ASS1 knockout HAP1 polyclonal cells consist of a CRISPR/Cas9-edited heterogeneous population in which the human ASS1 gene has been disrupted. Derived from the near-haploid HAP1 cell line, these cells provide a ready-to-use loss-of-function model, avoiding the need for clonal isolation while still achieving potent target gene inactivation. The polyclonal format preserves genetic diversity, making it suitable for pooled functional assays and screens where population-level phenotypes are assessed.
The HAP1 cell line is a male, near-haploid, fibroblast-like line derived from the KBM-7 chronic myelogenous leukemia (CML) cell line. Its haploid genome simplifies genetic engineering, as modification of a single allele often yields a complete knockout. Widely employed in CRISPR screens, HAP1 cells offer stable growth, high transduction efficiency, and reliable performance in arrayed and pooled formats, making them a cornerstone for functional genomics and drug target discovery.
The ASS1 gene encodes argininosuccinate synthase, which catalyzes the conversion of citrulline and aspartate to argininosuccinate in the urea cycle. This reaction is essential for arginine biosynthesis and ammonia detoxification. ASS1 is transcriptionally regulated by glucocorticoids, insulin, and factors including C/EBP and HNF4??, and is often silenced by promoter methylation in cancer. The enzyme interacts with ASL and HSP90 to channel metabolites, and its activity generates arginine, the substrate for nitric oxide synthases (NOS1-3) and polyamine production. Disruption of ASS1 thus eliminates arginine synthesis and downstream nitric oxide and polyamine outputs.
In the HAP1 background, ASS1 knockout produces a stringent model of arginine auxotrophy, mirroring citrullinemia type I and the metabolic dependency observed in ASS1-deficient cancers (e.g., melanoma, hepatocellular carcinoma). The haploid karyotype ensures complete loss of enzyme function, facilitating clear analysis of urea cycle defects and cellular responses to arginine starvation. This system is valuable for investigating therapeutic strategies such as arginine-deprivation therapy and the metabolic adaptations of ASS1-negative tumors.
Assays for this model include western blotting and RT-qPCR for knockout confirmation, arginine deprivation viability assays to measure auxotrophy, and LC-MS-based citrulline quantification for metabolic profiling. Griess assays quantify nitric oxide levels, while apoptosis assays and synthetic lethality screens under arginine-limited conditions probe cell death pathways. These cells also support drug target validation and urea cycle flux studies. For further information, please contact Ascent Research.
