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The strong selective sweep candidate gene ADRA2C does not explain domestication related changes in the stress response of chickens.

Elfwing M, Fallahshahroudi A, Lindgren I, Jensen P, Altimiras J - PLoS ONE (2014)

Bottom Line: In hypothalamus and amygdala, regions associated with the stress response, and in striatum, receptor binding pIC50 values ranged between 8.1-8.4, and the level was not influenced by the genotyped allele.We did not find compelling genotype effects in open field, tonic immobility, aerial predator, associative learning or fecundity.Therefore we conclude that ADRA2C is probably not involved in the domestication of the stress response in chicken, and the strong selective sweep is probably caused by selection of some unknown genetic element in the vicinity of the gene.

View Article: PubMed Central - PubMed

Affiliation: AVIAN Behavioural Genomics and Physiology Group, Division of Biology, IFM Biology, Linköping University, Linköping, Sweden.

ABSTRACT
Analysis of selective sweeps to pinpoint causative genomic regions involved in chicken domestication has revealed a strong selective sweep on chromosome 4 in layer chickens. The autoregulatory α-adrenergic receptor 2C (ADRA2C) gene is the closest to the selective sweep and was proposed as an important gene in the domestication of layer chickens. The ADRA2C promoter region was also hypermethylated in comparison to the non-selected ancestor of all domesticated chicken breeds, the Red Junglefowl, further supporting its relevance. In mice the receptor is involved in the fight-or-flight response as it modulates epinephrine release from the adrenals. To investigate the involvement of ADRA2C in chicken domestication, we measured gene expression in the adrenals and radiolabeled receptor ligand in three brain regions comparing the domestic White Leghorn strain with the wild ancestor Red Junglefowl. In adrenals ADRA2C was twofold greater expressed than the related receptor gene ADRA2A, indicating that ADRA2C is the predominant modulator of epinephrine release but no strain differences were measured. In hypothalamus and amygdala, regions associated with the stress response, and in striatum, receptor binding pIC50 values ranged between 8.1-8.4, and the level was not influenced by the genotyped allele. Because chicken strains differ in morphology, physiology and behavior, differences attributed to a single gene may be lost in the noise caused by the heterogeneous genetic background. Therefore an F10 advanced intercross strain between White Leghorn and Red Junglefowl was used to investigate effects of ADRA2C alleles on fear related behaviors and fecundity. We did not find compelling genotype effects in open field, tonic immobility, aerial predator, associative learning or fecundity. Therefore we conclude that ADRA2C is probably not involved in the domestication of the stress response in chicken, and the strong selective sweep is probably caused by selection of some unknown genetic element in the vicinity of the gene.

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Behavioural variables from Tonic Immobility (TI) and Aerial Predator tests.A) TI induction attempts and B) TI duration (s). C) and D) Relaxed behavior pre and post exposure to the aerial predator in males (C) and in females (D). Data shown as mean and standard deviation. Star indicates a significant difference between genotypes (p<0.05).
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pone-0103218-g004: Behavioural variables from Tonic Immobility (TI) and Aerial Predator tests.A) TI induction attempts and B) TI duration (s). C) and D) Relaxed behavior pre and post exposure to the aerial predator in males (C) and in females (D). Data shown as mean and standard deviation. Star indicates a significant difference between genotypes (p<0.05).

Mentions: The number of attempts to initiate tonic immobility (1.9±1 attempts on average shown in Figure 4A) and duration (144±146 s) did not differ between genotypes or between sexes (Figure 4B).


The strong selective sweep candidate gene ADRA2C does not explain domestication related changes in the stress response of chickens.

Elfwing M, Fallahshahroudi A, Lindgren I, Jensen P, Altimiras J - PLoS ONE (2014)

Behavioural variables from Tonic Immobility (TI) and Aerial Predator tests.A) TI induction attempts and B) TI duration (s). C) and D) Relaxed behavior pre and post exposure to the aerial predator in males (C) and in females (D). Data shown as mean and standard deviation. Star indicates a significant difference between genotypes (p<0.05).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4128585&req=5

pone-0103218-g004: Behavioural variables from Tonic Immobility (TI) and Aerial Predator tests.A) TI induction attempts and B) TI duration (s). C) and D) Relaxed behavior pre and post exposure to the aerial predator in males (C) and in females (D). Data shown as mean and standard deviation. Star indicates a significant difference between genotypes (p<0.05).
Mentions: The number of attempts to initiate tonic immobility (1.9±1 attempts on average shown in Figure 4A) and duration (144±146 s) did not differ between genotypes or between sexes (Figure 4B).

Bottom Line: In hypothalamus and amygdala, regions associated with the stress response, and in striatum, receptor binding pIC50 values ranged between 8.1-8.4, and the level was not influenced by the genotyped allele.We did not find compelling genotype effects in open field, tonic immobility, aerial predator, associative learning or fecundity.Therefore we conclude that ADRA2C is probably not involved in the domestication of the stress response in chicken, and the strong selective sweep is probably caused by selection of some unknown genetic element in the vicinity of the gene.

View Article: PubMed Central - PubMed

Affiliation: AVIAN Behavioural Genomics and Physiology Group, Division of Biology, IFM Biology, Linköping University, Linköping, Sweden.

ABSTRACT
Analysis of selective sweeps to pinpoint causative genomic regions involved in chicken domestication has revealed a strong selective sweep on chromosome 4 in layer chickens. The autoregulatory α-adrenergic receptor 2C (ADRA2C) gene is the closest to the selective sweep and was proposed as an important gene in the domestication of layer chickens. The ADRA2C promoter region was also hypermethylated in comparison to the non-selected ancestor of all domesticated chicken breeds, the Red Junglefowl, further supporting its relevance. In mice the receptor is involved in the fight-or-flight response as it modulates epinephrine release from the adrenals. To investigate the involvement of ADRA2C in chicken domestication, we measured gene expression in the adrenals and radiolabeled receptor ligand in three brain regions comparing the domestic White Leghorn strain with the wild ancestor Red Junglefowl. In adrenals ADRA2C was twofold greater expressed than the related receptor gene ADRA2A, indicating that ADRA2C is the predominant modulator of epinephrine release but no strain differences were measured. In hypothalamus and amygdala, regions associated with the stress response, and in striatum, receptor binding pIC50 values ranged between 8.1-8.4, and the level was not influenced by the genotyped allele. Because chicken strains differ in morphology, physiology and behavior, differences attributed to a single gene may be lost in the noise caused by the heterogeneous genetic background. Therefore an F10 advanced intercross strain between White Leghorn and Red Junglefowl was used to investigate effects of ADRA2C alleles on fear related behaviors and fecundity. We did not find compelling genotype effects in open field, tonic immobility, aerial predator, associative learning or fecundity. Therefore we conclude that ADRA2C is probably not involved in the domestication of the stress response in chicken, and the strong selective sweep is probably caused by selection of some unknown genetic element in the vicinity of the gene.

Show MeSH
Related in: MedlinePlus