The Effect of a Mutation in the Thyroid Stimulating Hormone Receptor (TSHR) on Development, Behaviour and TH Levels in Domesticated Chickens

The thyroid stimulating hormone receptor (TSHR) has been suggested to be a “domestication locus” in the chicken, due to a strong selective sweep over the gene found in domesticated chickens, but not in their wild ancestor the Red Junglefowl (RJF). We investigated the effect of the mutation on development (incubation time), behaviour and thyroid hormone levels in intercross chickens homozygous for the mutation (d/d), wild type homozygotes (w/w) or heterozygotes (d/w). This allowed an assessment of the effect of genotype at this locus against a random mix of RJF and WL genotypes throughout the rest of the genome. The (d/d) genotype showed a longer incubation time, less fearful behaviours, lower number of aggressive behaviours and decreased levels of the thyroid hormone T4, in comparison to the (w/w) genotype. The difference between TSHR genotypes (d/d vs. w/w) in these respects mirrors the differences in development and behaviour between pure domesticated White Leghorns and pure RJF chickens. Our study indicates that the TSHR mutation affects typical domestication traits and may therefore have been important during the evolution of the domestic chicken. At the time for thesis presentation publication was in status: ManuscriptFunding agencies|Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning, FORMAS (Formel Excel) [221-2010-35]; Swedish Research Council, VR [621-2011-4731]; European Research Council (ERC grant GENEWELL) [322206]