Sexual differentiation is the process by which hormones act to organize the developing body, including the brain, into male or female patterns. This process is proposed to occur by the action of steroid hormones, acting via receptors (such as the estrogen receptor), secreted by the gonads early in development. This research uses the Australian zebra finch (ZF; Taeniopygia guttata) to explore how hormones, such as estrogen, initiate different patterns of development in male and female brains. Songbirds, such as the ZF, have highly sexually dimorphic brains and behaviors. Males sing a courtship song females cannot sing and the brain regions controlling song are larger in the male brain. Recent research suggests that co-activator proteins are one possible mechanism through which steroids initiate differences in the brain. Co-activators greatly enhance the function of steroid receptors. The current project will use various techniques to examine if the amount and location of four estrogen receptor co-activator proteins are present at different levels in male and female ZF brain. Understanding the processes by which co-activator proteins influence steroid receptor function will add an important element to this field. This research will clarify how neuronal sex differences develop in all vertebrates and will provide a foundation for interpreting neuronal and behavioral sex differences across development. In addition, this work will promote the training of undergraduate and graduate students through the participation of students, in particular underrepresented groups, in this research. The training of students will enhance the infrastructure for education and research at GSU. Another important goal of this project is to increase the science knowledge of K-12 teachers and thus enhance the science learning and achievement of their students. This will be achieved by conducting a series of scientifically intensive hands-on teacher workshops. The research proposed in this application will serve as the basis for presenting material on animal behavior, neurobiology, and molecular biology with all information presented to the teachers based on the National Science Standards.
Sexual differentiation is the process by which hormones act to organize the developing body, including the brain, into male or female patterns. The process begins by establishing differences in the undifferentiated zygote and continues through development into adulthood. The resulting sex or gender differences can be examined at many levels including: genetic, chromosomal, gonadal, hormonal, anatomical, physiological, and behavioral. This process in vertebrate brain and behavior is hypothesized to be under the control of steroid hormones (testosterone and estradiol), secreted from the gonads (testes and ovaries) acting via their respective receptors on the nervous system during a critical window of time during development. In addition to the powerful effects exerted by steroid hormones, coactivator proteins also this process and play an integral role in regulating male and female specific behaviors. Coactivators act as molecular amplifiers (like the volume control on a stereo) and greatly enhance the function of steroids and their receptors (such as estrogen or androgen receptors). Currently there is little known about the role of these proteins on nervous system development. Songbirds, such as the Australian zebra finch (Taeniopygia guttata) are an excellent model system to use to examine the role of hormones and coactivators on brain development because this species has highly sexually dimorphic brains and behaviors. Males sing a courtship females cannot sing and the brain regions controlling song learning and production are much larger in males than females. These differences appear early in development and are fully formed by 30 days after hatching. In addition, the presence of male song provides a strong behavioral correlate that is directly connected with the sex differences in the brain. This research tested the hypothesis that the sex differences observed in the songbird brain are the direct result of coactivators proteins enhancing sex steroid receptor sensitivity. This research provided valuable data on the development of male and female differences in in the brain, and will contribute to the growing body of knowledge on neuronal and behavioral differences across development. Vertebrate steroid hormones are highly conserved evolutionarily and this work can be applied across the different vertebrate classes. Through this award we demonstrated that three coactivators are expressed in a sexually dimorphic manner in the zebra finch brain across development and that these proteins are located in the regions of the brain that control the learning and production of song. We also demonstrated that altering the amount of coactivator available in cell alters sexually dimorphic neuronal survival with fewer male neurons surviving after treatment than neurons from a female zebra finch brain. Finally, we demonstrated that reducing the amount of protein for one coactivator in the brain is enough to alter anatomy of two main song control structures but song learning and production were not significantly altered when male song was analyzed against tutor song. An additional and important goal of this project was to increase the science background knowledge of K-12 science teachers and thus enhance the science learning and achievement of their students. We achieved this goal by conducting five scientifically intensive hands-on week-long workshops for 3rd grade through high school-level science teachers. The workshops, titled "Why They Do What They Do at the Zoo" were held on-site at Zoo Atlanta during one week every summer from 2007-2011. The teachers learned neuroanatomy, endocrinology, animal behavior and science ethics, and toured behind the scenes at the zoo applying their knowledge to zoo animals. All information provided to the teachers was based on the National and Georgia Science Standards. Each teacher developed a lesson plan during the workshop and presented a draft to the entire group on the last day of the week-long session, This was followed by two follow up meetings, on Saturdays the following Fall and Spring semesters, during which teachers presented their final lessons plans back to the entire cohort for evaluation. This extended contact model for teacher profession development was successful for teachers and their students. The PI visited classrooms when lessons using the workshop materials were being taught and acted as a science advisor for all teacher participants.
