IADR Abstract Archives
Investigation of MORN2 in Response to Oral Pathogen
Objectives: Using gene-centric analysis in the ARIC GWAS cohort we identified MORN2 as a significant susceptibility locus (p=6.2X10-7) for periodontal disease (PD) characterized by high loads of Porphyromonas gingivalis (Pg). This MORN2 locus contained a coding, missense SNP (minor allele frequency=0.23; rs3099950, E -> K). Previous studies indicate that MORN2 facilitates phagocytosis and killing of M. tuberculosis, L. pneumophila and S. aureus in macrophages. We sought to examine whether MORN2 silencing impaired Pg uptake and whether the identified SNP variant resulted in predicted structural alterations in the protein.
Methods: The role of MORN2 was mechanistically explored as a macrophage-mediated mode of bacterial clearance upon challenge with oral bacteria (Pg) in vitro. Silencing (short-hairpin RNA) of endogenous MORN2 in THP-1 monocytes was evaluated via Western blot. The monocytes were challenged with Pg A7436 (at MOI 1:100) and incubated with antibiotics to kill extracellular bacteria. After monocytic lysis, bacterial viability was quantified via CFU counting. The results are expressed as mean % uptake [+/- SD (p< 0.05)], testing for statistical significance by t-test. Molecular modeling of the SNP variant was performed by PyMOL.
Results: MORN2 silenced cells demonstrated suppression of MORN2 by Western blot. As compared to controls, MORN2 silencing resulted in impaired Pg uptake by THP-1 cells. Preliminary results indicate a marked 75% decrease in Pg uptake in MORN2 silenced cells. Molecular models suggest that this variant changes the charge distribution across a PIP3 binding region of the MORN2 structure that may result in impaired membrane interactions and/or phagolysosome fusion.
Conclusions: These data suggest a key role for MORN2 in the phagocytosis-killing of Pg. The identification of a genetic variant of MORN2 provides a foundation for further exploration of the role of this MORN2 genetic variants in Pg mediated dysbiosis in CP and provides an opportunity for gene-based precision periodontal medicine.
Methods: The role of MORN2 was mechanistically explored as a macrophage-mediated mode of bacterial clearance upon challenge with oral bacteria (Pg) in vitro. Silencing (short-hairpin RNA) of endogenous MORN2 in THP-1 monocytes was evaluated via Western blot. The monocytes were challenged with Pg A7436 (at MOI 1:100) and incubated with antibiotics to kill extracellular bacteria. After monocytic lysis, bacterial viability was quantified via CFU counting. The results are expressed as mean % uptake [+/- SD (p< 0.05)], testing for statistical significance by t-test. Molecular modeling of the SNP variant was performed by PyMOL.
Results: MORN2 silenced cells demonstrated suppression of MORN2 by Western blot. As compared to controls, MORN2 silencing resulted in impaired Pg uptake by THP-1 cells. Preliminary results indicate a marked 75% decrease in Pg uptake in MORN2 silenced cells. Molecular models suggest that this variant changes the charge distribution across a PIP3 binding region of the MORN2 structure that may result in impaired membrane interactions and/or phagolysosome fusion.
Conclusions: These data suggest a key role for MORN2 in the phagocytosis-killing of Pg. The identification of a genetic variant of MORN2 provides a foundation for further exploration of the role of this MORN2 genetic variants in Pg mediated dysbiosis in CP and provides an opportunity for gene-based precision periodontal medicine.