The MMADHC Knockout Raji Polyclonal Cells are a CRISPR/Cas9-edited polyclonal knockout cell population derived from the human Raji B lymphoblast cell line, designed for disruption of the MMADHC gene. This polyclonal knockout model enables loss-of-function studies of MMADHC in a B lymphoblast context, providing a versatile tool for investigating intracellular cobalamin metabolism and related disorders. The heterogeneous knockout population is useful for pooled genetic screens or subsequent clonal selection.
The Raji cell line is a well-characterized human B lymphoblast line derived from a Burkitt lymphoma patient, retaining B cell properties including immunoglobulin production and antigen presentation capabilities. These cells lack surface immunoglobulins and carry the Epstein-Barr virus, which contributes to their immortalized state and robust growth in culture. Raji cells are widely used in immunology and hematological malignancy research, and their B cell lineage makes them suitable for studying pathways involved in B cell function and metabolism, including cobalamin processing.
MMADHC encodes a protein critical for intracellular cobalamin (vitamin B12) trafficking, directing cobalamin to methionine synthase (MTR) in the cytosol and methylmalonyl-CoA mutase (MUT) in the mitochondria. MMADHC acts downstream of cobalamin levels and interacts with MMACHC, a partner in cobalamin processing. Disruption of MMADHC impairs the methionine cycle by reducing MTR-mediated homocysteine remethylation, leading to homocysteine accumulation, and hampers MUT-dependent conversion of methylmalonyl-CoA to succinyl-CoA, resulting in methylmalonic acid buildup. This dual metabolic defect mimics the biochemical profile of cblD deficiency, causing combined homocystinuria and methylmalonic aciduria. Transcriptional regulation may involve SP1, though details are under investigation.
In the Raji B lymphoblast background, MMADHC knockout provides a human cell-based model for studying cobalamin metabolism within an immune cell lineage, potentially revealing tissue-specific aspects of cobalamin processing. Raji cells?? robust proliferation and ease of manipulation make them suitable for metabolic flux analyses and for assessing the consequences of cobalamin deficiency on B cell function, including antibody production and antigen presentation. This model enables investigation of how impaired cobalamin trafficking affects cellular methylation capacity, genomic stability, and mitochondrial function in a lymphoid context, which may relate to the pathology of cobalamin disorders.
Researchers can employ this knockout cell population to dissect the biochemical pathways of cobalamin metabolism using assays such as Western blotting for protein expression, liquid chromatography-mass spectrometry (LC-MS) for homocysteine and methylmalonic acid quantification, and enzymatic activity measurements for methionine synthase and methylmalonyl-CoA mutase. Cobalamin trafficking can be monitored via [??Co]-cyanocobalamin uptake and distribution studies, while immunofluorescence enables visualization of MMADHC protein localization. Additionally, these cells can be used to model methylmalonic aciduria with homocystinuria type cblD, screen pharmacological chaperones or small molecules for restoring pathway function, and evaluate proliferation under cobalamin-restricted conditions to probe metabolic dependencies. For further information about this model, please contact Ascent Research.
