title: Molecular and clinical analysis of RAF1 in Noonan syndrome and related disorders: dephosphorylation of serine 259 as the essential mechanism for mutant activation.
abstract: Noonan syndrome (NS) and related disorders are autosomal dominant disorders characterized by heart defects, facial dysmorphism, ectodermal abnormalities, and mental retardation. The dysregulation of the RAS/MAPK pathway appears to be a common molecular pathogenesis of these disorders: mutations in PTPN11, KRAS, and SOS1 have been identified in patients with NS, those in KRAS, BRAF, MAP2K1, and MAP2K2 in patients with CFC syndrome, and those in HRAS mutations in Costello syndrome patients. Recently, mutations in RAF1 have been also identified in patients with NS and two patients with LEOPARD (multiple lentigines, electrocardiographic conduction abnormalities, ocular hypertelorism, pulmonary stenosis, abnormal genitalia, retardation of growth, and sensorineural deafness) syndrome. In the current study, we identified eight RAF1 mutations in 18 of 119 patients with NS and related conditions without mutations in known genes. We summarized clinical manifestations in patients with RAF1 mutations as well as those in NS patients withPTPN11, SOS1, or KRAS mutations previously reported. Hypertrophic cardiomyopathy and short stature were found to be more frequently observed in patients with RAF1 mutations. Mutations in RAF1 were clustered in the conserved region 2 (CR2) domain, which carries an inhibitory phosphorylation site (serine at position 259; S259). Functional studies revealed that the RAF1 mutants located in the CR2 domain resulted in the decreased phosphorylation of S259, and that mutant RAF1 then dissociated from 14-3-3, leading to a partial ERK activation. Our results suggest that the dephosphorylation of S259 is the primary pathogenic mechanism in the activation of RAF1 mutants located in the CR2 domain as well as of downstream ERK.
authors.affiliation: Department of Medical Genetics, Tohoku University School of Medicine, Sendai, Japan.
authors.forename: Tomoko
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authors.lastname: Kobayashi
authors.forename: Yoko
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authors.forename: Tetsuya
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authors.lastname: Niihori
authors.forename: Hélène
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authors.lastname: Verloes
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authors.lastname: Okamoto
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authors.lastname: Kawame
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authors.lastname: Fujiwara
authors.forename: Fumio
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authors.lastname: Takada
authors.forename: Takako
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authors.lastname: Ohata
authors.forename: Satoru
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authors.lastname: Sakazume
authors.forename: Tatsuya
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authors.lastname: Ando
authors.forename: Noriko
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authors.lastname: Nakagawa
authors.forename: Pablo
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authors.lastname: Lapunzina
authors.forename: Antonio G
authors.initials: AG
authors.lastname: Meneses
authors.forename: Gabriele
authors.initials: G
authors.lastname: Gillessen-Kaesbach
authors.forename: Dagmar
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authors.lastname: Wieczorek
authors.forename: Kenji
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authors.lastname: Kurosawa
authors.forename: Seiji
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authors.lastname: Mizuno
authors.forename: Hirofumi
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authors.lastname: Ohashi
authors.forename: Albert
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authors.lastname: David
authors.forename: Nicole
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authors.lastname: Philip
authors.forename: Afag
authors.initials: A
authors.lastname: Guliyeva
authors.forename: Yoko
authors.initials: Y
authors.lastname: Narumi
authors.forename: Shigeo
authors.initials: S
authors.lastname: Kure
authors.forename: Shigeru
authors.initials: S
authors.lastname: Tsuchiya
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Matsubara
mesh_terms: D048948:14-3-3 Proteins / Q000378:metabolism; D000818:Animals; D009202:Cardiomyopathies / Q000235:genetics; D019066:Facies; D006801:Humans; D051379:Mice; D008957:Models, Genetic; D009154:Mutation; D041681:NIH 3T3 Cells; D009634:Noonan Syndrome / Q000235:genetics*; D010766:Phosphorylation; D011485:Protein Binding; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11 / Q000235:genetics; D019908:Proto-Oncogene Proteins c-raf / Q000235:genetics*; D012694:Serine / Q000235:genetics*
chemical_list: D048948:14-3-3 Proteins; D012694:Serine; D019908:Proto-Oncogene Proteins c-raf; C516724:PTPN11 protein, human; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11