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Mutations in the Src homology 2 (SH2)-containing protein-tyrosine phosphatase Shp2 (PTPN11) underlie half of the cases of the autosomal dominant genetic disorder Noonan syndrome, and somatic Shp2 mutations are found in several hematologic and solid malignancies. Earlier studies of small numbers of mutants suggested that disease-associated mutations cause constitutive (SH2 binding-independent) activation and that cancer-associated mutants are more active than those associated with Noonan syndrome. We have characterized a larger panel of Shp2 mutants and find that this "activity-centric" model cannot explain the behaviors of all pathogenic Shp2 mutations. Instead, enzymatic, structural, and mathematical modeling analyses show that these mutants can affect basal activation, SH2 domain-phosphopeptide affinity, and/or substrate specificity to varying degrees. Furthermore, there is no absolute correlation between the mutants' extents of basal activation and the diseases they induce. We propose that activated mutants of Shp2 modulate signaling from specific stimuli to a subset of effectors and provide a theoretical framework for understanding the complex relationship between Shp2 activation, intracellular signaling, and pathology.

▪ Abstract Noonan syndrome is a pleiomorphic autosomal dominant disorder with short stature, facial dysmorphia, webbed neck, and heart defects. In the past decade, progress has been made in elucidating the pathogenesis of this disorder using a positional cloning approach. Noonan syndrome is now known to be a genetically heterogeneous disorder with nearly one half of cases caused by gain-of-function mutations in PTPN11, the gene encoding the protein tyrosine phosphatase SHP-2. Similar germ line mutations cause two related genetic disorders, Noonan-like disorder with multiple giant cell lesion syndrome and LEOPARD syndrome, and somatic PTPN11 mutations can underlie certain pediatric hematopoietic malignancies, including juvenile myelomonocytic, acute lymphoblastic, and acute myelogenous leukemias. A mouse model of PTPN11-related Noonan syndrome was recently generated, providing a reagent for studying disease pathogenesis in greater depth as well as experimenting with novel therapeutic strategies.

Medulloblastoma is the commonest brain tumor in childhood and in a minority of patients is associated with an underlying genetic disorder such as Gorlin syndrome or familial adenomatous polyposis. Increased susceptibility to certain tumors, including neuroblastoma and some hematological malignancies, is recognized in disorders caused by mutations in genes encoding components of the RAS signaling pathway which include Noonan syndrome, Noonan syndrome with multiple lentigines (NSML; formerly called LEOPARD syndrome), Costello syndrome, Cardiofaciocutaneous syndrome, Legius syndrome, and Neurofibromatosis type 1 (NF1), collectively termed RASopathies. Although an association between medulloblastoma and NF1 has been reported, this tumor has not previously been reported in other RASopathies. We present a patient with NSML caused by the recurrent PTPN11 mutation c.1403C > T (p.Thr468Met) in whom medulloblastoma was diagnosed at age 10 years. Medulloblastoma could therefore be part of the tumor spectrum associated with this disorder.

Item does not contain fulltext Noonan syndrome (NS) is a developmental disorder characterized by facial dysmorphia, short stature, cardiac defects, and skeletal malformations. We recently demonstrated that mutations in PTPN11, the gene encoding the non-receptor-type protein tyrosine phosphatase SHP-2 (src homology region 2-domain phosphatase-2), cause NS, accounting for approximately 50% of cases of this genetically heterogeneous disorder in a small cohort. All mutations were missense changes and clustered at the interacting portions of the amino-terminal src-homology 2 (N-SH2) and protein tyrosine phosphatase (PTP) domains. A gain of function was postulated as a mechanism for the disease. Here, we report the spectrum and distribution of PTPN11 mutations in a large, well-characterized cohort with NS. Mutations were found in 54 of 119 (45%) unrelated individuals with sporadic or familial NS. There was a significantly higher prevalence of mutations among familial cases than among sporadic ones. All defects were missense, and several were recurrent. The vast majority of mutations altered amino acid residues located in or around the interacting surfaces of the N-SH2 and PTP domains, but defects also affected residues in the C-SH2 domain, as well as in the peptide linking the N-SH2 and C-SH2 domains. Genotype-phenotype analysis revealed that pulmonic stenosis was more prevalent among the group of subjects with NS who had PTPN11 mutations than it was in the group without them (70.6% vs. 46.2%; P

LEOPARD syndrome (multiple Lentigines, Electrocardiographic conduction abnormalities, Ocular hypertelorism, Pulmonary stenosis, Abnormal genitalia, Retardation of growth, sensorineural Deafness; LS), also called Noonan syndrome with multiple lentigines (NSML), is a rare autosomal dominant disorder associating various developmental defects, notably cardiopathies, dysmorphism, and short stature. It is mainly caused by mutations of the PTPN11 gene that catalytically inactivate the tyrosine phosphatase SHP2 (Src-homology 2 domain-containing phosphatase 2). Besides its pleiotropic roles during development, SHP2 plays key functions in energetic metabolism regulation. However, the metabolic outcomes of LS mutations have never been examined. Therefore, we performed an extensive metabolic exploration of an original LS mouse model, expressing the T468M mutation of SHP2, frequently borne by LS patients. Our results reveal that, besides expected symptoms, LS animals display a strong reduction of adiposity and resistance to diet-induced obesity, associated with overall better metabolic profile. We provide evidence that LS mutant expression impairs adipogenesis, triggers energy expenditure, and enhances insulin signaling, three features that can contribute to the lean phenotype of LS mice. Interestingly, chronic treatment of LS mice with low doses of MEK inhibitor, but not rapamycin, resulted in weight and adiposity gains. Importantly, preliminary data in a French cohort of LS patients suggests that most of them have lower-than-average body mass index, associated, for tested patients, with reduced adiposity. Altogether, these findings unravel previously unidentified characteristics for LS, which could represent a metabolic benefit for patients, but may also participate to the development or worsening of some traits of the disease. Beyond LS, they also highlight a protective role of SHP2 global LS-mimicking modulation toward the development of obesity and associated disorders.

