Noonan syndrome gain-of-function mutations in NRAS cause zebrafish gastrulation defects.
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.
Hubrecht Institute-KNAW and University Medical Center Utrecht, Uppsalalaan 8, 3584 CT Utrecht, The Netherlands.
Vincent
V
Runtuwene
Mark
M
van Eekelen
John
J
Overvoorde
Holger
H
Rehmann
Helger G
HG
Yntema
Willy M
WM
Nillesen
Arie
A
van Haeringen
Ineke
I
van der Burgt
Boudewijn
B
Burgering
Jeroen
J
den Hertog
D019943:Amino Acid Substitution; D000818:Animals; D001483:Base Sequence; D002465:Cell Movement; D019465:Craniofacial Abnormalities / Q000196:embryology / Q000378:metabolism / Q000473:pathology; D004625:Embryo, Nonmammalian / Q000002:abnormalities / Q000378:metabolism / Q000473:pathology; D054262:Gastrulation / Q000235:genetics*; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics*; D009634:Noonan Syndrome / Q000235:genetics*; D015513:Oncogene Proteins / Q000235:genetics* / Q000378:metabolism; D021381:Protein Transport; D015398:Signal Transduction; D015027:Zebrafish / Q000196:embryology* / Q000378:metabolism; D018631:ras Proteins / Q000235:genetics* / Q000378:metabolism
D015513:Oncogene Proteins; D018631:ras Proteins
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