PTPN11 and Noonan syndrome: Similar to NF1, gain of function mutations in protein-tyrosine phosphatase nonreceptor-type 11 (PTPN11, SHP2) enhance ERK signaling in osteoblasts, causing Noonan syndrome associated with impaired skeletal mineralization and short stature (Binder, 2009; Choudhry et al., 2012; Roberts et al., 2007).