We present the autopsy findings from a Noonan syndrome patient who died as a result of an unusual form of right ventricular obstruction associated with a rare PTPN11 variant previously reported without details of the cardiac findings.
The cutaneous phenotype of NS with a PTPN11 mutation is generally mild and nonspecific, whereas the absence of a PTPN11 mutation is associated with a high frequency of keratinization disorders and hair abnormalities.
Here, imaging and cognitive data were collected from 12 children with PTPN11-related NS, ages 4.0-11.0 years (8.98 ± 2.33) and 12 age- and sex-matched typically developing controls (8.79 ± 2.17).
Gene-related Chinese NS facial features were described using artificial intelligence (AI).NGS identified pathogenic variants in 103 Chinese patients in eight NS-related genes: PTPN11 (48.5%), SOS1 (12.6%), SHOC2 (11.7%), KRAS (9.71%), RAF1 (7.77%), RIT1 (6.8%), CBL (0.97%), NRAS (0.97%), and LZTR1 (0.97%).
Germline mutations in <i>PTPN11</i> gene responsible for catalytic gain- or loss- of function of SHP2 cause two disorders with multiple organ defects, respectively Noonan syndrome (NS) and NS with Multiple Lentigines (NSML).
Different mechanisms of disease have been demonstrated to be associated with the two classes of PTPN11 mutations underlying Noonan syndrome and Noonan syndrome with multiple lentigines (also known as LEOPARD syndrome).
Here, we found that expressing the NS-associated mutant SHP2<sup>D61G</sup> in excitatory, but not inhibitory, hippocampal neurons increased ERK signaling and impaired both long-term potentiation (LTP) and spatial memory in mice, although endogenous SHP2 was expressed in both neuronal types.
One of the most common protein tyrosine phosphatase-2 (SHP2) mutations in Noonan syndrome is the N308D mutation, and it increases the activity of the protein.
A total of 48 clinically diagnosed NS were included, and responsible mutations were identified in 39 patients (81.3%) with PTPN11 mutations being the most prevalent followed by SOS1 mutations.
Previous studies reported that the knock-in mouse models of the mutant D61G of SHP2 exhibited the major features of NS, which demonstrated that the mutation D61G of SHP2 could cause NS.
The scope of cardiac disease in Noonan syndrome is quite variable depending on the gene mutation, with some mutations usually associated with a high incidence of congenital heart defects (PTPN11, KRAS, and others) while those with predominantly hypertrophic cardiomyopathy (HCM) have higher risk and morbidity profiles (RAF1, RIT1, and those associated with multiple lentigines).
Catalytically activating mutations in <i>Ptpn11</i>, which encodes the protein tyrosine phosphatase SHP2, cause 50% of Noonan syndrome (NS) cases, whereas inactivating mutations in <i>Ptpn11</i> are responsible for nearly all cases of the similar, but distinct, developmental disorder Noonan syndrome with multiple lentigines (NSML; formerly called LEOPARD syndrome).
Due to the involvement of SHP2 (SH2 domain-containing protein-tyrosine phosphatase) in human disease, including Noonan syndrome and cancer, several inhibitors targeting SHP2 have been developed.
Weight gain was also negatively influenced by having a PTPN11 mutation (n = 39) and a higher gestational age, whereas children of parents with Noonan syndrome and with a higher birth weight gained more weight.
In conclusion, we demonstrated that hyperactive NS-causing SHP2 mutants impair chondrocyte differentiation during endochondral bone growth through a local hyperactivation of the RAS/ERK signalling pathway, and that statin treatment may be a possible therapeutic approach in NS.