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

Madeleine F Scriba12, Anne-Lyse Ducrest2, Isabelle Henry2, Alexei L Vyssotski3, Niels C Rattenborg1* and Alexandre Roulin2*

Author Affiliations

1 Avian Sleep Group, Max Planck Institute for Ornithology, Eberhard-Gwinner-str.11, Seewiesen 82319, Germany

2 Department of Ecology and Evolution, University of Lausanne, Lausanne 1015, Switzerland

3 Institute of Neuroinformatics, University of Zürich and ETH Zürich, Zürich 8057, Switzerland

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Frontiers in Zoology 2013, 10:42  doi:10.1186/1742-9994-10-42

Published: 26 July 2013

Abstract

Background

Intra-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).

Results

As 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.

Conclusions

We 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.

Keywords:
REM sleep; Melanocortin; Melanism; Pleiotropy; Ontogeny; Development; Avian