Molecular characterization and expression of the GDF9 gene in New Zealand white rabbits

Growth differentiation factor 9 (GDF9) has been shown to be involved in regulating follicular development and reproduction in many mammalian species. However, related information about the effect of the GDF9 gene on reproductive traits of New Zealand white rabbits was rarely reported. In this study, rabbits were distributed into two groups (poor and prolific offspring productions) and cloning and quantitative real-time PCR (qPCR) were employed to characterize the rabbit GDF9 gene. By cloning, 2515-bp genomic DNA and 1359-bp cDNA sequences were obtained. Comparing the two cDNA sequences, three potential mutation sites (C.539C>T,C.562G>C and C.718C>G) in exon 2 of the GDF9 gene were found, and the corresponding amino acids changed (P.183T>M, P.188E>Q and P.240L>V). The qPCR results revealed that GDF9 was not tissue-specific, but rather expressed in all collected tissues. The expression level of the GDF9 gene was highest in the ovary, and was significantly increased (P< 0.05) compared with the other tissues. The liver had the second highest expression, and the heart and spleen had the least expression in New Zealand white rabbits. In the prolific group, the expression quantity of the GDF9 gene significantly increased (P < 0.05) in the heart, spleen, ovary, liver and uterus (P < 0.01) than the other groups. The amino acid sequence identities of human, sheep, goat, mouse, cattle, pig, cat, donkey, Nancy Ma's night monkey and olive baboon were 72, 68, 69, 66, 69, 71, 67, 73, 75 and 73%, respectively. Bioinformatics analysis was executed, and a random coil was determined to be the primary secondary structure.