Noonan syndrome with multiple lentigines (NSML) is primarily caused by mutations in the nonreceptor protein tyrosine phosphatase SHP2 and associated with congenital heart disease in the form of pulmonary valve stenosis and hypertrophic cardiomyopathy (HCM). Our goal was to elucidate the cellular mechanisms underlying the development of HCM caused by the Q510E mutation in SHP2. NSML patients carrying this mutation suffer from a particularly severe form of HCM. Drawing parallels to other, more common forms of HCM, we hypothesized that altered Ca2+ homeostasis and/or sarcomeric mechanical properties play key roles in the pathomechanism. We used transgenic mice with cardiomyocyte-specific expression of Q510E-SHP2 starting before birth. Mice develop neonatal onset HCM with increased ejection fraction and fractional shortening at 4–6 wk of age. To assess Ca2+ handling, isolated cardiomyocytes were loaded with fluo-4. Q510E-SHP2 expression increased Ca2+ transient amplitudes during excitation-contraction coupling and increased sarcoplasmic reticulum Ca2+ content concurrent with increased expression of sarco(endo)plasmic reticulum Ca2+-ATPase. In skinned cardiomyocyte preparations from Q510E-SHP2 mice, force-velocity relationships and power-load curves were shifted upward. The peak power-generating capacity was increased approximately twofold. Transmission electron microscopy revealed that the relative intracellular area occupied by sarcomeres was increased in Q510E-SHP2 cardiomyocytes. Triton X-100-based myofiber purification showed that Q510E-SHP2 increased the amount of sarcomeric proteins assembled into myofibers. In summary, Q510E-SHP2 expression leads to enhanced contractile performance early in disease progression by augmenting intracellular Ca2+ cycling and increasing the number of power-generating sarcomeres. This gives important new insights into the cellular pathomechanisms of Q510E-SHP2-associated HCM.

The RASopathies are a relatively common group of phenotypically similar and genetically related autosomal dominant genetic syndromes caused by missense mutations affecting genes participating in the RAS/mitogen-activated protein kinase (MAPK) pathway that include Noonan syndrome (NS) and Noonan syndrome with multiple lentigines (NSML, formerly LEOPARD syndrome). NS and NSML can be difficult to differentiate during infancy, but the presence of multiple lentigines, cafe au lait spots, and specific cardiac defects facilitate the diagnosis. Furthermore, individual PTPN11 missense mutations are highly specific to each syndrome and engender opposite biochemical alterations on the function of SHP-2, the protein product of that gene. Here, we report on a 5-year-old male with two de novo PTPN11 mutations in cis, c.1471C>T (p.Pro491Ser), and c.1492C>T (p.Arg498Trp), which are associated with NS and NSML, respectively. This boy's phenotype is intermediate between NS and NSML with facial dysmorphism, short stature, mild global developmental delay, pulmonic stenosis, and deafness but absence of cafe au lait spots or lentigines. The double-mutant SHP-2 was found to be catalytically impaired. This raises the question of whether clinical differences between NS and NSML can be ascribed solely to the relative SHP-2 catalytic activity.

The term RASopathies designates a group of developmental syndromes caused by germline mutations in genes that encode proteins of the Ras/mitogen-activated protein kinase (MAPK) signalling pathway. Ras/MAPK pathway controls several biological functions, such as cell proliferation, migration, differentiation and apoptosis. Similar molecular mechanisms disturbing the Ras/MAPK pathway were described in the RASopathies, including Noonan syndrome, Noonan syndrome with multiple lentigines, Noonan syndrome-like disorder with loose anagen hair, CBL mutation-associated syndrome, Costello syndrome, cardiofaciocutaneous syndrome, neurofibromatosis type 1 and Legius syndrome. Even though these syndromes share some overlapping features, genotype–phenotype correlations are well established for each of these, supporting the idea that they represent clinically distinct disorders. Owing to the similar mechanism encompassing Ras/MAPK germline and somatic mutations, Ras/MAPK pathway components have been considered a potential therapeutic target for RASopathies by promoting pathway modulation or small-molecule inhibition. Key Concepts: Ras/MAPK is one of the most well-known signalling pathways and plays an important role in critical cellular functions to normal development. RASopathies are a group of medical genetic disorders caused by gain-of-function germline mutations in components of the Ras/MAPK signalling pathway. Although the RASopathies may share clinically overlapping features, they also exhibit some individual ones that support the concept that they are distinct disorders. Ras/MAPK germline mutations are similar to somatic mutations when associated with cancer, but they tend to be weakly activating. Noonan syndrome is a frequent autosomal dominant disorder characterised by facial dysmorphisms, heart defects, short stature and learning disabilities. The best clinical practice for each RASopathy could be defined if its genotype–phenotype correlation is understood. Keywords: cardiofaciocutaneous syndrome; Costello syndrome; Legius syndrome; LEOPARD syndrome; neurofibromatosis; Noonan syndrome; Ras/MAPK; RASopathies; signal transduction pathway

