Examining the role of external auditory stimuli on molecular mechanisms and the regulation of gene expression in the embryonic zebra finch

The ability to adapt to changing environments is crucial for all species. Growing evidence suggests that a wide variety of vertebrate species can influence the life course of their offspring in early development, including in the embryonic stages. One way in which this can occur is through sound. Human foetuses in the third trimester show increased cortical brain activity in response to sound. Avian species such as chickens and ducks also display evidence of hearing capacities in the embryonic stages and can respond verbally from within the egg. Recently, research in zebra finches has provided striking evidence that hearing different sounds during late embryonic development can confer environmental adaptations and change life course trajectory. At high ambient temperatures, adult nesting zebra finches emit an “heat call” and evidence shows that developing embryos exposed to this call are better adapted to hot temperatures. Hearing capacities of embryonic zebra finches have however never been demonstrated. I used molecular methods to probe the acute auditory response in embryonic zebra finches. I assessed whether acute sound playback affects expression of known sound responsive immediate early genes (IEGs) and investigated whether there are measurable genomic changes associated with specific sound conditions. I provide evidence that IEGs known to be sound responsive in adult zebra finches are not necessarily differentially regulated in response to sound in the embryonic zebra finch. I show that there is a measurable genomic response to acute sound playback and identify novel targets and gene sets that show subtle expression differences in response to sound. I also show that ribosomal genes are sound responsive and are differentially expressed depending on the type of call exposure. Overall, this supports the hypothesis that late-stage embryonic zebra finches possess hearing capacities and that different sound exposures produce different molecular responses in the developing brain. It supports the notion that zebra finch calls can be heard in the egg and that this could contribute to developmental reprogramming