Molecular cloning, expression and association study with reproductive traits of the duck LRP8 gene.

1. Two splice variants of duck LRP8 were identified, one containing 8 ligand-binding repeats (LRP8-1) and the other containing only 7 repeats (LRP8-2). The two transcripts share ~71-91% nucleic acid identity and ~65-94% amino acid identity with their counterparts in other species. A phylogenetic tree based on amino acid sequences shows that duck LRP8 proteins are closely related to those of chicken, turkey and zebra finch. 2. The semi-quantitative reverse transcription polymerase chain reaction (RT-PCR )analysis indicates that the two transcripts are expressed in all the examined tissues, and the LRP8-1 transcript is more highly expressed in hypothalamus, ovary and pituitary gland than in other detected tissues. 3. Six single nucleotide polymorphisms (SNPs) were identified in the coding region. Association analysis demonstrated that the c.528C > T genotypes were associated with egg production (EP) (EP210d, EP300d and EP360d), age at laying the first egg (AFE) and body weight at sexual maturity (BWSM). The c.1371A > G genotypes were associated with egg production (EP210d, EP300d and EP360d). 4. The haplotypes of c.528C > T and c.1371A > G were associated with EP (EP210d, EP300d and EP360d), yolk weight (YW), albumen weight (AW), egg weight (EW), BWSM and the first egg weight (FEW). 5. Duck LRP8 gene was associated with some reproductive traits and is an important candidate gene for the genetic selection of improved reproductive traits.