PARENT SESSION
Sex Determination

DAX-1 TRANSGENE EXPRESSION IN ADULT AND EMBRYONIC GONADS.

Behdjani, Ramin¹, Pilon, Nicolas¹, Daneau, Isabelle¹, Lussier, Jacques¹, Silversides, David¹, ¹

ABSTRACT- DAX-1 is an unusual member of nuclear hormone receptor superfamily, which plays a critical role during gonadal and adrenal differentiation. To study the regulation of DAX-1 gene expression, a transgenic mouse model was generated using a reporter vector consisting of a 4 kb fragment of porcine DAX-1 5' flanking DNA in front of a yellow fluorescent protein reporter gene sequence (pDAX.EYFP). Transgenic embryos were recovered and genital-ridges were dissected and studied for transgene expression by fluorescence microscopy and immunohistochemistry using a commercial antibody generated against the GFP family of proteins and conjugated with alkaline phosphatase. While strong expression of fluorescence was detected in testis between 11.5-d.p.c and 19.5-d.p.c., no ovarian expression was observed during this period. Ovaries and testes of mice transgenic for pDAX.EYFP were recovered at different times postnatally and studied for transgene expression. Postnatally, expression was detected in a sub-population of seminiferous tubules by 3 weeks of the age, and in virtually all tubules in the adult where it was restricted to the meiotic stages of germ cells. In ovaries, strong expression was readily detected in oocytes starting from postnatal day 9 and appeared consistent with all stages of oocyte development. Within the pre-implantation embryo, when transgene came from maternal side, fluorescence was detected before cleavage and continued during morula stage, but declined in intensity and was hardly detectable by the blastula stage. Our transgenic model suggests an important role of the DAX-1 gene in testis development and spermatogenesis as well as in the regulation of oogenesis.

KEY WORDS: DAX-1, sex determination, transgenic mouse, promoter