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

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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.