Establishment of a reptile model animal and the effect of environmental temperature on the reproduction.

有鳞目动物为了适应其生活环境，表现出多种生殖现象，如卵生和胎生、基因型性别决定和温度依赖性性别决定。这些发现为我们探讨脊椎动物生殖现象的进化提供了一把很好的钥匙。然而，这些复杂性状的分子机制仍然没有得到普遍的理解，因为缺乏在这个动物群体中的模式物种。豹纹壁虎，Eublepharis macularius，很容易驯服，也很容易在实验室里繁殖，不像其他有鳞动物。在这种动物中，胚胎发育期间的孵化温度决定了它们的性腺性别。本研究以金钱壁虎为研究对象，克隆了P450 arom、P450 SCC、雌激素受体和SF-1基因的cDNA，研究环境因素对金钱壁虎性别分化相关基因表达的影响。并定量分析了孵育温度对这些基因mRNA表达的影响。P450 arom和SF-1蛋白在孵化后的表达量存在性别差异。这些类固醇生成酶的mRNA表达不仅在大脑中，但也在性腺前的温度敏感期的性别决定。四种性类固醇激素受体的mRNA也在大脑和性腺中检测到。这些结果有力地表明，在发育中的豹壁虎大脑中存在一个不依赖于性腺的性类固醇激素信号系统。

Squamata species shows various reproductive phenomena, such as oviparity and viviparity, genotypic sex determination and temperature-dependent sex determination to adapt the environments of their habits. These diversities give us a good key to discuss the evolution of reproductive phenomenon in vertebrate. However, the molecular mechanisms underlying such complex traits are still not generally understood because of lacking the model species in this animal group. The leopard gecko, Eublepharis macularius, is easily tamed, and is easy to breed in the laboratory, unlikely other squamata animals. In this animal, the incubation temperature during embryonic development determines their gonadal sex. From such characters, the leopard gecko was chosen in this study.To investigate on the effect of environmental factor on the expression of sex-differentiation related gene, we had cloned the cDNAs for P450scc, P450arom, estrogen receptors, and SF-1. And the effect of incubation temperature on the mRNA expression of these genes was examined quantitatively. The sex differences of the expression levels of P450arom and SF-1 were detected after hatching. The mRNA expression of these steroidogenic enzymes was detected not only in the brain but also in the gonad prior to the temperature-sensitive period of sex determination. The mRNAs of the four sex steroid hormone receptors were also detected in the brain and gonads at all stages examined. These results strongly suggest the existence of a gonad-independent sex steroid hormone signaling system in the developing leopard gecko brain.