Noonan syndrome, a developmental disorder characterized by congenital heart defects, reduced growth, facial dysmorphism and variable cognitive deficits, is caused by constitutional dysregulation of the RAS-MAPK signaling pathway. Here we report that germline NRAS mutations conferring enhanced stimulus-dependent MAPK activation account for some cases of this disorder. These findings provide evidence for an obligate dependency on proper NRAS function in human development and growth.

The RAS/MAPK pathway proteins with germline mutations in their respective genes are associated with some disorders such as Noonan, LEOPARD (LS), neurofibromatosis type 1, Costello and cardio-facio-cutaneous syndromes. LEOPARD is an acronym, mnemonic for the major manifestations of this disorder, characterized by multiple lentigines, electrocardiographic abnormalities, ocular hypertelorism, pulmonic stenosis, abnormal genitalia, retardation of growth, and sensorineural deafness. Though it is not included in the acronym, hypertrophic cardiomyopathy is the most frequent cardiac anomaly observed, representing a potentially life-threatening problem in these patients. PTPN11, RAF1 and BRAF are the genes known to be associated with LS, identifying molecular genetic testing of the 3 gene mutations in about 95% of affected individuals. PTPN11 mutations are the most frequently found. Eleven different missense PTPN11 mutations (Tyr279Cys/Ser, Ala461Thr, Gly464Ala, Thr468Met/Pro, Arg498Trp/Leu, Gln506Pro, and Gln510Glu/Pro) have been reported so far in LS, 2 of which (Tyr279Cys and Thr468Met) occur in about 65% of the cases. Here, we provide an overview of clinical aspects of this disorder, the molecular mechanisms underlying pathogenesis and major genotype-phenotype correlations.

Noonan syndrome (NS) is a clinically variable and genetically heterogeneous disorder with congenital heart defects (CHD), short stature, and craniofacial dysmorphisms. Gain-of-function mutations in RAF1 can cause NS and the highly related NS with multiple lentigines (previously known as LEOPARD syndrome). Here we report on a 15-year-old male with NS phenotype: short stature, heart defects, low posterior hairline, facial malformations, malformed left ear with sensorineural hearing loss, widely spaced nipples, and unilateral upper limb anomaly. Using high-resolution SNP array technology, we identified in this patient a 0.25 Mb microduplication at 3p25.2 in which RAF1 is located. Sequence analysis did not identify mutations in genes associated with Holt-Oram syndrome. These findings suggest that duplications of genomic regions encompassing RAF1 could cause NS and are consistent with the notion that rare copy number variations encompassing causative genes may underlie a small percentage of patients with syndromic CHD like NS. © 2012 Wiley Periodicals, Inc.

Noonan syndrome (NS) and Noonan-related disorders [cardio-facio-cutaneous (CFC), Costello, Noonan syndrome with multiple lentigines (NS-ML), and neurofibromatosis-Noonan syndromes (NFNS)] are a group of developmental disorders caused by mutations in genes of the RAS/MAPK pathway. Mutations in the KRAS gene account for only a small proportion of affected Noonan and CFC syndrome patients that present an intermediate phenotype between these two syndromes, with more frequent and severe intellectual disability in NS and less ectodermal involvement in CFC syndrome, as well as atypical clinical findings such as craniosynostosis. Recently, the first familial case with a novel KRAS mutation was described. We report on a second vertical transmission (a mother and two siblings) with a novel mutation (p.M72L), in which the proband has trigonocephaly and the affected mother and sister, prominent ectodermal involvement. Metopic suture involvement has not been described before, expanding the main different cranial sutures which can be affected in NS and KRAS gene mutations. The gene alteration found in the studied family is in close proximity to the one reported in the other familial case (close to the switch II region of the G-domain), suggesting that this specific region of the gene could have less severe effects on intellectual ability than the other KRAS gene mutations found in NS patients and be less likely to hamper reproductive fitness.

Noonan syndrome is a relatively common, clinically variable developmental disorder. Cardinal features include postnatally reduced growth, distinctive facial dysmorphism, congenital heart defects and hypertrophic cardiomyopathy, variable cognitive deficit and skeletal, ectodermal and hematologic anomalies. Noonan syndrome is transmitted as an autosomal dominant trait, and is genetically heterogeneous. So far, heterozygous mutations in nine genes (PTPN11, SOS1, KRAS, NRAS, RAF1, BRAF, SHOC2, MEK1 and CBL) have been documented to underlie this disorder or clinically related phenotypes. Based on these recent discoveries, the diagnosis can now be confirmed molecularly in approximately 75% of affected individuals. Affected genes encode for proteins participating in the RAS-mitogen-activated protein kinases (MAPK) signal transduction pathway, which is implicated in several developmental processes controlling morphology determination, organogenesis, synaptic plasticity and growth. Here, we provide an overview of clinical aspects of this disorder and closely related conditions, the molecular mechanisms underlying pathogenesis, and major genotype-phenotype correlations.

