Single-cell landscape of goose thymus uncovers developmental and regulatory dynamics of T cell differentiation

The thymus is vital for T cell development, yet avian thymocyte maturation remains poorly characterized. Here, we present a single-cell transcriptomic atlas of thymic development in Zhedong White geese across embryonic, gosling, juvenile, and adult stages. Morphological and histological analysis revealed a multilobulated, paired thymus with rapid post-hatch expansion and age-dependent involution. Single-cell RNA sequencing identified all major thymic cell types, with T cells predominant and γδ T cells unusually abundant compared to mammals. High-resolution profiling defined key T cell subsets and reconstructed sequential differentiation, showing DN cells transition from pre-commitment states marked by BCL11A, SPI1, and HHEX to committed states (BCL11B, TCF7) and β-selection gene activation. Thymic epithelial cells functioned as central signaling hubs, mediating microenvironmental regulation. Comparative analysis with human and mouse thymus revealed a conserved developmental framework, yet pronounced species-specific differences at the DP stage and in γδ T cell enrichment. These findings contribute foundational insights for avian immunology and poultry breeding.