The effect of a domestication related mutation in the thyroid stimulating hormone receptor (TSHR) on photoperiodic response and reproduction in chicken
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The thyroid stimulating hormone receptor (TSHR) has been suggested to be a “domestication locus” in the chicken. A strong selective sweep over the gene in domestic breeds of chicken, but not in the ancestral Red Junglefowl, and significant effects of a mutation in TSHR on domestication related traits in chicken, indicate that the gene has been important for the chicken domestication. The TSHR play a key role in the signal transduction of seasonal reproduction, which is characteristically less strict in domestic animals. We investigated the effect of the mutation on reproductive traits as well as TSHB, TSHR, DIO2 and DIO3 gene expression during altered day length (photoperiod) in females and males intercross chickens homozygous for the mutation (d/d) or wild type homozygotes (w/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 TSHR gene expression was significantly lower in both d/d females and males, in comparison to w/w individuals, indicating a strong effect of the “domestic” mutation on gene expression. The d/d females showed a faster increase in the onset of laying than w/w females, and d/d males showed a reduced response to altered day length in testicular size and significant lower levels of TSHB and DIO3 expression, in comparison to w/w males. Additionally, pure White Leghorn females kept under natural day length in Sweden during December showed active ovaries and significant lower levels of TSHR and DIO3 expression in comparison to Red Junglefowl females kept under similar conditions. Our study suggest that the TSHR mutation affects photoperiodic response in chicken in the direction of being less dependent on seasonal reproduction, a typical domestication feature, and may therefore have been important for the chicken domestication.
Developmental Biology Cell and Molecular Biology Other Biological Topics
IdentifiersURN: urn:nbn:se:liu:diva-112867OAI: oai:DiVA.org:liu-112867DiVA: diva2:773141