Noonan syndrome (NS), Costello syndrome (CS), cardiofaciocutaneous syndrome (CFCS), and LEOPARD syndrome (now also referred to as Noonan syndrome with multiple lentigines or NSML) are clinically overlapping dominant disorders that are caused by mutations in RAS signaling pathway genes. The spectrum of cancer susceptibility in this group of disorders has not been studied in detail. We identified more than 1900 cases of NS, CS, CFCS, or NSML reported in the literature between 1937 to 2010; eighty-eight cancers were reported. The most common cancers reported in 1051 NS subjects were neuroblastoma (n=8), acute lymphoblastic leukemia (n=8), low grade glioma (n=6), and rhabdomyosarcoma (n=6). These associations are biologically plausible, given that somatic RAS pathway mutations are known to occur in these specific cancers. In addition, 40 childhood cases of myeloproliferative disease were described in individuals with NS, several of whom experienced a benign course of this hematologic condition. We confirmed the previously-described association between CS and cancer in 268 reported individuals: 19 had rhabdomyosarcoma, 4 had bladder cancer, and 5 had neuroblastoma. By age 20, the cumulative incidence of cancer was approximately 4% for NS and 15% for CS; both syndromes had a cancer incidence peak in childhood. The cancers described in CFCS and NSML overlapped with those reported in NS and CS. Future epidemiologic studies will be required to confirm the described cancer spectrum and to estimate precise cancer risks.

N-myristoylation is a common form of co-translational protein fatty acylation resulting from the attachment of myristate to a required N-terminal glycine residue(1,2). We show that aberrantly acquired N-myristoylation of SHOC2, a leucine-rich repeat-containing protein that positively modulates RAS-MAPK signal flow(3-6), underlies a clinically distinctive condition of the neuro-cardio-facial-cutaneous disorders family. Twenty-five subjects with a relatively consistent phenotype previously termed Noonan-like syndrome with loose anagen hair (MIM607721)(7) shared the 4A>G missense change in SHOC2 (producing an S2G amino acid substitution) that introduces an N-myristoylation site, resulting in aberrant targeting of SHOC2 to the plasma membrane and impaired translocation to the nucleus upon growth factor stimulation. Expression of SHOC2(S2G) in vitro enhanced MAPK activation in a cell typespecific fashion. Induction of SHOC2(S2G) in Caenorhabditis elegans engendered protruding vulva, a neomorphic phenotype previously associated with aberrant signaling. These results document the first example of an acquired N-terminal lipid modification of a protein causing human disease.

LEOPARD syndrome (LS, OMIM 151100) is a rare multiple congenital anomalies condition, mainly characterized by skin, facial and cardiac anomalies. LEOPARD is an acronym for the major features of this disorder, including multiple Lentigines, ECG conduction abnormalities, Ocular hypertelorism, Pulmonic stenosis, Abnormal genitalia, Retardation of growth, and sensorineural Deafness. About 200 patients have been reported worldwide but the real incidence of LS has not been assessed. Facial dysmorphism includes ocular hypertelorism, palpebral ptosis and low-set ears. Stature is usually below the 25th centile. Cardiac defects, in particular hypertrophic cardiomyopathy mostly involving the left ventricle, and ECG anomalies are common. The lentigines may be congenital, although more frequently manifest by the age of 4–5 years and increase throughout puberty. Additional common features are café-au-lait spots (CLS), chest anomalies, cryptorchidism, delayed puberty, hypotonia, mild developmental delay, sensorineural deafness and learning difficulties. In about 85% of the cases, a heterozygous missense mutation is detected in exons 7, 12 or 13 of the PTPN11 gene. Recently, missense mutations in the RAF1 gene have been found in two out of six PTPN11-negative LS patients. Mutation analysis can be carried out on blood, chorionic villi and amniotic fluid samples. LS is largely overlapping Noonan syndrome and, during childhood, Neurofibromatosis type 1-Noonan syndrome. Diagnostic clues of LS are multiple lentigines and CLS, hypertrophic cardiomyopathy and deafness. Mutation-based differential diagnosis in patients with borderline clinical manifestations is warranted. LS is an autosomal dominant condition, with full penetrance and variable expressivity. If one parent is affected, a 50% recurrence risk is appropriate. LS should be suspected in foetuses with severe cardiac hypertrophy and prenatal DNA test may be performed. Clinical management should address growth and motor development and congenital anomalies, in particular cardiac defects that should be monitored annually. Hypertrophic cardiomyopathy needs careful risk assessment and prophylaxis against sudden death in patients at risk. Hearing should be evaluated annually until adulthood. With the only exception of ventricular hypertrophy, adults with LS do not require special medical care and long-term prognosis is favourable.

