Partial duplication of the PRLR and SPEF2 genes at the late feathering locus in chicken.

BACKGROUND: One of the loci responsible for feather development in chickens is K. The K allele is partially dominant to the k+ allele and causes a retard in the emergence of flight feathers at hatch. The K locus is sex linked and located on the Z chromosome. Therefore, the locus can be utilized to produce phenotypes that identify the sexes of chicks at hatch. Previous studies on the organization of the K allele concluded the integration of endogenous retrovirus 21 (ev21) into one of two large homologous segments located on the Z chromosome of late feathering chickens. In this study, a detailed molecular analysis of the K locus and a DNA test to distinguish between homozygous and heterozygous late feathering males are presented. RESULTS: The K locus was investigated with quantitative PCR by examining copy number variations in a total of fourteen markers surrounding the ev21 integration site. The results showed a duplication at the K allele and sequence analysis of the breakpoint junction indicated a tandem duplication of 176,324 basepairs. The tandem duplication of this region results in the partial duplication of two genes; the prolactin receptor and the gene encoding sperm flagellar protein 2. Sequence analysis revealed that the duplication is similar in Broiler and White Leghorn. In addition, twelve late feathering animals, including Broiler, White Leghorn, and Brown Layer lines, contained a 78 bp breakpoint junction fragment, indicating that the duplication is similar in all breeds. The breakpoint junction was used to develop a TaqMan-based quantitative PCR test to allow distinction between homozygous and heterozygous late feathering males. In total, 85.3% of the animals tested were correctly assigned, 14.7% were unassigned and no animals were incorrectly assigned. CONCLUSION: The detailed molecular analysis presented in this study revealed the presence of a tandem duplication in the K allele. The duplication resulted in the partial duplication of two genes; the prolactin receptor and the gene encoding sperm flagellar protein 2. Furthermore, a DNA test was developed to distinguish between homozygous and heterozygous late feathering males.

Across-line SNP association study for (innate) immune and behavioral traits in laying hens.

BACKGROUND: An association study between single nucleotide polymorphism markers (SNP) and (innate and adaptive) immune parameters but also feather condition score on the back, rump and belly of laying hens was performed. The immune parameters measured in blood samples were natural and acquired antibody titers and complement activity. Feather condition score as a measure of feather damage was determined, this parameter is closely related to feather pecking behavior in hens housed in groups.The aim of the study was to detect associations between genetic markers and immune parameters and feather condition score across nine lines of laying hens, focusing on the feather peckers as well as on the victims of feather pecking. METHODS: A novel approach based on across-line analysis and testing of the SNP-by-line interaction was performed. RESULTS: In total 59 significant associations between SNP and immune traits were detected. Previously identified QTL were confirmed and new associations of genes regulating immune function identified. The IL17A gene (chromosome 3) influences natural and acquired antibody titers and activation of classical and alternative complement pathways. The major histocompatibility complex on chromosome 16 showed significant association with natural and acquired antibody titers and classical complement activity. The IL12B and IRF1 genes on chromosome 13 were associated with natural antibody titers.The direct effect of the genotype of an individual on its feather condition and the associative effect of the genotype of the cage mates on the individual's feather condition were analyzed. The direct genetic effect can be described as the susceptibility to be pecked at, and the associative genetic effect as the propensity to perform feather pecking. Eleven significant associations were detected for the direct effect, and 81 for the associative effect. The serotonin receptor 2C (HTR2C) on chromosome 4 was highlighted in both analyses. CONCLUSIONS: Our results confirmed previously identified QTL and identified new associations of genes regulating immune function. The results for feather condition score supports existing evidence of involvement of the serotonergic system in feather pecking in laying hens. Immune regulatory genes were found to be associated to feather condition score, revealing relationships between the immune system and behavior.