Meeting Abstract
69.5 Thursday, Jan. 6 The neurogenetics of avian photoperiodism: a key role for gonadotropin releasing hormone 1 (GnRH1). STEVENSON, TJ*; BALL, GF; Johns Hopkins University tsteve13@jhu.edu
In recent years there has been an exponential increase in the ability to identify the sequence of genetic events that lead to a functional change in physiology and behavior. In many temperate zone avian species, the vernal increase in photoperiod is the initial predictive cue that triggers a cascade of genetic changes resulting in a dramatic shift in neuroendocrine state. The current challenge is identifying candidate genes that are critical for light detection and the subsequent change in gene expression across different hypothalamic regions. Japanese quail have been a valuable model species for elucidating the role of a number of genes that govern the photoinducible phase. However, little is known regarding the genetic sequence underlying the photoperiodic response in passeriformes. This presentation will cover two closely related topics: 1) the annual change in a specific gene, gonadotropin-releasing hormone 1 (GnRH1) that reliably predicts that annual change in passeriform reproductive physiology; and 2) current studies investigating candidate genes that are expressed across different photoperiodic states. The first part will illustrate that the photoperiodic variation in GnRH1 mRNA is anatomically localized in the preoptic area and that a decline in GnRH1 mRNA expression is associated with the onset of photorefractoriness and an increase in GnRH1 mRNA predicts the beginning of another reproductive period (i.e. the state of photosensitivity). The second part of the presentation will discuss recent findings from studies investigating the variation in the expression of a number of genes that are important for the transitions across the photoinduced reproductive cycle. Together these data identify a number of candidate genes that underly the avian photoperiodic response and will provide new avenues for research on the neuroendocrine control of seasonal reproduction.
