PARENT SESSION
DEVELOPMENT OF THE EMBRYO
Harborside C
7:30 AM-10:00 AM

(153) IDENTIFICATION OF UNIQUE GENES EXPRESSED DURING SEX INVERSION OF NILE TILAPIA, Oreochromis niloticus, BY cDNA SUBTRACTIVE HYBRIDIZATION 1.

Contreras-Sanchez, Wilfrido¹, Fitzpatrick, Martin², Alonso, Marta³, Schreck, Carl⁴, Leong, Jo-Ann³, ¹ Laboratorio de Acuacultura, Villahermosa, MX² Department of Environmental Quality, Portland, OR³ Department of Microbiology, Corvallis, OR⁴ Department of Fisheries and Wildlife, Oregon State University, Corvallis, OR

ABSTRACT- The genetic control of sex differentiation in mammals has been linked to the expression of several specific genes, including SRY, the purported testis-determining factor; however in fish, these genes have either not been identified or are present in both sexes. Therefore, to identify the genes involved in sex differentiation in fishes, we have utilized induction of sex inversion in Nile tilapia (Oreochromis niloticus) to produce phenotypic males and combined this with subtraction hybridization techniques to investigate the mechanism of sex determination and gonadal differentiation. Fry were immersed for brief periods in the masculinizing synthetic steroid, trenbolone acetate, during early development; shortly thereafter, RNA from treated and untreated fish was isolated and used to identify the expression of unique mRNAs during the process of sex inversion through the use of suppression subtractive hybridization. mRNA collected 16 hrs after treatment suggests that short-term immersion of tilapia fry in trenbolone acetate induces the expression of unique genes. We have sequenced 165 clones from which 61 proteins have been identified. A significant number of these genes seem related to the anabolic effects of trenbolone acetate. We have also identified 12 genes related to reproductive tissues; seven of which have unique or enriched expression in the testes. Some of the genes and protein products that have been identified are linked to gonadal development and testicular protein synthesis in other species.

KEY WORDS: cDNA library, Masculinization, Nile tilapia, Trenbolone Acetate