Noonan syndrome gain-of-function mutations in NRAS cause zebrafish gastrulation defects

• Published in: Disease models & mechanisms Vol. 4; no. 3; pp. 393 - 399
• Main Authors: Runtuwene, Vincent, van Eekelen, Mark, Overvoorde, John, Rehmann, Holger, Yntema, Helger G, Nillesen, Willy M, van Haeringen, Arie, van der Burgt, Ineke, Burgering, Boudewijn, den Hertog, Jeroen
• Format: Journal Article
• Language: English
• Published: England The Company of Biologists Ltd 01-05-2011; The Company of Biologists Limited; The Company of Biologists
• Subjects: Amino Acid Substitution; Amino acids; Animals; Base Sequence; Cell Movement; Craniofacial Abnormalities - embryology; Craniofacial Abnormalities - metabolism; Craniofacial Abnormalities - pathology; Developmental disabilities; Embryo, Nonmammalian - abnormalities; Embryo, Nonmammalian - metabolism; Embryo, Nonmammalian - pathology; Fibroblasts; Gastrulation - genetics; Humans; Molecular Sequence Data; Mutation; Mutation - genetics; Noonan Syndrome - genetics; Noonan's syndrome; Oncogene Proteins - genetics; Oncogene Proteins - metabolism; Patients; Phosphorylation; Protein Transport; Proteins; ras Proteins - genetics; ras Proteins - metabolism; Signal Transduction; Zebrafish - embryology; Zebrafish - metabolism
• ISSN: 1754-8403; 1754-8411
• DOI: 10.1242/dmm.007112

Noonan syndrome is a relatively common developmental disorder that is characterized by reduced growth, wide-set eyes and congenital heart defects. Noonan syndrome is associated with dysregulation of the Ras-mitogen-activated-protein-kinase (MAPK) signaling pathway. Recently, two mutations in NRAS were reported to be associated with Noonan syndrome, T50I and G60E. Here, we report a mutation in NRAS, resulting in an I24N amino acid substitution, that we identified in an individual bearing typical Noonan syndrome features. The I24N mutation activates N-Ras, resulting in enhanced downstream signaling. Expression of N-Ras-I24N, N-Ras-G60E or the strongly activating mutant N-Ras-G12V, which we included as a positive control, results in developmental defects in zebrafish embryos, demonstrating that these activating N-Ras mutants are sufficient to induce developmental disorders. The defects in zebrafish embryos are reminiscent of symptoms in individuals with Noonan syndrome and phenocopy the defects that other Noonan-syndrome-associated genes induce in zebrafish embryos. MEK inhibition completely rescued the activated N-Ras-induced phenotypes, demonstrating that these defects are mediated exclusively by Ras-MAPK signaling. In conclusion, mutations in NRAS from individuals with Noonan syndrome activated N-Ras signaling and induced developmental defects in zebrafish embryos, indicating that activating mutations in NRAS cause Noonan syndrome.