Socially Responsive Yolk Steroids Correlate with Early Extraembryonic Gene Expression

Here, we identify socially sensitive yolk hormones and explore their relationship with transcript-wide gene expression patterns in extra-embryonic tissues during early embryonic development in male and female house sparrows (Passer domesticus). To enable the latter, we additionally characterized how yolk hormones change across development to identify the period during which maternally derived hormones are present. We exposed captive-breeding house sparrows to simulated territorial intrusions throughout the yolking period and collected eggs to measure >30 yolk hormones using LC-MS-MS. We additionally collected unmanipulated eggs from the aviary and the wild and incubated them to one of three timepoints: embryonic day 0 (ED0), ED3, or ED5. We characterized how yolk hormones changed across development and then explored relationships between transcript-wide gene expression levels in ED3 extra-embryonic tissues and levels of yolk hormones that are responsive to social stimuli. Overall design: Eggs were unmanipulated and incubated to embryonic day (ED) 3 or 5. RNA was collected from extraembryonic and brain tissues.