Developmentally regulated expression of c-Fos and c-Jun in the brainstem auditory nuclei of Gallus domesticus is modified by prenatal auditory enrichment.

Recognition of mother's voice by human neonates and behavioral responses of birds and animals to sounds experienced prenatally emphasize the role of sensory inputs in auditory system development. Spontaneous and experience driven neural activity influence the neural circuits' refinement in developing brain. However, cellular mechanisms endowing plasticity for such structural refinement during critical developmental periods are less understood. Sensory stimulation induces fluctuating expression of transcription factors (TFs) of Fos, Jun, and Krox families in the related brain nuclei to activate genes to synthesize proteins such as those needed for cytoskeletal structures, ion channels, and regeneration. To understand the cellular mechanism of response to prenatal auditory stimulation, we studied the expression of c-Fos and c-Jun in brainstem auditory nuclei, nucleus magnocellularis, and nucleus laminaris of the domestic chick. The chick brainstems, five each of E8 (embryonic day 8), E12, E16, E20, and posthatch day 1 were processed for immunohistochemistry as well as Western blotting and quantified using image analysis systems. In controls, c-Fos and c-Jun expression in both the nuclei was developmentally up-regulated. Reduced c-Fos expression and increase in c-Jun was temporarily observed between E12-16. In the stimulated groups, c-Fos expression was elevated while c-Jun showed a reduction matched to controls. This diametrically opposing pattern of c-Fos and c-Jun expression in response to stimulation is indicative of cell survival. Thus the expression of TFs in the auditory nuclei shows a relationship beyond a simple stimulation-activity-expression. While developmental signals control the expression of TFs, extra sensory stimulation modulates their expression to possibly support neuronal survival and enhance synthesis of other proteins.