Linking melanism to brain development: expression of a melanism-related gene in barn owl feather follicles covaries with sleep ontogeny

Abstract

BackgroundIntra-specific variation in melanocyte pigmentation, common in the animal kingdom, has caught the eye of naturalists and biologists for centuries. In vertebrates, dark, eumelanin pigmentation is often genetically determined and associated with various behavioral and physiological traits, suggesting that the genes involved in melanism have far reaching pleiotropic effects. The mechanisms linking these traits remain poorly understood, and the potential involvement of developmental processes occurring in the brain early in life has not been investigated. We examined the ontogeny of rapid eye movement (REM) sleep, a state involved in brain development, in a wild population of barn owls (Tyto alba) exhibiting inter-individual variation in melanism and covarying traits. In addition to sleep, we measured melanistic feather spots and the expression of a gene in the feather follicles implicated in melanism (PCSK2).ResultsAs in mammals, REM sleep declined with age across a period of brain development in owlets. In addition, inter-individual variation in REM sleep around this developmental trajectory was predicted by variation in PCSK2 expression in the feather follicles, with individuals expressing higher levels exhibiting a more precocial pattern characterized by less REM sleep. Finally, PCSK2 expression was positively correlated with feather spotting.ConclusionsWe demonstrate that the pace of brain development, as reflected in age-related changes in REM sleep, covaries with the peripheral activation of the melanocortin system. Given its role in brain development, variation in nestling REM sleep may lead to variation in adult brain organization, and thereby contribute to the behavioral and physiological differences observed between adults expressing different degrees of melanism.

Sleep-Related Electrophysiology and Behavior of Tinamous (<b><i>Eudromia elegans</i></b>): Tinamous Do Not Sleep Like Ostriches

“…However, for unexplained (probably technical) reasons this pattern was different in the hyperpallium for bird 1. Aside from this channel, the power spectra were similar to those described in other birds [Martinez-Gonzalez et al, 2008;Scriba et al, 2013].…”

“…In contrast, REM sleep is associated with an activated low-amplitude, high-frequency EEG pattern, as well as rapid eye movements, myoclonic twitching, and postural changes reflecting a relaxed skeletal muscle tone [Dewasmes et al, 1985]. In mammals and birds, the amount of REM sleep is highest in the young and it decreases over early ontogeny Jouvet-Mounier et al, 1970;Scriba et al, 2013]. SWS and REM sleep are both regulated in a similar manner in mammals and birds.…”

“…This plug was connected to a logger (Neurologger 2A; www.vyssotski. ch/neurologger2) that has been used extensively to record the EEG in birds [Vyssotski et al, 2009;Lesku et al, 2012;Scriba et al, 2013;Rattenborg et al, 2016]. The Neurologger also recorded 3-dimensional acceleration using an accelerometer located on the top of the circuit board.…”

Sleep and vigilance linked to melanism in wild barn owls

“…In a linear mixed model, PC1, which mainly captured time spent in the three states, as well as the number of non‐REM and REM sleep bouts (Table ), was not associated with parental plumage traits (Table ), but with nestling age as already shown in Scriba et al . ().…”

No association between the melanocortin-1 receptor (MC1R) and black belly stripe size variation in the Great TitParus major

“…Future studies should focus on additional melanogenesis genes, including MITF, ASIP, TYR and TYRP1, as earlier found in other species (Chang et al 2006, Minvielle et al 2010, Lehtonen et al 2011. Furthermore, other mechanisms of gene expression alterations such as mRNA expression and/or epigenetic alteration in the MC1R gene promoter should be considered (Fontanesi et al 2010, Emaresi et al 2013, Scriba et al 2013. Finally, we suggest that the architecture of phenotypic variation for this kind of small-scale variation such as black belly colouration may have a regulatory background rather than genetic polymorphism in the coding regions.…”