Insights into speckled eggs provided by single-cell transcriptomics in high-yield laying hens.

Area of Science:

• Poultry Science
• Genomics
• Cell Biology

Background:

• Eggshell speckle phenotype negatively impacts poultry industry economics and hatchability.
• The genetic basis for eggshell speckling is not fully understood, despite medium heritability.
• Late-laying period increases speckled egg prevalence, causing significant economic losses.

Purpose of the Study:

• To investigate the molecular mechanisms underlying eggshell speckling using single-cell RNA sequencing.
• To identify specific cell types and pathways involved in the speckled eggshell phenotype.
• To provide a single-cell resolution atlas for future research on eggshell quality.

Main Methods:

• Collected uterine tissues from chickens exhibiting different rates of egg speckling.
• Performed 10X Genomics single-cell RNA sequencing to analyze cellular molecular signatures.
• Identified 10 distinct cell types and analyzed gene expression patterns and cellular interactions.

Main Results:

• Identified 10 cell types including immune, endothelial, epithelial, and pigment cells, with consistent distributions between groups.
• Enriched immune cell pathways included IgA production and Toll-like receptor signaling; epithelial cells showed enrichment in TGF-beta, Wnt, and NOD-like receptor signaling.
• Secreted phosphoprotein 1 (SPP1) was down-regulated in all cell types in the speckled group; cell proliferation pathways were inhibited, while cell migration interactions were activated.

Conclusions:

• Single-cell analysis revealed heterogeneity and cell-type-specific patterns in eggshell speckling.
• Down-regulation of SPP1 and altered signaling pathways in immune and epithelial cells are associated with the speckled phenotype.
• Findings provide a foundation for understanding the cellular basis of eggshell quality and developing targeted interventions.