A novel intron variant in the prolactin gene associated with eggshell weight and thickness with putative alternative splicing patterns in chickens

Raising Iraqi indigenous chickens (IIC) is restricted by their thin and low eggshell weights. Due to the importance of the prolactin (Prl) gene in regulating a wide range of egg production traits, this study assessed the potential genetic polymorphisms associated with Prl that may influence these traits. The polymorphism was examined in three Prl loci of the IIC breed (n = 120) in comparison with the standard Hyline breed (n = 120). The polymorphism of both breeds was associated with eggshell weight and thickness indices for 16 weeks, starting from the 44th to the 59th week. After genotyping three loci within Prl by polymerase chain reaction-single-stranded conformation polymorphism (SSCP) method, only one novel SNP was identified in intron 4, namely 129G > A. The identified intron SNP exerted a significant association with both eggshell thickness and weight indices throughout the investigation period. Birds with GG genotype exhibited higher indices of eggshell thickness and weight than those with the GA and AA genotypes, respectively. The employed in silico tools predicted a remarkable ability for the identified SNP to alter the mRNA splicing pattern, which might be related to altered prolactin activity in birds having an alternative allele A. This study is the first to suggest the significance of this novel intron SNP in assessing eggshell traits in chickens.