The C1orf21 Knockout HAP1 Polyclonal Cells product comprises a CRISPR/Cas9-edited polyclonal population of HAP1 cells with disruption of the C1orf21 gene. This polyclonal knockout pool provides a genetically heterogeneous model for studying C1orf21 loss, eliminating need for single-cell cloning while maintaining the near-haploid background ideal for functional genomics screens. The CRISPR/Cas9 approach targets C1orf21, which encodes PIGK, the catalytic subunit of the GPI transamidase complex. Supplied as a proliferating polyclonal population, it enables direct use in biochemical, cell-based, and genetic assays investigating GPI anchor biosynthesis and disease.
HAP1 cells are a near-haploid human cell line derived from KBM-7 chronic myeloid leukemia cells with adherent fibroblastoid morphology. Their haploidy facilitates straightforward loss-of-function studies via single mutagenic events, making HAP1 ideal for CRISPR/Cas9-mediated gene disruption and haploid genetic screens. Widely used in functional genomics and cancer research, this cell line offers a robust platform to study knockout phenotypes in a well-characterized cancer model.
C1orf21 encodes PIGK, the catalytic subunit of the GPI transamidase, which cleaves C-terminal signal peptides and attaches pre-assembled GPI anchors to proteins. This complex includes essential interacting partners GPAA1, PIGT, PIGS, and PIGU. GPI anchoring delivers proteins to the cell surface; substrates include CD55, CD59, alkaline phosphatase, Thy-1, prion protein, and uPAR. Upstream GPI biosynthesis involves PIGA, PIGC, PIGH, PIGP, PIGQ, PIGY, and DPM2, and is regulated by transcription factors such as Sp1 and NF-Y. Disruption of PIGK prevents GPI attachment, causing loss of surface GPI-anchored proteins and potential defects in signaling, adhesion, and immune regulation.
In HAP1 cells, C1orf21 knockout models GPI anchor deficiency, with loss of complement regulators CD55 and CD59 rendering cells susceptible to lysis, mirroring aspects of PNH and inherited GPI deficiencies. The near-haploid background ensures uniform phenotypic penetrance in the polyclonal population, facilitating quantitative assays of GPI-AP function in cancer cell signaling, adhesion, and immune evasion.
Applications include studying GPI anchor biosynthesis and protein trafficking, modeling inherited GPI deficiency and neurodevelopmental disorders, and screening for complement-mediated cytoprotection. Typical assays: flow cytometry for CD55/CD59 surface expression, western blotting, PI-PLC release, alkaline phosphatase activity, immunofluorescence, complement lysis, RNA-seq, and trafficking assays. For further details, please contact Ascent Research.
