The ALG9 Knockout HT29 Polyclonal Cells are a CRISPR/Cas9-edited polyclonal knockout cell population derived from the HT29 human colorectal adenocarcinoma line, designed for loss-of-function studies of the ALG9 gene. This heterogeneous pool of cells provides a robust model to investigate alpha-1,2-mannosyltransferase function in N-glycosylation without clonal bias, facilitating physiologically relevant analysis of glycoprotein processing defects.
The HT29 host cell line is an established human colorectal adenocarcinoma model that retains features of intestinal epithelial cells, including polarized morphology and brush-border enzymes. Its active secretory pathway and glycosylation machinery render it well-suited for examining how N-glycan biosynthesis disruptions affect cell surface receptor display, adhesion, and signaling.
ALG9 encodes an endoplasmic reticulum (ER)-resident alpha-1,2-mannosyltransferase that catalyzes the sequential addition of mannose residues to the dolichol-linked oligosaccharide intermediate Man6GlcNAc2-PP-dolichol, yielding the Man9GlcNAc2-PP-dolichol precursor. This enzyme functions downstream of dolichol phosphate and GDP-mannose, working in concert with ALG3, ALG6, and ALG12 within the ER membrane. ALG9 expression is positively regulated by unfolded protein response (UPR) transcription factors ATF6 and XBP1 and is sensitive to cellular mannose availability. Disruption of ALG9 leads to accumulation of truncated lipid-linked oligosaccharides, impaired transfer of the mature glycan to nascent polypeptides by the oligosaccharyltransferase complex, and consequent activation of ER quality control and UPR signaling.
In HT29 colorectal adenocarcinoma cells, ALG9 knockout drastically remodels the cell-surface glycocalyx and glycosylation of critical receptors, impacting ligand recognition, cell adhesion, and immune surveillance. The ensuing ER stress, detected by elevated GRP78/BiP and other UPR markers, can modulate oncogenic signaling networks and tumor cell behavior. This model system is therefore instrumental for dissecting the molecular pathology of ALG9-congenital disorder of glycosylation (CDG type IL) and for probing the role of N-glycan defects in cancer progression and therapeutic response.
Typical experimental applications include monitoring ER stress via western blotting or RT-qPCR for UPR target genes, conducting N-glycan structural profiling by mass spectrometry, and evaluating surface glycosylation alterations using lectin blotting with concanavalin A or L-PHA or by flow cytometry. The cells also support HPLC-based analysis of dolichol-linked oligosaccharide intermediates, glycoprotein quality control assays, and drug target validation studies aimed at restoring glycosylation. For further details, contact Ascent Research.
