Length polymorphism of PCR-amplified genomic fragments of the Pregnancy-Associated Glycoprotein (PAG) gene family in the pig and some other domestic and wild mammals
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Porcine pregnancy-associated glycoprotein genes (pPAG) are known as a multigene family, in which five members have been cloned and sequences of their cDNAs identified. Porcine PAG1 and pPAG3 genes, belonging to the pPAG1-like subfamily, both encode enzymatically inactive precursors. In contrast, cDNAs of pPAG2, pPAG4 and pPAG6 represent the pPAG2-like gene subfamily, encoding enzymatically active precursors. The objective of this study was to investigate the polymorphism of both pPAG-like gene subfamilies in the pig in comparison to other domestic species, including cattle, sheep and goat (Artiodactyla), their wild relatives (red deer and wild pig) and horse (Perissodactyla). This is the first paper indicating the polymorphism of the pPAG gene family, examined by lengths of amplified genomic fragments (PCR). Obtained PCR products were analysed in relation to five characterised cDNAs of pPAGs (pPAG1-like and/or pPAG2-like subfamilies) and according to one recognised structural exon-intron organisation of the pPAG2 gene, among at least eight pPAG2-like genes expected in the porcine genome. The highest polymorphism frequency of both pPAG1- and pPAG2-like gene subfamilies was found in the second region, exons 5 and 6 (with intron E). The length of PCR-amplified genomic fragments was approximately: 1043, 700, 600 and 193 bp. A high polymorphism frequency was found in the 3?-terminal fragment, corresponding to exons 7-9 (with introns G and H), more frequent the pPAG2-like gene subfamily. The length of PCR-amplified genomic fragments was approximately: 733, 650 and 356 bp. In contrast, PAG polymorphism was not detected in another region, encompassing exons 2-4 (with introns B and C). The length of PCR-amplified genomic fragments was approximately 279 bp in all examined genomes. In conclusion, amplification of various regions of the PAG gene family presents a relatively inexpensive PCR method of animal pre-selection with different genotypes. Such a pre-selection of animals is helpful for further gene number inquiry of the PAG gene family in each animal, then in related generations. The obtained results provide a useful background for a genetic marker preparation (by Southern analysis of the PAG family) that will presumably enable an economical early selection of young animals for effective reproduction.
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B. Szafranska, Department of Animal Physiology, Faculty of Biology, University of Warmia and Mazury, 10-718 Olsztyn-Kortowo, Oczapowskiego 5, Poland, e-mail: firstname.lastname@example.org