Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: April 4, 2003
Publication Date: June 1, 2003
Citation: KIM, J.G., VALLET, J.L., NONNEMAN, D.J., ROHRER, G.A., CHRISTENSON, R.K. MOLECULAR CHARACTERIZATION AND ENDOMETRIAL EXPRESSION OF PORCINE SMAD1. JOURNAL OF ANIMAL SCIENCE SUPPLEMENT. 2003. v. 81(Suppl. 1). p. 243. Abstract No. T27. Technical Abstract: Uterine capacity contributes to litter size in swine. Previous gene mapping analyses revealed a quantitative trait locus (QTL) for uterine capacity on chromosome 8. Comparison of porcine and human genetic maps suggests that the Smad1 gene is located near this region. Smad1 mediates signal transduction from TGF-beta family ligands, including TGF-beta and bone morphogenetic proteins. In addition, Smad1 mutation in mice causes defects in allantois formation. To further explore Smad1 as a candidate gene for the uterine capacity QTL, we 1) cloned and sequenced the full coding region for Smad1, 2) examined endometrial expression of Smad1 during the estrous cycle and early pregnancy, and 3) mapped the Smad1 gene. By iterative screening of a porcine expressed sequence tag library, we obtained 2161 and 2077 bp cDNA clones containing the full coding region of Smad1. The two clones differed in their 5' untranslated regions while their coding regions were identical, suggesting differential splicing. The inferred amino acid sequence of porcine Smad1 was 99.8% identical to human Smad1. Endometrial expression of Smad1 mRNA in White composite gilts (n = 3 to 4) was determined by Northern blotting using total RNA from d 10, 13 and 15 cyclic and from d 10, 13, 15, 20, 30 and 40 pregnant gilts, followed by densitometry. Endometrial expression of Smad1 mRNA was greater (P < 0.05) on d 10 (47.6 +/- 3.8 arbitrary units) of pregnancy than d 10 (36.2 +/- 3.8) of the estrous cycle. In both pregnant and cyclic gilts, endometrial expression of Smad1 mRNA was lower (P = 0.03) on d 15 (33.8 +/- 3.8, 40.2 +/- 3.8) than d 13 (44.0 +/- 3.8, 48.4 +/- 4.4), respectively. The Smad1 gene was mapped to chromosome 8, position 78 cM, near the peak of the uterine capacity QTL (71 cM). Elevated endometrial expression of Smad1 mRNA on d 10 of pregnancy suggests a role for Smad1 in signal transduction in endometrium during this period and the location of the Smad1 gene in the porcine genome is consistent with it being a candidate gene for the uterine capacity QTL.