Genomic and Peptidomic Characterization of the Developing Avian Brain

Chicken and Japanese quail are commonly used models in developmental and sex specific neuroendocrine research. There is relatively little known about the mechanisms behind their sex specific brain development, especially regarding the impact of the sex chromosomes (male: ZZ, female ZW) in relation to gonadal hormones. This thesis explores several aspects of these processes. Gene expression analysis with cDNA and Affymetrix arrays on brain tissue from both pre-gonadal embryos and embryos with differentiated gonads indicate a strong sex chromosomal presence in sexual dimorphic somatic tissue development in both chicken and Japanese quail. This sex chromosome pattern seems to remain in adult brain tissue. The data demonstrates that chicken males exhibit a significant level of Z-gene dosage compared to females in both somatic and germ line derived embryonic tissues. Several avian sex determination gene candidates (MHM non-coding RNA, DMRT1, HINTW, and HINTZ) were analyzed by real-time PCR. DMRT1 is dosage compensated in male brain tissue, in contrast to its reported gene dosage in male gonads. Early embryonic ethinylestradiol (EE2) exposure did not affect male or female neural gene expression patterns during later development. A peptidomics analysis on quail embryonic day 12 (ed12) and ed17 diencephalon by LC-MS identified over 60 endogenous peptides and analyzed the expression patterns for 38 of them with regard to age, sex and early EE2 exposure. There was a general upregulation between ed12 and ed17, but no clear sex effects were detected. Multivariate analysis indicates that EE2 exposed individuals differ from control individuals in a gender independent manner, and that Gonadotropin-inhibiting hormone related peptide 2 (GnIH-RP2) is a candidate for EE2 induced peptidomic alterations in male embryonic brain.