Tnfsf11 Knockout MLO-Y4 Cell Line

The Tnfsf11 Knockout MLO-Y4 Cell Line is a CRISPR/Cas9-edited mouse osteocyte-like cell line with targeted disruption of the Tnfsf11 gene, leading to abrogation of RANKL protein expression. This loss-of-function model eliminates the key cytokine required for osteoclast differentiation and activation, providing a defined platform for probing RANKL-dependent signaling pathways.

The parental MLO-Y4 line is an immortalized osteocyte-like cell model derived from transgenic mice expressing SV40 large T antigen. These cells retain a dendritic morphology and expression of osteocyte markers, functioning as mechanosensory cells that regulate bone remodeling by controlling osteoblast and osteoclast activity. MLO-Y4 cells endogenously produce RANKL in response to mechanical and hormonal stimuli, making them a physiologically relevant host for gene knockout studies.

Tnfsf11 encodes RANKL, a type II transmembrane protein that binds to the RANK receptor on osteoclast precursors, recruiting TRAF6 and triggering activation of NF-??B and MAPK (JNK, p38, ERK) cascades. These signals induce NFATc1, the master transcription factor for osteoclastogenesis, which upregulates genes such as Acp5 (TRAP), Ctsk (cathepsin K), and Calcr (calcitonin receptor). RANKL activity is inhibited by the soluble decoy receptor OPG, and its expression is stimulated by osteotropic factors including PTH, 1,25-dihydroxyvitamin D3, IL-6, and TNF-??, integrating local and systemic bone remodeling signals.

In osteocytes, Tnfsf11 expression is a critical node coupling mechanical sensing to bone resorption. Osteocyte-derived RANKL is a dominant source in adult bone remodeling, and its dysregulation contributes to pathologies such as osteoporosis and bone metastasis. The Tnfsf11 knockout in MLO-Y4 cells allows dissection of osteocyte-specific RANKL functions in co-culture systems, eliminating confounding RANKL from other cell types, and facilitates study of RANKL reverse signaling potential in osteocytes.

This cell line supports diverse applications, including co-culture osteoclastogenesis assays with TRAP staining, NF-??B/NFATc1 luciferase reporter assays, and qPCR/western blot analysis of osteoclast markers (NFATc1, TRAP, cathepsin K) and signaling intermediates (TRAF6, c-Fos). ELISA for secreted RANKL/OPG confirms knockout efficacy, while transwell migration assays evaluate osteoclast precursor recruitment. The line is also suitable for drug screening of anti-resorptive agents and RNA-seq to identify RANKL-dependent transcriptomic changes. For additional information, please contact Ascent Research.