Molecular cloning and single nucleotide polymorphism analysis of IGF2a genes in the common carp (Cyprinus carpio)

We studied whether two IGF2 transcripts in common carp are similar to those found in zebrafish. The full-length IGF2a cDNA contains a 5'-terminal untranslated region (UTR) of 105 bp, a 3'-terminal UTR of 1358 bp and an open reading frame of 612 bp, which encodes a 206-amino acid protein. A 6614-bp full-length IGF2a DNA molecule, including the 5'-flanking region, was isolated. Genomic DNA structure analysis revealed that the IGF2a gene contains four exons and three introns. Bioinformatics analysis indicated that the proteins encoded by IGF2a genes in common carp have one signal peptide and one apparent transmembrane region. Bootstrapping was performed 1000 times to obtain support values for each branch. The common carp IGF2a were clustered in one group, while the outgroup (common carp IGF1) clustered in another group. We identified two new single nucleotide polymorphisms in intron 2 of the gene. One polymorphism, A/N, can be found only in the Huanghe carp. The other polymorphism, C/N, can be found in both male Huanghe carp × female Heilongjiang carp and male Huanghe carp × female Jian carp. The second polymorphism, C/N, is primarily transferred from the male and may be related to heterosis.