MEKK2 mediates aberrant ERK activation in neurofibromatosis type I

Neurofibromatosis type I (NF1) is characterized by prominent skeletal manifestations caused by NF1 loss. While inhibitors of the ERK activating kinases MEK1/2 are promising as a means to treat NF1, the broad blockade of the ERK pathway produced by this strategy is potentially associated with therapy limiting toxicities. Here, we have sought targets offering a more narrow inhibition of ERK activation downstream of NF1 loss in the skeleton, finding that MEKK2 is a novel component of a noncanonical ERK pathway in osteoblasts that mediates aberrant ERK activation after NF1 loss. Accordingly, despite mice with conditional deletion of Nf1 in mature osteoblasts (Nf1fl/fl;Dmp1-Cre) and Mekk2−/− each displaying skeletal defects, Nf1fl/fl;Mekk2−/−;Dmp1-Cre mice show an amelioration of NF1-associated phenotypes. We also provide proof-of-principle that FDA-approved inhibitors with activity against MEKK2 can ameliorate NF1 skeletal pathology. Thus, MEKK2 functions as a MAP3K in the ERK pathway in osteoblasts, offering a potential new therapeutic strategy for the treatment of NF1.


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Yes, all experiments reported in the manuscript were replicated to confirm reproducibility. 1) Immunoblotting on mouse samples included at least 3 independent experiments, each with consistent results.
2) Animal studies were reproduced across at least 3 independent cohorts.
3) Analysis of serum included at least 8 independent samples and 5 independent samples per each genotype and experimental group, respectively. 4) Ponatinib in vivo treatment were reproduced across three independent experiments. 5) Immunostaining on mouse samples included at least 3 independent experiments and analyzed at least nine independent fields per each genotype and experimental group.
For ponatinib treatment experiments, animals were randomized to treatment vs vehicle groups.
For other experiments, specimen were assigned to group based on genotype.
Yes, µCT analysis, serum assay, and immunohistochemistry were performed by individuals (Alisha R. Yallowitz, Mark Eiseman, Michelle Cung, Ren Xu, Na Li) who were blinded to the nature of the mice under analysis (both what specific mouse strains or treatment groups were in the experiment and whether any individual mouse belonged to control versus experimental groups). The phospho-MEKK2 polyclonal antibody was generated by immunizing rabbit with phospho-MEKK2 peptide.