Transcription profiling by array of human HEK cells expressing wild type NOD2 or the Crohn's-associated NOD2 variant (L1007fsinsC) under stimulation of bacterial cell wall component muramyl dipeptide (MDP) over a 6-hour time course

NOD2 is an intracellular receptor for the bacterial cell wall component muramyl dipeptide (MDP) and variants of NOD2 are associated with chronic inflammatory diseases of barrier organs e.g. Crohn disease, asthma and atopic eczema. It is known that activation of NOD2 induces a variety of inflammatory and antibacterial factors. The exact transcriptomal signatures that define the cellular programs downstream of NOD2 activation and the influence of the Crohn-associated variant L1007fsinsC are yet to be defined. To describe the MDP-induced activation program, we analyzed the transcriptomal reactions of isogenic HEK293 cells expressing NOD2wt or NOD2L1007fsinsC to stimulation with MDP. Importantly, a clear loss-of-function could be observed in the cells carrying the Crohn-associated variant L1007fsinsC, while the NOD2wt cells showed differential regulation of growth factors, chemokines and several antagonists of NF-κB, e.g. TNFAIP3 (A20) and IER3. To elucidate the MDP-induced activation program we generated isogenic HEK293 cells stably expressing wildtype NOD2 or NOD2L1007fsinsC using a FRT-recombinase based approach. Cells carrying the inserted vector cassette were used as controls (mock-transfectant). To comprehensively analyze NOD2-mediated innate immune responses we analyzed transcriptomal signature patterns using genome-wide cDNA microarrays. Samples were harvested from cell cultures under normal growth conditions 0 h, 2 h and 6 h after MDP‑ stimulation of the cells.