The RAS proteins and their downstream pathways play pivotal roles in cell proliferation, differentiation, survival and cell death, but their physiological roles in human development had remained unknown. Noonan syndrome, Costello syndrome, and cardio-facio-cutaneous (CFC) syndrome are autosomal dominant multiple congenital anomaly syndromes characterized by a distinctive facial appearance, heart defects, musculocutaneous abnormalities, and mental retardation. A variety of mutations in protein tyrosine phosphatase, non-receptor type 11(PTPN11) has been identified in 50% of Noonan patients. Specific mutations in PTPN11 have been identified in LEOPARD (multiple lentigines, electrocardiographic conduction abnormalities, ocular hypertelorism, pulmonary stenosis, abnormal genitalia, retardation of growth, and sensorineural deafness) syndrome. In 2005, we discovered Harvey-RAS (HRAS) germline mutations in patients with Costello syndrome. This discovery provided a clue to identification of germline mutations in Kirsten-RAS (KRAS), BRAF and mitogen-activated protein kinase kinase 1 and 2 (MAP2K1/MAP2K2) in patients with CFC syndrome. These genes encode molecules in the RAS/RAF/MEK/extracellular signal-regulated kinase (ERK) pathway, leading to a new concept that clinically related disorders, i.e., Noonan, Costello, and CFC syndromes are caused by dysregulation of the RAS/mitogen activated protein kinase (MAPK) pathway. In the present review, we summarize mutations in HRAS, KRAS, BRAF, MAP2K1/2, and PTPN11, the phenotypes of patients with these mutations, the functional properties of mutants and animal models. Finally we suggest that disorders with mutations of molecules in the RAS/MAPK cascade (Noonan, LEOPARD, Costello, and CFC syndromes and neurofibromatosis type I) may be comprehensively termed "the RAS/MAPK syndromes." Details on mutations will be updated in the RAS/MAPK Syndromes Homepage (www.medgen.med.tohoku.ac.jp/RasMapk syndromes.html).

Ras genes are the most common targets for somatic gain-of-function mutations in human cancer. Recently, germline mutations that affect components of the Ras-Raf- mitogen-activated and extracellular-signal regulated kinase kinase (MEK)-extracellular signal-regulated kinase (ERK) pathway were shown to cause several developmental disorders, including Noonan, Costello and cardio-facio-cutaneous syndromes. Many of these mutant alleles encode proteins with aberrant biochemical and functional properties. Here we will discuss the implications of germline mutations in the Ras-Raf-MEK-ERK pathway for understanding normal developmental processes and cancer pathogenesis.

Noonan syndrome is characterized by short stature, facial dysmorphia and a wide spectrum of congenital heart defects1,2. Mutations of PTPN11, KRAS and SOS1 in the RAS-MAPK pathway cause ∼60% of cases of Noonan syndrome3,4,5,6,7,8,9. However, the gene(s) responsible for the remainder are unknown. We have identified five different mutations in RAF1 in ten individuals with Noonan syndrome; those with any of four mutations causing changes in the CR2 domain of RAF1 had hypertrophic cardiomyopathy (HCM), whereas affected individuals with mutations leading to changes in the CR3 domain did not. Cells transfected with constructs containing Noonan syndrome–associated RAF1 mutations showed increased in vitro kinase and ERK activation, and zebrafish embryos with morpholino knockdown of raf1 demonstrated the need for raf1 for the development of normal myocardial structure and function. Thus, our findings implicate RAF1 gain-of-function mutations as a causative agent of a human developmental disorder, representing a new genetic mechanism for the activation of the MAPK pathway.

Noonan and LEOPARD syndromes are developmental disorders with overlapping features, including cardiac abnormalities, short stature and facial dysmorphia. Increased RAS signaling owing to PTPN11, SOS1 and KRAS mutations causes approximately 60% of Noonan syndrome cases, and PTPN11 mutations cause 90% of LEOPARD syndrome cases. Here, we report that 18 of 231 individuals with Noonan syndrome without known mutations (corresponding to 3% of all affected individuals) and two of six individuals with LEOPARD syndrome without PTPN11 mutations have missense mutations in RAF1, which encodes a serine-threonine kinase that activates MEK1 and MEK2. Most mutations altered a motif flanking Ser259, a residue critical for autoinhibition of RAF1 through 14-3-3 binding. Of 19 subjects with a RAF1 mutation in two hotspots, 18 (or 95%) showed hypertrophic cardiomyopathy (HCM), compared with the 18% prevalence of HCM among individuals with Noonan syndrome in general. Ectopically expressed RAF1 mutants from the two HCM hotspots had increased kinase activity and enhanced ERK activation, whereas non-HCM-associated mutants were kinase impaired. Our findings further implicate increased RAS signaling in pathological cardiomyocyte hypertrophy.

Noonan syndrome is a developmental disorder characterized by short stature, facial dysmorphia, congenital heart defects and skeletal anomalies. Increased RAS-mitogen-activated protein kinase (MAPK) signaling due to PTPN11 and KRAS mutations causes 50% of cases of Noonan syndrome. Here, we report that 22 of 129 individuals with Noonan syndrome without PTPN11 or KRAS mutation have missense mutations in SOS1, which encodes a RAS-specific guanine nucleotide exchange factor. SOS1 mutations cluster at codons encoding residues implicated in the maintenance of SOS1 in its autoinhibited form. In addition, ectopic expression of two Noonan syndrome-associated mutants induces enhanced RAS and ERK activation. The phenotype associated with SOS1 defects lies within the Noonan syndrome spectrum but is distinctive, with a high prevalence of ectodermal abnormalities but generally normal development and linear growth. Our findings implicate gain-of-function mutations in a RAS guanine nucleotide exchange factor in disease for the first time and define a new mechanism by which upregulation of the RAS pathway can profoundly change human development.

