Contribution of domestic animals to the identification of new genes involved in sex determination

Among farm animals, two species present an intersex condition at a relative ly high frequency: pig and goat. Both are known to contain XX sex-reversed individuals which are genetically female but with a true hermaphrodite or m ale phenotype. It has been clearly demonstrated that the SRY gene is not in volved in these phenotypes. Consequently, autosomal or X-linked mutations i n the sex-determining pathway may explain these sex-reversed phenotypes. A mutation referred to as "polled" has been characterized in goats by the sup pression of horn formation and abnormal sexual differentiation. The Polled Intersex Syndrome locus (PIS) was initially located in the distal region of goat chromosome 1. The homologous human region has been precisely identifi ed as an HSA 3q23 DNA segment containing the Blepharophimosis Ptosis Epican thus locus (BPES), a syndrome combining Premature Ovarian Failure (POF) and an excess of epidermis of the eyelids. In order to isolate genes involved in pig intersexuality, a similar genetic approach was attempted in pigs using genome scanning of resource families. Genetic analyses suggest that pig intersexuality is controlled multigenica lly. Parallel to this work, gonads of fetal intersex animals have been stud ied during development by light and electron microscopy. The development of testicular tissue and reduction of germ cell number by apoptosis, which si multaneously occurs as soon as 50 days post coitum, also suggests that seve ral separate genes could be involved in pig intersexuality. J. Exp. Zool. 2 90:700-708, 2001. (C) 2001 Wiley-Liss, Inc.