproductive tissue cDNA library, 4932 bp cDNA sequence coding for porcine EGF precursor was obtained. The predicted protein sequence of the EGF precursor contained 1214 amino acids, similar to human EGF precursor (1207 amino acids, 81% identity). Curiously, the sequence of the mature peptide was less homologous between species than other regions of EGF precursor. The presence of conserved regions outside the mature peptide may suggest that these regions are functionally important. Expression of EGF mRNA in the endometrium of White crossbred gilts (n = 3 to 5 each) was determined by Northern blotting using 20 ug of total RNA from endometrium of D 10, 13, and 15 cyclic, and D 10, 13, 15, 20, 30, and 40 of pregnant gilts. A 3342 bp probe from EGF precursor was used. The bands corresponding to EGF mRNA were quantified by densitometry and results were analyzed by ANOVA. EGF mRNA expression decreased significantly from D 13 to 15 of the cycle and pregnancy (P = 0.04), and from D 30 to 40 of pregnancy (P = 0.01). These findings show that EGF mRNA expression is temporally regulated during the cycle and early pregnancy, and this pattern of gene expression may be important during early conceptus development.