Molecular and Clinical Analysis of RAF1 in Noonan Syndrome and Related Disorders: Dephosphorylation of Serine 259 as the Essential Mechanism for Mutant Activation
Molecular and Clinical Analysis of RAF1 in Noonan Syndrome and Related Disorders: Dephosphorylation of Serine 259 as the Essential Mechanism for Mutant Activation
复制标题
DOI：
10.1002/humu.21187
复制
发表时间：
2010-03-01
期刊：
影响因子：
3.9
通讯作者：
Matsubara, Yoichi
中科院分区：
文献类型：
--
作者：
Kobayashi, Tomoko;Aoki, Yoko;Matsubara, Yoichi
努南综合征(NS)及相关疾病是常染色体显性遗传性疾病，以心脏缺陷、面部畸形、外胚层异常和智力低下为特征。RAS/MAPK通路的失调似乎是这些疾病的常见分子发病机制：已在NS患者中发现PTPN11、KRAS和SOS1突变，在CFC综合征患者中发现KRAS、BRAF、MAP2K1和MAP2K2突变，在Costello综合征患者中发现HRAS突变。最近，在NS患者和两名豹子综合征(多发性扁豆、心电传导异常、眼睛过度调节、肺狭窄、生殖器异常、生长迟缓和感音神经性耳聋)综合征患者中也发现了RAF1基因突变。在目前的研究中，我们在119名NS及相关疾病患者中的18人中发现了8个RAF1突变，这些患者的已知基因没有突变。我们总结了RAF1突变患者以及先前报道的具有PTPN11、SOS I或KRAS突变的NS患者的临床表现。在RAF1基因突变的患者中，肥厚型心肌病和身材矮小更常见。RAF1的突变聚集在保守的第2区(CR2)区域，该区域带有一个抑制性磷酸化位点(259位丝氨酸；S259位)。功能研究表明，位于CR2结构域的RAF1突变体导致S259的磷酸化水平降低，然后RAF1突变体从14-3-3解离，导致ERK部分激活。我们的结果表明，S259的去磷酸化是位于CR2结构域的RAF1突变体激活的主要致病机制，也是ERK下游的致病机制。Hum Mutat 31：284-294,2010。(C)2010年Wiley-Liss公司
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 with PTPN11, SOS I, 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. Hum Mutat 31:284-294, 2010. (C) 2010 Wiley-Liss, Inc.