Mediating ERK1/2 signaling rescues congenital heart defects in a mouse model of Noonan syndrome
Tomoki Nakamura, … , Gerald W. Dorn II, Jeffrey Robbins
Tomoki Nakamura, … , Gerald W. Dorn II, Jeffrey Robbins
Published August 1, 2007
Citation Information: J Clin Invest. 2007;117(8):2123-2132. https://doi.org/10.1172/JCI30756.
View: Text | PDF
Research Article Cardiology

Mediating ERK1/2 signaling rescues congenital heart defects in a mouse model of Noonan syndrome

Abstract

Noonan syndrome (NS) is an autosomal dominant disorder characterized by a wide spectrum of defects, which most frequently include proportionate short stature, craniofacial anomalies, and congenital heart disease (CHD). NS is the most common nonchromosomal cause of CHD, and 80%–90% of NS patients have cardiac involvement. Mutations within the protein tyrosine phosphatase Src homology region 2, phosphatase 2 (SHP2) are responsible for approximately 50% of the cases of NS with cardiac involvement. To understand the developmental stage– and cell type–specific consequences of the NS SHP2 gain-of-function mutation, Q79R, we generated transgenic mice in which the mutated protein was expressed during gestation or following birth in cardiomyocytes. Q79R SHP2 embryonic hearts showed altered cardiomyocyte cell cycling, ventricular noncompaction, and ventricular septal defects, while, in the postnatal cardiomyocyte, Q79R SHP2 expression was completely benign. Fetal expression of Q79R led to the specific activation of the ERK1/2 pathway, and breeding of the Q79R transgenics into ERK1/2-null backgrounds confirmed the pathway’s necessity and sufficiency in mediating mutant SHP2’s effects. Our data establish the developmental stage–specific effects of Q79R cardiac expression in NS; show that ablation of subsequent ERK1/2 activation prevents the development of cardiac abnormalities; and suggest that ERK1/2 modulation could have important implications for developing therapeutic strategies in CHD.

Authors

Tomoki Nakamura, Melissa Colbert, Maike Krenz, Jeffery D. Molkentin, Harvey S. Hahn, Gerald W. Dorn II, Jeffrey Robbins

×

Figure 1

Developmental stage–specific transgene expression of normal or mutant SHP2 in the ventricles.

Options: View larger image (or click on image) Download as PowerPoint
Developmental stage–specific transgene expression of normal or mutant SH...
(A) Schematic diagram of Ptpn11 showing the approximate exon boundaries for the functional domains and location of the Q79R mutation. (B) Constructs used to generate cardiomyocyte-specific expression of normal (WT) or NS mutant Q79R protein. Mouse cDNA containing either normal (WT) or mutant (Q79R) SHP2 was linked to either the β- or α-MHC promoter to express the transgene. The β-MHC promoter expresses the transgene in the ventricular cardiomyocytes between E9.25 and E19, while the α-MHC promoter expresses the transgene in the postnatal ventricle. Vertical boxes in β-MHC and α-MHC promoters represent noncoding exons in 5′-untranslated region. A poly adenylation signal sequence derived from the human growth hormone gene (hGH) was inserted downstream of the cDNA. (C) Western blot analyses of Tg cardiac tissue. In β-MHC hearts, SHP2 protein expression was increased 5.3-fold in both the WT and Q79R Tg hearts at E16.5. SHP2 protein expression was increased 11.4- and 13.6-fold in the α-MHC WT and Q79R hearts, respectively, at 3 months after birth. (D) To confirm that the α-MHC–driven SHP2 construct was transcriptionally inactive during gestation, total SHP2 protein in the Q79R line (13.6-fold overexpression after birth) was measured at E9.5–E16.5, the period during which compaction occurs. When values were normalized to a GAPDH loading control, no statistically significant increases in protein levels were observed.