Contains fulltext : 50085.pdf (Publisher’s version ) (Closed access) Noonan syndrome (MIM 163950) is characterized by short stature, facial dysmorphism and cardiac defects. Heterozygous mutations in PTPN11, which encodes SHP-2, cause approximately 50% of cases of Noonan syndrome. The SHP-2 phosphatase relays signals from activated receptor complexes to downstream effectors, including Ras. We discovered de novo germline KRAS mutations that introduce V14I, T58I or D153V amino acid substitutions in five individuals with Noonan syndrome and a P34R alteration in a individual with cardio-facio-cutaneous syndrome (MIM 115150), which has overlapping features with Noonan syndrome. Recombinant V14I and T58I K-Ras proteins show defective intrinsic GTP hydrolysis and impaired responsiveness to GTPase activating proteins, render primary hematopoietic progenitors hypersensitive to growth factors and deregulate signal transduction in a cell lineage-specific manner. These studies establish germline KRAS mutations as a cause of human disease and infer that the constellation of developmental abnormalities seen in Noonan syndrome spectrum is, in large part, due to hyperactive Ras.

LEOPARD syndrome (LS) is an autosomal dominant syndrome characterized by multiple lentigines and café-au-lait spots, electrocardiographic-conduction abnormalities, ocular hypertelorism/obstructive cardiomyopathy, pulmonary stenosis, abnormalities of the genitalia in males, retardation of growth, and deafness. LS shares many features with Noonan syndrome (NS), in which lentigines and deafness are usually not present. Molecular studies have shown that LS and NS are allelic disorders, caused by different missense mutations in PTPN11, a gene encoding the protein tyrosine phosphatase SHP-2 located at chromosome 12q22-qter. The clinical diagnosis of LS is generally difficult in the first months of life because the distinctive lentigines are generally not present at birth and develop during childhood. From January 2002 to December 2004, we suspected LS clinically in 10 patients admitted to our genetic counseling services in the first 12 months of life. A PTPN11 gene mutation was detected in 8/10 (80%) patients. In one patient without a PTPN11 mutation a subsequent clinical diagnosis of neurofibromatosis type 1 (NF1) was made, following the evaluation of the mother, who had previously undiagnosed classic NF1. The age of LS patients with PTPN11 mutation ranged between 1 and 11 months (mean age +/- SD 7.5 +/- 3.96 months). Review of the clinical characteristics of patients with LS confirmed by molecular study during the first year of life demonstrates that the diagnosis of LS in the first months of age can be clinically suspected in patients presenting with three main features, that is, characteristic facial features (100%), hypertrophic cardiomyopathy (HCM) (87%), and cafe-au-lait spots (75%). Characteristic facial features can be mild or severe, and consist of hypertelorism, downslanting palpebral fissures, ptosis, and dysmorphic ears. The clinical suspicion of LS may be confirmed by molecular screening for PTPN11 mutations. An early diagnosis of the disease is useful for the prospective care of associated medical problems and for precise genetic counseling.

Cardio-facio-cutaneous (CFC) syndrome is characterized by a distinctive facial appearance, heart defects and mental retardation. It phenotypically overlaps with Noonan and Costello syndrome, which are caused by mutations in PTPN11 and HRAS, respectively. In 43 individuals with CFC, we identified two heterozygous KRAS mutations in three individuals and eight BRAF mutations in 16 individuals, suggesting that dysregulation of the RAS-RAF-ERK pathway is a common molecular basis for the three related disorders.

Costello syndrome is a multiple congenital anomaly and mental retardation syndrome characterized by coarse face, loose skin, cardiomyopathy and predisposition to tumors. We identified four heterozygous de novo mutations of HRAS in 12 of 13 affected individuals, all of which were previously reported as somatic and oncogenic mutations in various tumors. Our observations suggest that germline mutations in HRAS perturb human development and increase susceptibility to tumors.

Noonan syndrome is a common human autosomal dominant birth defect, characterized by short stature, facial abnormalities, heart defects and possibly increased risk of leukemia. Mutations of Ptpn11 (also known as Shp2), which encodes the protein-tyrosine phosphatase Shp2, occur in approximately 50% of individuals with Noonan syndrome, but their molecular, cellular and developmental effects, and the relationship between Noonan syndrome and leukemia, are unclear. We generated mice expressing the Noonan syndrome-associated mutant D61G. When homozygous, the D61G mutant is embryonic lethal, whereas heterozygotes have decreased viability. Surviving Ptpn11(D61G/+) embryos ( approximately 50%) have short stature, craniofacial abnormalities similar to those in Noonan syndrome, and myeloproliferative disease. Severely affected Ptpn11(D61G/+) embryos ( approximately 50%) have multiple cardiac defects similar to those in mice lacking the Ras-GAP protein neurofibromin. Their endocardial cushions have increased Erk activation, but Erk hyperactivation is cell and pathway specific. Our results clarify the relationship between Noonan syndrome and leukemia and show that a single Ptpn11 gain-of-function mutation evokes all major features of Noonan syndrome by acting on multiple developmental lineages in a gene dosage-dependent and pathway-selective manner.

