Exploring Sexual Differentiation in the Tammar Wallaby Using Transcriptomics

Sex determination and sexual differentiation are some of the most well studied topics in human development. Sex determination is the point where the undifferentiated gonad becomes committed to the ovarian or testicular pathway. This event can be triggered genetically or environmentally. Sexual differentiation occurs after sexual determination and involves the maturation of the gonad, which in turn, coordinates the corresponding physical and behavioral phenotypes. Disorders of sexual development (DSD) are among the most common congenital abnormalities seen in humans and are increasing at an alarming rate. Congenital DSDs can be caused by genetic, hormonal, and/or environmental stimuli. Increased exposure to environmental endocrine disrupters (EEDs) especially those that affect estrogen signaling have been shown to cause DSDs. In addition to the mouse, the tammar wallaby, Macropus eugenii, has become a novel model for studying gonadal differentiation in mammals. Unlike mice, sexual determination and differentiation occurs postpartum in the tammar. Furthermore, pouch young are easily accessible for surgical and hormonal manipulation. More is known about testicular differentiation than ovarian differentiation. Thus, there is a substantial need to create transcriptomes as a resource in discovering conserved and novel mechanisms in gonadal development. This thesis explores the creation and analyses of these transcriptomes using normal male and female developing gonads and estrogen induced ovarian development in male marsupial gonads. It will also show that the tammar wallaby is a viable model for studying gonadal differentiation and the effects of estrogen in sexual development in mammals