Molecular characterization, polymorphism and association of porcine IBP4 gene

The complete coding sequence of the porcine IBP4 gene was isolated using RT-PCR. Sequence analysis showed that the porcine IBP4 gene encodes a protein of 259 amino acids which shares high homology with the insulin-like growth factor binding protein 4 (IBP4) of eight species: cattle (97 %), goat (97 %), chimpanzee (97 %), human (96 %), giant panda (96 %), sheep (95 %), Sumatran orangutan (95 %) and rabbit (93 %). This gene is structured in four exons and three introns as revealed by computer- assisted analysis. Phylogenetic analysis revealed that the porcine IBP4 gene has a close genetic relationship with the IBP4 gene of cattle. Polymorphism analysis indicated that there was an A/G substitution in the position of 134 bp of exon 2 and this mutation did not alter the encoded amino acids of the porcine IBP4 gene. PCR-Hha I-RFLP revealed that eight pig breeds displayed obvious genotype and allele frequency differences at this polymorphic locus. Association of this SNP with litter size traits was assessed in Large White (N = 100) and Landrace (N = 100) populations, and the results demonstrated that this polymorphic locus was significantly associated with the litter size of the first parity in Large White sows and Landrace sows (P <0.05). These data serve as a foundation for further insight into this novel porcine gene.