The Effect Of IGF-1Gene On The Dwarf Trait In Porcine

IGF-1, mediating the growth-promoting activity of growth hormone, is theimportant factor of growth and metabolism in animal body, IGF-1plays an importantrole in the normal growth of cells, bone remodeling, embryonic development, nervegrowth and so on. Tibetan Mini-pig is one of Chinese miniature pig breeds thattraditionally recognized to be the relatively slow growth and small size of mutualinvestment. Tibetan Mini-pig is an ideal experimental animal as the model of dwarfanimals in the biology and the comparative medicine, because of the similiarities ofthe physiological characteristics and metabolism with those of human.In this study, we used molecular biology techniques to study the effects ofgenetic variation of IGF-1gene on the dwarf trait in Tibetan Mini-pig. IGF-1wasassumed as candidate genes in four different pig breeds: Tibetan Mini-pig, BamaMiniature Pig, Northeastern Wild Boar and Junmu-1Pig. And the results showedthat：1. In the promoter region of IGF-1gene, compared with the others, BamaMiniature Pig missed a possible CdxA binding site and a possible NKx-2binding site.Moreover, compared Junmu-1Pig with Tibetan Mini-pig and Northeastern Wild Boar,we found a possible MZF1binding site in Junmu-1Pig. The evolutionary tree amongfour species, constructed by the neighbor-joining method, showed that TibetanMini-pig had a recently genetic relationship with Bama Miniature Pig; and a closelygenetic relationship with Northeastern Wild Boar. And the genetic relationshipbetween Junmu-1Pig and the others was the fastest. The structures of the promoterregion of IGF-1gene have difference in different body length pig.2. The genetic diversity of IGF-1gene was analyzed by Allele-specific PCR(AS-PCR) in four different pig breeds. We have predicted only one SNP site, andanalyzed the PCR products by electrophoresis and specific amplification, whichindicated that only one was predicted and the allele presented in A3320G. The resultsshowed that three genotypes (AA, AG and GG) distributed averagely in Northeastern Wild Boar and Junmu-1Pig although they were detected in all breeds. Thedistribution of the G3320A alleles in all breeds was significantly different (P<0.05),and G-allele carriers had a greater reduction than A-allele carriers exclusively inTibetan Mini-pig.3. The expression levels of IGF-1in different tissues were tested with Real-TimePCR and immunohistochemistry (IHC). The results of Real-time PCR indicated thatIGF-1mRNA expression levels of liver tissues in neonatal had significant difference(P<0.05) between Tibetan Mini-pig and Junmu-1Pig. In addition, the results ofimmunohistochemist showed that IGF-1concentration of bones in weaned hadsignificant difference (P<0.05) between Tibetan Mini-pig and Junmu-1Pig.This research demonstrated that the IGF-1gene expression regulatory mode ofTibetan Mini-pig had difference compared with Junmu-1Pig, and the IGF-1geneexpression also had differences in liver and bone at different developmental stagescompared with Junmu-1Pig, thereby the dwarf trait in Tibetan Mini-pig maybe due tothe genetic variation and differential expression.