MEK-ERK pathway modulation ameliorates disease phenotypes in a mouse model of Noonan syndrome associated with the Raf1L613V mutation
Xue Wu, … , Benjamin G. Neel, Toshiyuki Araki
Xue Wu, … , Benjamin G. Neel, Toshiyuki Araki
Published March 1, 2011; First published February 21, 2011
Citation Information: J Clin Invest. 2011;121(3):1009-1025. https://doi.org/10.1172/JCI44929.
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Category: Research Article

MEK-ERK pathway modulation ameliorates disease phenotypes in a mouse model of Noonan syndrome associated with the Raf1L613V mutation

Abstract

Hypertrophic cardiomyopathy (HCM) is a leading cause of sudden death in children and young adults. Abnormalities in several signaling pathways are implicated in the pathogenesis of HCM, but the role of the RAS-RAF-MEK-ERK MAPK pathway has been controversial. Noonan syndrome (NS) is one of several autosomal-dominant conditions known as RASopathies, which are caused by mutations in different components of this pathway. Germline mutations in RAF1 (which encodes the serine-threonine kinase RAF1) account for approximately 3%–5% of cases of NS. Unlike other NS alleles, RAF1 mutations that confer increased kinase activity are highly associated with HCM. To explore the pathogenesis of such mutations, we generated knockin mice expressing the NS-associated Raf1L613V mutation. Like NS patients, mice heterozygous for this mutation (referred to herein as L613V/+ mice) had short stature, craniofacial dysmorphia, and hematologic abnormalities. Valvuloseptal development was normal, but L613V/+ mice exhibited eccentric cardiac hypertrophy and aberrant cardiac fetal gene expression, and decompensated following pressure overload. Agonist-evoked MEK-ERK activation was enhanced in multiple cell types, and postnatal MEK inhibition normalized the growth, facial, and cardiac defects in L613V/+ mice. These data show that different NS genes have intrinsically distinct pathological effects, demonstrate that enhanced MEK-ERK activity is critical for causing HCM and other RAF1-mutant NS phenotypes, and suggest a mutation-specific approach to the treatment of RASopathies.

Authors

Xue Wu, Jeremy Simpson, Jenny H. Hong, Kyoung-Han Kim, Nirusha K. Thavarajah, Peter H. Backx, Benjamin G. Neel, Toshiyuki Araki

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Figure 9

MEK inhibitor treatment rescues growth defect and cardiac hypertrophy in L613V/+ mice.

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MEK inhibitor treatment rescues growth defect and cardiac hypertrophy in...
Mice were injected i.p. daily with PD0325901 (PD; 5 mg/kg BW) or vehicle, starting at 4 weeks of age and for the succeeding 6 weeks. Body length (A) and BW (B) were measured weekly. Note the rapid normalization of body length, as well as the increase in BW caused by inhibitor treatment. #P < 0.05, ##P < 0.005, ###P < 0.0001, 2-way repeated-measures ANOVA; *P < 0.05, **P < 0.005, ***P < 0.0001, Bonferroni post-test when ANOVA was significant (black symbols, WT PD vs. WT control; red symbols, L613V/+ PD vs. L613V/+ control). (C) Heart weight/BW ratio and (D) LVPWd were restored to within normal limits in inhibitor-treated mice. **P < 0.005, ***P < 0.0001, Bonferroni post-test when ANOVA was significant; #P < 0.05, 1-tailed Student’s t test. (E) LVIDd. **P < 0.005, Bonferroni post-test when ANOVA was significant; #P < 0.05, ##P < 0.005, 1-tailed Student’s t test. n = 14 (WT); 10 (L613V/+); 6 (WT PD); 14 (L613V/+ PD). (F) Cross-sectional area of cardiomyocytes (original magnification, ×400; scale bar, 100 μm), measured in WGA-strained heart sections (n = 2 samples per group, with 200 cells counted per sample using ImageJ). ***P < 0.0001, Bonferroni post-test when ANOVA was significant. See also Supplemental Figure 6.