Src homology-2 (SH2) domain-containing phosphatases (Shps) are a small, highly conserved subfamily of protein-tyrosine phosphatases, members of which are present in both vertebrates and invertebrates. The mechanism of regulation of Shps by ligand binding is now well understood. Much is also known about the normal signaling pathways regulated by each Shp and the consequences of Shp deficiency. Recent studies have identified mutations in human Shp2 as the cause of the inherited disorder Noonan syndrome. Shp2 mutations might also contribute to the pathogenesis of some leukemias. In addition, Shp2 might be a key virulence determinant for the important human pathogen Helicobacter pylori. Despite these efforts, however, the key targets of each Shp have remained elusive. Identifying these substrates remains a major challenge for future research.

LEOPARD syndrome is an autosomal dominant disorder with multiple lentigines, congenital cardiac abnormalities, ocular hypertelorism, and retardation of growth. Deafness and genital abnormalities are less frequently found. We report a father and daughter and a third, unrelated patient with LEOPARD syndrome. Recently, missense mutations in the PTPN11 gene located in 12q24 were found to cause Noonan syndrome. All three cases of LEOPARD syndrome reported here have a Y279C mutation in the PTPN11 gene. We hypothesise that some PTPN11 mutations are associated with the typical Noonan syndrome phenotype and that other mutations, such as the Y279C mutation reported here, are associated with both the Noonan syndrome phenotype and with skin pigmentation anomalies, such as multiple lentigines or cafe au lait spots.

Multiple-lentigines (ML)/LEOPARD (multiple lentigines, electrocardiographic-conduction abnormalities, ocular hypertelorism, pulmonary stenosis, abnormal genitalia, retardation of growth, and sensorineural deafness) syndrome is an autosomal dominant condition—characterized by lentigines and café au lait spots, facial anomalies, cardiac defects—that shares several clinical features with Noonan syndrome (NS). We screened nine patients with ML/LEOPARD syndrome (including a mother-daughter pair) and two children with NS who had multiple café au lait spots, for mutations in the NS gene, PTPN11, and found, in 10 of 11 patients, one of two new missense mutations, in exon 7 or exon 12. Both mutations affect the PTPN11 phosphotyrosine phosphatase domain, which is involved in

Item does not contain fulltext Noonan syndrome (MIM 163950) is an autosomal dominant disorder characterized by dysmorphic facial features, proportionate short stature and heart disease (most commonly pulmonic stenosis and hypertrophic cardiomyopathy). Webbed neck, chest deformity, cryptorchidism, mental retardation and bleeding diatheses also are frequently associated with this disease. This syndrome is relatively common, with an estimated incidence of 1 in 1,000-2,500 live births. It has been mapped to a 5-cM region (NS1) [corrected] on chromosome 12q24.1, and genetic heterogeneity has also been documented. Here we show that missense mutations in PTPN11 (MIM 176876)-a gene encoding the nonreceptor protein tyrosine phosphatase SHP-2, which contains two Src homology 2 (SH2) domains-cause Noonan syndrome and account for more than 50% of the cases that we examined. All PTPN11 missense mutations cluster in interacting portions of the amino N-SH2 domain and the phosphotyrosine phosphatase domains, which are involved in switching the protein between its inactive and active conformations. An energetics-based structural analysis of two N-SH2 mutants indicates that in these mutants there may be a significant shift of the equilibrium favoring the active conformation. This implies that they are gain-of-function changes and that the pathogenesis of Noonan syndrome arises from excessive SHP-2 activity.

The multiple lentigines syndrome is reviewed and a new case is presented. The major features of this syndrome are lentigines and other cutaneous abnormalities, cardiac defects, meurologic defects, cephalofacila dysmorphism, shortness of stature, skeletal anomalies, genitourinary abnormalities, and a family history consistent with an autosomal dominant mode of inheritance. The multiple lentigines syndrome manifests markedly variable expressivity; no single finding is pathognomonic and few patients have all major features. We propose specific criteria for diagnosis.

RAS GTPases mediate a wide variety of cellular functions, including cell proliferation, survival, and differentiation. Recent studies have revealed that germline mutations and mosaicism for classical RAS mutations, including those in HRAS, KRAS, and NRAS, cause a wide spectrum of genetic disorders. These include Noonan syndrome and related disorders (RAS/mitogen-activated protein kinase [RAS/MAPK] pathway syndromes, or RASopathies), nevus sebaceous, and Schimmelpenning syndrome. In the present study, we identified a total of nine missense, nonsynonymous mutations in RIT1, encoding a member of the RAS subfamily, in 17 of 180 individuals (9%) with Noonan syndrome or a related condition but with no detectable mutations in known Noonan-related genes. Clinical manifestations in the RIT1-mutation-positive individuals are consistent with those of Noonan syndrome, which is characterized by distinctive facial features, short stature, and congenital heart defects. Seventy percent of mutation-positive individuals presented with hypertrophic cardiomyopathy; this frequency is high relative to the overall 20% incidence in individuals with Noonan syndrome. Luciferase assays in NIH 3T3 cells showed that five RIT1 alterations identified in children with Noonan syndrome enhanced ELK1 transactivation. The introduction of mRNAs of mutant RIT1 into 1-cell-stage zebrafish embryos was found to result in a significant increase of embryos with craniofacial abnormalities, incomplete looping, a hypoplastic chamber in the heart, and an elongated yolk sac. These results demonstrate that gain-of-function mutations in RIT1 cause Noonan syndrome and show a similar biological effect to mutations in other RASopathy-related genes.

