Eggshell gloss is an important characteristic for the manifestation of eggshell appearance. However, no study has yet identified potential candidate genes for eggshell gloss between high-gloss (HG) and low-gloss (LG) chickens. The aim of this study was to perform a preliminary investigation into the formation mechanism of eggshell gloss and to identify potential genes. The eggshell gloss of 300-day-old Rhode Island Red hens was measured from three aspects. Uterine tissues of the selected HG and LG (n = 5) hens were collected for RNA-seq. Blood samples were also collected for whole-genome resequencing (WGRS). RNA-seq analysis showed that 150 differentially expressed genes (DEGs) were identified in the uterine tissues of HG and LG hens. These DEGs were mainly enriched in the calcium signaling pathway and the neuroactive ligand–receptor interaction pathway. Importantly, these two pathways were also significantly enriched in the WGRS analysis results. Further joint analysis of WGRS and RNA-seq data revealed that 5-hydroxytryptamine receptor 1F (HTR1F), zinc finger protein 536 (ZNF536), NEDD8 ubiquitin-like modifier (NEDD8), nerve growth factor (NGF) and calmodulin 1 (CALM1) are potential candidate genes for eggshell gloss. In summary, our research provides a reference for the study of eggshell gloss and lays a foundation for improving egg glossiness in layer breeding.

Background: While the mechanism of asymmetric gonadal development is generally understood, the mechanism of asymmetric oviduct development remains unclear. Methods: Right and left oviducts were collected from chick embryos at three developmental stages (Embryonic day 7.5, E9.5, and E11.5) for RNA-seq analysis (RNA-seq). Whole-genome resequencing (WGRS) was performed on hens with bilateral reproductive systems (a rare natural occurrence) and unilateral controls. These data were co-analyzed with public RNA-seq data of female embryonic gonads at different developmental stages (E4.5, E5.5, and E6.5) to screen for candidate genes affecting oviduct degeneration/development. Results: RNA-seq analyses showed that a total of 27, 10, and 38 DEGs were identified between the left and right oviducts at E7.5, E9.5, and E11.5, respectively. WGRS analyses revealed 1045 differentially mutated genes (DMGs) between bilateral (D) and unilateral (S) groups. Preliminary validation highlighted BMP7, PAK3, SLC6A11, PITX2, and SMC1B as candidate genes influencing oviduct asymmetry. Conclusions: This study provides insights into the genetic basis of asymmetric oviduct development and lays the groundwork for breeding hens with bilateral reproductive systems.