Single-cell transcriptome characterization of channel catfish (Ictalurus punctatus) B lymphocyte cell lines

This is the authors' abstract. We don't add key points for this paper.

In channel catfish ( Ictalurus punctatus ), immortalized cell lines that represent different lymphoid cell types have previously been developed and used to study teleost immune function. The 3B11 and 1G8 B cell lines were developed through mitogen stimulation and were the first long-term B cell lines established from an ectothermic vertebrate. In the current study, single-cell RNA sequencing was used to generate high-resolution transcriptional profiles of these catfish B cell lines and compare them to primary splenic B cells. High-quality datasets were obtained for both lines, yielding 9,467 and 9,431 filtered cells, respectively. The two cell lines express canonical B cell markers at different levels and reveal distinct transcriptional identities for both. Immunoglobulin scoring shows that both cell lines retain the ability to express IgD and IgM isotypes. The expression of B-cell developmental genes indicates that neither cell line fully resembles naïve or mature B lymphocytes; instead, both display a lymphoblast/plasmablast phenotype, consistent with their mitogen-driven origins. Cell-cycle scoring revealed widespread S-phase and G2/M activity, reflecting continuous cell proliferation. Oncogenesis-related gene expression included abundant telomerase expression in both cell lines. In comparison there is little to no detectable telomerase expression in the primary splenic B cells, which supports the long-standing hypotheses regarding telomerase-associated immortalization. Together, these results provide a detailed single-cell atlas of catfish B cell lines and offer insight into the cell heterogeneity within these cell culture populations offering new insight into their biology and immortalized state.