The CSK Knockout Raji Polyclonal Cells are a polyclonal population of Raji B lymphoblasts generated via CRISPR/Cas9-mediated disruption of the CSK gene. This product eliminates endogenous CSK expression, creating a loss-of-function model that retains the inherent genetic diversity of the Raji cell line. The polyclonal format avoids clonal artifacts and is optimized for studies requiring bulk analysis of B cell signaling, such as immunoblotting and phospho-flow cytometry.
The Raji cell line is an Epstein-Barr virus-immortalized B lymphoblastoid line derived from a Burkitt’s lymphoma patient. It stably expresses the B cell markers CD19 and CD20 and exhibits high proliferative capacity and facile genetic tractability. As a well-established model for B cell biology and lymphomagenesis, Raji cells provide a relevant background for interrogating CSK function in immune and oncogenic signaling.
CSK (C-terminal Src kinase) serves as a pivotal negative regulator of Src family kinases (SFKs). It phosphorylates the conserved C-terminal inhibitory tyrosine residue??such as Y507 of LYN??maintaining these kinases in an autoinhibited, inactive state. CSK is activated downstream of integrin engagement, receptor tyrosine kinases, and SH3 domain-containing adaptors, and it physically interacts with regulatory proteins including PTPN22, CBP/PAG, paxillin, and focal adhesion kinase (FAK). In the B cell receptor (BCR) signaling cascade, CSK functions upstream of LYN, which in turn governs the activation of SYK, PLC??2, the MAPK pathway, and NF??B, thereby modulating immune receptor thresholds, adhesion dynamics, and cytoskeletal reorganization.
Knocking out CSK in Raji B cells removes this inhibitory constraint, leading to constitutive activation of LYN and other SFKs. The resulting persistent SFK signaling drives antigen-independent BCR signal transduction, promoting hyperphosphorylation of downstream kinases and adaptors, as well as transcriptional programs associated with proliferation and survival. This polyclonal knockout model recapitulates key aspects of B cell hyperactivation found in autoimmune disorders such as systemic lupus erythematosus and in B cell lymphomas, making it a valuable system for studying pathogenic signaling and for evaluating pharmacological SFK inhibitors.
Representative applications include detailed mechanistic dissection of BCR signaling, quantitative phospho-flow analysis of SFK activation status, and high-throughput screening of SFK-targeting compounds. Researchers can employ Western blotting to monitor LYN phosphorylation at Y507, flow cytometry to measure upregulation of activation markers CD69 and CD86, and calcium flux assays to assess BCR responsiveness. Complementarily, proliferation and apoptosis assays report on functional outcomes, while RNA-seq captures global transcriptomic changes. For further information or technical assistance, please contact Ascent Research.
