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

Abstract

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.

Age‐dependent timing and routes demonstrate developmental plasticity in a long‐distance migratory bird

“…photoperiodic control of pre‐migratory fattening, physiological control of fattening rates, absolute potential fuel loads, etc. ); (b) experimentally revealing the organismal limits of these component traits, that is, their full reaction norms; (c) employing transcriptomic and genomic approaches to understand the genetic basis that may underlie these component traits, to try to disentangle the extent to which plasticity is organismal or conditional (Horton et al., 2019 ); and (d) developing an ecological understanding of how trade‐offs among these component traits may limit the potential for plastic responses to changes within the environmental range covered by individual reaction norms. Studies of bird migration thus have the potential to illuminate the most fundamental questions about the generation of phenotypic variation and also help us understand the organismal limits to contemporary global change (Gienapp et al., 2014 ).…”

Endogenous Programs and Flexibility in Bird Migration

“…The avian circadian system consists of several pacemakers (Figure 4) that are interconnected, and are in turn sensitive to multiple environmental sensory inputs as well as to signaling from within the body (Kumar et al, 2006;Cassone, 2014;Helm et al, 2017). The particular responsiveness of Zugunruhe (see Adjusting the Drive to Migrate and Fueling in Response to Geomagnetic Cues) to food availability suggests links of the Zugunruhe oscillator to metabolic signals, and perhaps to brain circuits that are part of the award system (Bartell and Gwinner, 2005;Horton et al, 2019).…”

Dynamic molecular evolution of a supergene with suppressed recombination in white-throated sparrows

“…The second data set consisted of gene expression in female and nestlings of both sexes during the breeding season in same two brain regions (Hyp and AMV) (Grogan et al, unpublished data). The third data set consisted of gene expression in heart and liver tissue in white-striped males collected during migration, then housed in captivity under two lighting conditions (long days and short days) and sampled at two time points during the day (ZT6 and ZT18) ( 84 ). In statistical analyses, the females and nestlings were treated as separate “batches” of RNAseq such that there were four total batches.…”

“…The second data set consisted of gene expression in the same two brain regions (Hyp and AMV) in adult females collected during the breeding season as well as male and female nestlings (see ( 39 ) for details). The third data set consisted of gene expression in heart and liver tissue in white-striped males collected during migration, then housed in captivity under two lighting conditions (long days and short days) and sampled at two time points during the day (ZT6 and ZT18) ( 84 ). In statistical analyses, the females and nestlings of each sex were treated as separate “batches” of RNAseq such that there were five total batches: brain samples from adult males, adult females, nestling males, nestling females, and liver/heart samples from adult males.…”