The DNTT Knockout HAP1 Polyclonal Cells represent a CRISPR/Cas9-edited polyclonal knockout cell population designed to ablate expression of the DNTT gene, which encodes terminal deoxynucleotidyl transferase (TdT). This loss-of-function model is generated in the HAP1 near-haploid human cell line, providing a genetically tractable system for investigating the roles of TdT in DNA repair and lymphocyte development. The polyclonal format ensures a diverse pool of edited alleles, facilitating robust functional studies without the selection bias of single-cell clones.
HAP1 cells are a near-haploid chronic myeloid leukemia (CML) cell line originally derived from the KBM-7 line. Their haploid karyotype simplifies genetic manipulation and phenotype interpretation, making them a powerful tool for functional genomics and large-scale genetic screening. The CML background also provides a relevant context for studying hematological malignancies and leukemia-associated pathways.
The DNTT gene product, TdT, catalyzes the template-independent addition of random nucleotides (N-additions) at V(D)J recombination junctions during lymphocyte development, thereby generating immunoglobulin and T-cell receptor diversity. TdT function is tightly coordinated with the non-homologous end joining (NHEJ) machinery. Upstream, TdT expression is regulated by the RAG1/RAG2 recombinase, the E2A transcription factor, EBF1, and PAX5. During repair, TdT interacts with Ku70, Ku80, XRCC4, LIG4, and DNA-PKcs to insert nucleotides at DNA breaks. Its downstream effect is increased junctional diversity of antigen receptor genes. This mechanism is central to adaptive immunity, and its dysregulation is implicated in acute lymphoblastic leukemia, severe combined immunodeficiency, and lymphomas.
In the HAP1 cellular context, disruption of DNTT creates a valuable model to dissect the NHEJ pathway and V(D)J recombination process in a simplified genetic environment. Because HAP1 cells are near-haploid, DNTT knockout effects are unambiguous, allowing clear assessment of its role in DNA repair fidelity and lymphocyte-specific processes. This model is particularly useful for exploring how TdT contributes to leukemia development, as CML cells share molecular features with lymphoid malignancies. Researchers can use these cells to study how loss of TdT impacts NHEJ efficiency and whether compensatory mechanisms emerge.
A wide range of experimental applications are enabled by this knockout model. Western blotting can confirm TdT loss, while TdT enzymatic activity assays directly measure catalytic function. NHEJ reporter assays evaluate DNA repair kinetics, and PCR-based V(D)J recombination assays assess junctional diversity in lymphocyte-derived cells. Flow cytometry for lymphocyte markers can be used if differentiation protocols are applied. Moreover, these cells are compatible with haploid genetic screens to identify novel modulators of NHEJ or synthetic lethal interactions in leukemia. For additional information or to request a quote, please contact Ascent Research.
