C4BPA Knockout HAP1 Polyclonal Cells are a CRISPR/Cas9-edited polyclonal cell population derived from the HAP1 human near-haploid cell line, featuring targeted disruption of the C4BPA gene. This knockout model provides a loss-of-function tool for studying the alpha chain of complement 4 binding protein (C4BP) in a simplified genetic background. The polyclonal format comprises a pool of cells carrying heterogeneous mutations at the target locus, ensuring robust ablation of gene function without the need for single-cell cloning. This population is suitable for bulk functional assays, pooled genetic screens, and complement pathway analysis.
HAP1 is a near-haploid human myeloid leukemia cell line originally derived from the chronic myeloid leukemia (CML) KBM-7 line. It possesses a single copy of most chromosomes, which facilitates the generation of null phenotypes via CRISPR/Cas9-mediated disruption of a single allele. This haploid nature eliminates the complexity of heterozygous genotypes, enabling straightforward interpretation of gene function, particularly in functional genomics and cancer biology studies. HAP1 cells have been widely adopted as a model system for high-throughput genetic screening and for investigating signaling networks relevant to myeloid malignancies.
The C4BPA gene encodes the alpha chain of the soluble complement regulator C4BP, which is essential for controlling the classical and lectin complement pathways. C4BPA protein forms complexes with C4BPB and circulates in plasma, where it binds to complement component C4b. As a cofactor for complement factor I, C4BPA accelerates the proteolytic inactivation of C4b, leading to the decay of the C3 convertase (C4b2a) and subsequent suppression of C3a and C5a anaphylatoxin generation and membrane attack complex formation. This regulatory activity is modulated by interactions with protein S and heparin. Expression of C4BPA is transcriptionally upregulated by pro-inflammatory stimuli, including interleukin-6 (IL-6), interferon-gamma (IFN-??), and tumor necrosis factor-alpha (TNF-??), which signal through STAT3 and other pathways, placing C4BPA at the intersection of inflammation and complement regulation.
Disruption of C4BPA in HAP1 cells eliminates the endogenous capacity to regulate complement activation, creating a clean cellular background for dissecting complement effector functions and studying how myeloid leukemia cells may dysregulate complement control to evade immune-mediated damage. Given the role of chronic inflammation in CML progression, this knockout model offers a relevant system to examine the consequences of lost complement regulation on tumor cell survival and inflammatory signaling.
This C4BPA polyclonal knockout population can be applied to a variety of research contexts, including functional validation of C4BPA as a drug target in complement-driven diseases such as atypical hemolytic uremic syndrome, preeclampsia, and systemic lupus erythematosus. It is also valuable for performing haploid genetic screens to identify novel regulators of the complement system and for studying immune evasion mechanisms in cancer. Experimental readouts may include C4b binding assays, C3 convertase decay acceleration assays, factor I cofactor activity assays, and hemolytic complement tests. Additional characterization using flow cytometry, RT-qPCR, and ELISA can quantify C4BP expression and complement activation products. For further details, please contact Ascent Research.
