조피볼락, Sebastes sclegeli의 성분화 기간 중 cytochrome P450 aromatase 유전자의 발현
Expression of cytochrome P450 aromatase genes during sex differentiation in Korean rockfish, Sebastes schlegeli
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자웅이체형 어류의 성결정 및 성분화는 일반적으로 각 개체의 유전형을 따른다. 자연환경에서는 자신이 가진 유전정보의 조절에 따라 성분화 시기에 아로마테이즈 유전자의 발현이 증가하거나 감소하고 그 결과 스테로이드 호르몬들의 조성이 결정되어 각기 다른 방향으로 성분화하는 것으로 알려져 있다. 본 연구에서는 해산 태생어류인 조피볼락(Sebasts schlegeli)의 ovarian type aromatase (P450aromA)와 brain type aromatase (P450aromB)의 유전자를 부분적으로 클로닝하여, 이들의 염기서열을 밝혔으며, 각 유전자에 대한 primer를 제작한 후 성분화 기간 중 이 유전자들의 발현을 조사하였다. 조피볼락 아로마테이즈 유전자들은 조사를 시작한 출산 후 35일째에 여러 개체의 머리와 몸에서 각각 발현되었으나, 52일째에는 아로마테이즈 유전자들의 발현 개체수가 현저히 감소하였다. 그리고 출산 59일째에는 발현개체 수가 다시 증가하였다. P450aromA과 P450aromB의 발현 양상은 전반적으로 유사하였으나, 45일째에는 P450aromB의 발현 개체 수가 P450aromA 발현 개체 수 보다 훨씬 많았다. 조직학적 분석을 통해 제시된 이 종의 성분화 시기는 지금까지 출산 50-65일 전후로 알려져 왔으나, 본 연구에서 나타난 아로마테이즈 유전자들의 발현 결과를 볼 때, 이 종의 실질적인 성분화는 알려진 것보다 최소한 1-2주 정도 빨리 진행될 가능성이 있다. 본 연구의 결과는 또한 태생어류의 성분화도 난생어류의 성분화에서 보고된 것과 마찬가지로 아로마테이즈의 작용과 밀접하게 연관되어 있다는 사실을 시사한다.
Abstract
Sex determination and sex differentiation are influenced by genotype in many gonochoristic fish. Cytochrome P450 aromatase (CYP19) is the terminal enzyme in steridogenic pathway that converts androgens into estrogens. In this study, partial fragments of aromatase genes (ovarian aromatase, P450aromA and brain aromatase, P450aromB) were cloned and sequenced in Korean rockfish (Sebastes schlegeli), and gene specific primers were designed based on their sequences. Using these primers, aromatase gene expression during sex differentiation was investigated by RT-PCR. Expression of these aromatase genes were detected both in the head and body parts at 35 dab (days after birth). The number of fish that expressed the aromatase genes decreased at 52 dab, implying down-regulation of these genes. However, these genes were expressed at 59 dab in almost all fish studied here. The expression patterns of both genes are similar throughout the investigated period except for 45 dab where the expression of P450aromB was detected in more fish than that of P450aromA both in the head and body parts. Timing of sex differentiation in this species has been shown to be at around 50-65 dab by histological analysis. However, the results from this study suggest that sex differentiation of rockfish may take place 1-2 weeks earlier than the period proposed previously. The results also suggest that the mechanism of sex differentiation in viviparous fish may be similar to that in oviparous fish in terms of the importance of aromatase action during the critical period.
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