Cloning and tissue expression profiling of the <i>GnRHR</i> gene of the Muscovy duck (<i>Cairina moschata</i>): polymorphism and association with egg-laying performance

1. cDNA sequence of gonadotropin-releasing-hormone receptor (<i>GnRHR</i>) gene was cloned and an association analysis between mutations and laying performance was conducted.2. A 1680-bp cDNA sequence of Muscovy duck <i>GnRHR</i>, which encodes 415 amino acids, was obtained and characterised. Phylogenetic analysis revealed that Muscovy duck <i>GnRHR</i> has a close relationship with <i>Gallus gallus GnRHR</i>.3. There were significantly different expression profiles between 4 age periods in the hypothalamus, pituitary, and ovary. The expression of <i>GnRHR</i> at the age of 36 weeks (laying period) was higher than other time points in the three tissues. <i>GnRHR</i> was expressed in 12 different tissues. The highest expression levels were observed in hypothalamus, pituitary and gonads.4. A single nucleotide polymorphism detected in the second intron was associated with egg-laying performance. Individuals with genotype TT had better egg-laying performance from individuals with genotypes CC or TC. Therefore, <i>GnRHR</i> could be used as a marker gene for laying performance in Muscovy duck.