Blood parameters, single-cell pseudotime trajectory and phagolysosome-related gene expression analysis in crucian carp (Carassius auratus)

Crucian carp (Carassius auratus) is one of the main freshwater cultured fish species in China, and its species degeneration and diseases outbreak for aquaculture brings great economic losses. However, the blood single cellular morphology and molecular identification still needs further investigation in fish. Here, the blood parameters, single-cell types and shapes, physicochemical indexes and phagolysosome (PL)-related gene expression analysis of C. auratus were examined. The results showed that four single-cell types of blood cells, including hematopoietic progenitor cells (HPCs), red blood cells (RBCs), proerythrocytes (PEs) and platelets (PLTs) were identified by pseudotime trajectory analysis in the whole blood and kidney, respectively. The involvement in the PL signaling pathway was significantly observed in GSEA enrichment analysis, and their expression distribution (e.g., CD63, ITGB2, CXCR4b, MMP2, MHCI uka, B2ML, CD74a, FTH1a, COX8b, COX7a2) were evaluated in various tissues. A protein-protein interaction network analysis was performed on the highly expressed cellular markers and co-expressed genes. Moreover, CaCD63 gene cloning and expression, and molecular docking interaction were presented with the integrin (ITGB2) and chemokine receptor (CXCR4b). Overall, this study firstly revealed the molecular marker features of blood cells and provided a valuable reference for further function verification in cyprinid fish.