Identification of estrogen receptor α gene polymorphisms by SSCP and its effect on reproductive traits in Japanese flounder (Paralichthys olivaceus)

Estrogen receptor (ERα) modifies the expression of genes involved in cell growth, proliferation and differentiation through binding to estrogen response elements (EREs) located in a number of gene promoters, so the ERα gene is considered as an important factor affecting reproductive endocrinology in Japanese flounder (Paralichthys olivaceus). In this study, twelve single nucleotide polymorphisms (SNPs) within eight CDS exons and 1 kb of 3′-UTR of the ERα gene were tested to association with four reproductive traits in a population of 119 Japanese flounder individuals with polymerase chain reaction-single stranded conformational polymorphism (PCR-SSCP). The association analysis of SNPs within Japanese flounder ERα gene with the reproductive traits was carried out using General Linear Model (GLM) estimation. Results indicated that two SNPs in the exon4 of ERα gene, P1 (A803G and C864T), were significantly associated with hepatosomatic index (HSI) (P < 0.05) in female Japanese flounder. Other ten SNPs in 3′-UTR associated to serum 17β-estradiol (E2) and HSI showed that P2 (A1982T) was significantly associated with E2 (P < 0.01) and P3 (A2149G, 2181TTACAAG2182 insertion or deletion, T2324G, A2359G and G2391A) was significantly associated with HSI (P < 0.05) in female Japanese flounder. However, P2 (A1982T) and P4 (G2256T, T2294C, T2309G and A2333T) had significant effects on E2 (P < 0.05 and P < 0.01, respectively) in male Japanese flounder. In addition, there were significant associations between diplotype D1 based on fourteen SNPs and reproductive traits. The genetic effects for HSI (female) or E2 (male) of diplotype D1 were significantly higher than those of other eight diplotypes (P < 0.05), respectively. Our findings implied that P1 of ERα gene affecting the reproductive traits could be a potential QTN (quantitative trait nucleotide) which would be useful genetic marker in the selection of some reproductive traits for its in Japanese flounder.