Transcriptome Analyses of Heart and Liver Reveal Novel Pathways for Regulating Songbird Migration

Many birds undertake long biannual voyages during the night. During these times of the year birds drastically reduce their amount of sleep, yet curiously perform as well on tests of physical and cognitive performance than during non-migrating times of the year. This inherent physiological protection disappears when birds are forced to stay awake at other times of the year; thus these protective changes are only associated with the nocturnal migratory state. The goal of the current study was to identify the physiological mechanisms that confer protection against the consequences of sleep loss while simultaneously allowing for the increased physical performance required for migration. We performed RNA-seq analyses of heart and liver collected from birds at different times of day under different migratory states and analyzed these data using differential expression, pathway analysis and WGCNA. We identified changes in gene expression networks implicating multiple systems and pathways. These pathways regulate many aspects of metabolism, immune function, wound repair, and protection of multiple organ systems. Consequently, the circannual program controlling the appearance of the migratory phenotype involves the complex regulation of diverse gene networks associated with the physical demands of migration.