Cellular modeling of Noonan syndrome using human induced pluripotent stem cells

Abstract

Noonan syndrome (NS) is one of developmental disorders caused by heterozygous gain-of-function (GOF) mutations in PTPN11, SOS1, KRAS and RAF1. SHP2 encoded by PTPN11 is commonly associated with NS and result in hyperactivation of Ras-MAPK pathway. Although the hyperactivation of Ras-MAPK pathway is thought to induce low cognitive function in NS patients, cellular mechanisms underlying abnormal development of brain remain elusive. Here, I demonstrate that elevated Ras-MAPK pathway by SHP2 mutation may contribute to abnormal neural differentiation in NS. Induced pluripotent stem cells derived from fibroblast of NS patient (NS-iPSCs) carried a point mutation (c.922 A<G) of PTPN11 revealed early neurodevelopmental defects in embryoid bodies (EBs) by activation of BMP and TGF-β signaling. Inhibition of both BMP and TGF-β signaling pathways in NS-iPSCs rescued aberrant EB morphology and defect of neural rosettes (NRs). Restored NS-NRs normally developed to neural precursor cells (NPCs) despite of increased activities of p-SHP2 and p-ERK. Neural cells differentiated from NS-NPCs (NS-neural cells) exhibited imbalance between neuronal and glial cells, shortened lengths of both dendrites and axons. SHP2-specific inhibition in NS-NPCs led to reduction of biased glial differentiation, and extended lengths of neurites in NS-neural cells. Moreover, the NS-neural cells represented decreased number of extracellular spontaneous firing as well as increased proportion of glial lineages. Collectively, our findings suggest that abnormal activation of Ras-MAPK pathway by NS-associated SHP2 mutation may lead to produce glial lineages during neural differentiation and organize decrease of spontaneous neural activity, which may cause lower cognitive function of NS.