Genetic variants in SCNN1B and AHCYL1 are associated with eggshell quality in Chinese domestic laying ducks (Anas platyrhynchos)

1. The objective of this study was to investigate the evolution of SCNN1B and AHCYL1 proteins among 10 domestic avian and mammalian animal species, to uncover the expression patterns of SCNN1B and AHCYL1 genes in ducks, identify the genetic variants of the SCNN1B and AHCYL1 genes and analyse their effects on eggshell quality. 2. Expression profiles of the SCNN1B and AHCYL1 genes in Sansui female ducks were determined using real-time fluorescence quantitative PCR to identify SNPs. The duck SCNN1B and AHCYL1 genes were amplified to identify SNPs. A total of 502 Sansui female ducks were genotyped by sequencing, and the associations between the mRNA expression/SNP genotypes and 6 eggshell quality indices were analysed using PASW Statistics 18.0. 3. The results showed that the SCNN1B and AHCYL1 proteins are highly conserved in different mammalian or domestic animals, especially the AHCYL1 protein. The SCNN1B and AHCYL1 genes were widely expressed in different tissues of male and female ducks, and expression level in the uterus was greater than in other tissues. The expression of SCNN1B and AHCYL1 during the oviposition cycle indicated that expression levels were related to the eggshell mineralisation stage. 4. The mRNA expression levels of the uterine SCNN1B and AHCYL1 genes were positively correlated with eggshell strength (ESS), percentage (ESP) and weight (ESW) (P < 0.05), respectively. Ten novel SNPs in SCNN1B and AHCYL1 genes from Chinese domestic laying ducks were identified through PCR amplicon sequencing. 5. Genetic association analysis indicated g.797509 C > T, g.797573 C > T and g.797834 C > T in SCNN1B gene and g.169244 T > A, g.169265 T > C and g.175311 T > C in AHCYL1 gene had a significant effect on eggshell quality. Correlation analysis between the SNP genotype and SCNN1B and AHCYL1 genes expression in the uterus showed that the genotypes of g.797509 C > T, g.797573 C > T, g.797834 C > T, g.169244 T > A and g.175311 T > C sites affected the expression of SCNN1B and AHCYL1 genes in utero (P < 0.05). 6. The study indicated SCNN1B and AHCYL1 as candidate genes to improve eggshell traits in ducks.