SHP2 genetic variants in NSML-associated RASopathies disrupt the PZR-IRX transcription factor signaling axis

Noonan syndrome with multiple lentigines (NSML) is a rare autosomal dominant disorder caused by mutations in PTPN11 (protein tyrosine phosphatase nonreceptor type 11) which encodes for the protein tyrosine phosphatase, SHP2. Approximately 85% of NSML patients develop hypertrophic cardiomyopathy (HCM). Here, we show that SHP2 is recruited to tyrosyl phosphorylated protein-zero related (PZR) in NSML mice. This recruitment is required for the Iroquois homeobox (IRX) transcription factors 3 and 5 to suppress BMP10 which negatively regulates postnatal cardiac growth. The protein expression of IRX3 and IRX5 was elevated in hypertrophied NSML hearts. IRX3 and IRX5 upregulation was rescued in NSML mice harboring a knock-in mutation of PZR that fails to become tyrosyl phosphorylated and recruit SHP2. NSML mice treated with low-dose dasatinib also exhibited normalized IRX3 and IRX5 expression levels. Consistent with this, BMP10 expression levels were reduced in NSML mice and rescued in PZR tyrosyl phosphorylation-deficient and low-dose dasatinib-treated NSML mice. A crystal structure of the tandem SH2 domains of SHP2 bound to tyrosyl phosphorylated PZR reveals that recruitment constrains the open SHP2 conformation to facilitate cellular-Src (c-Src) binding. Disruption of c-Src binding to SHP2 abolished IRX activation and failure to suppress BMP10. Hence, NSML-associated SHP2 genetic variants disrupt IRX transcription factor signaling to BMP10, implicating this axis as a target for RASopathy-associated HCM.