Noonan syndrome (MIM 163950), an autosomal dominant disorder with an estimated prevalence of 1/1000–2500 at birth, is characterised by short stature, facial anomalies, pterygium colli, and congenital heart disease.1,2 Although pulmonary valve stenosis with dysplastic leaflets, hypertrophic cardiomyopathy, and atrial septal defects (ASD) are the most common congenital heart defects in Noonan syndrome,3 a broad spectrum of cardiac phenotypes has been recognised.2–6 About half the affected individuals have PTPN11 gene mutations.7–9 This gene, which maps to chromosome 12q22-qter,10 encodes for the human SH2 domain containing protein tyrosine phosphatase (SHP2).11 PTPN11 gene mutations have also been detected in multiple lentigines/LEOPARD syndrome (multiple lentigines, ECG conduction abnormalities, ocular hypertelorism, pulmonary stenosis, abnormal genitalia, retardation of growth and sensorineural deafness; ML/LS, MIM 151100),12,13 in Noonan-like/multiple giant cell lesion syndrome (MIM 163955),8 in two families presumably affected by cardio-facio-cutaneous syndrome (CFCS, MIM 115150),14 but not in sporadic CFCS.15 The clinical and genetic heterogeneity of these disorders suggests a possible relation between different PTPN11 gene mutations and distinct clinical features. A genotype–phenotype correlation study in Noonan syndrome found an association between pulmonary stenosis and PTPN11 mutations.8 Our aim in this study was to screen a large cohort of patients with Noonan syndrome and ML/LS in order to expand the genotype–phenotype correlation analysis, with particular emphasis on cardiac diseases. ### Key points

Congenital melanocytic naevi (CMN) are moles that are present from birth. These can be isolated cutaneous lesions, single or multiple (defined as two or more CMN at birth), or when multiple can be associated with extracutaneous abnormalities, then termed CMN syndrome. Extracutaneous associations described thus far are characteristic facial features,1 and a wide range of neurological abnormalities detectable on magnetic resonance imaging (MRI),2, 3 seen in approximately 20% of children with more than one CMN at birth.4 Molecular studies have established that approximately 80% of cases of multiple CMN or CMN syndrome are caused by mosaicism for oncogenic mutations in codon 61 of NRAS,5 classifying the majority as a mosaic RASopathy. Primary melanoma can arise within the skin or central nervous system (CNS), more commonly in those with a severe cutaneous phenotype,6 and this malignant complication is associated with further genetic events.5 Many RASopathies manifest abnormalities of pre‐ or postnatal growth, or of endocrine dysfunction. For example, neurofibromatosis type 1 is characterized by macrocephaly,7 early puberty and growth failure,8 and Costello syndrome babies have a higher than average birthweight9 often with hypoglycaemia.10 Moreover, cardio–facio–cutaneous syndrome, Noonan syndrome and Noonan syndrome with multiple lentigines are associated with postnatal short stature, and complex subtle endocrine abnormalities are seen frequently in Noonan syndrome.11, 12 The molecular mechanisms behind such variation in growth and endocrine abnormalities in the RASopathies is not understood; however, the MAPK pathway is known to be involved in metabolic signalling.13 Several clinical observations directed our attention to metabolic and endocrine function in children with CMN (Fig. ​(Fig.1):1): firstly, the clinically well‐recognized decrease in bulk of subcutaneous tissues under large CMN, hitherto thought to be fat atrophy but never formally studied; secondly, the previously undescribed presentation of premature thelarche variant in a series of young girls with CMN; thirdly, the occurrence of undescended testes in some babies with bathing trunk naevi (i.e. affecting the genital area). Figure 1 Clinical images of children with multiple congenital melanocytic naevi showing (a–c) lack of bulk of underlying tissues associated with overlying naevus: (a) decreased girth but not length of left leg; (b) lower abdomen; (c) decreased girth but ... Premature thelarche variant (sometimes termed exaggerated thelarche) is a relatively rare subset of premature secondary sexual development that shares features with both isolated premature thelarche and precocious puberty.14 It is characterized biochemically by the dominance of serum concentrations of follicle‐stimulating hormone (FSH) over luteinizing hormone (LH), and clinically by a slight acceleration in growth, the appearance of sparse pubic hair together with breast development, and/or minor increases in uterine measurements,15 in the presence of a normal MRI of the CNS. It does not affect final height, unlike true precocious puberty. Growth and hormone status have not previously been investigated in individuals with CMN. We recruited a cohort of subjects with CMN for prospective endocrinological assessment, and used a larger group of patients with CMN from outpatient clinics (which included all subjects in the endocrinological assessment group) for a retrospective review of longitudinal growth.

Multiple lentigines LEOPARD syndrome (MIM 151100) is an autosomal dominant multiple congenital anomaly syndrome, with high penetrance and markedly variable expression.1 The acronym LEOPARD was coined by Gorlin et al. in 1971 as a mnemonic of the major features of this disorder: multiple l entigines, E CG conduction abnormalities, o cular hypertelorism, p ulmonic stenosis, a bnormal genitalia, r etardation of growth, and sensorineural d eafness.2 It is also known as cardiocutaneous syndrome, Moynahan syndrome, lentiginosis profuse, and progressive cardiomyopathic lentiginosis.3,4 Voron et al. proposed some diagnostic criteria for multiple lentigines LEOPARD syndrome.5 More than 100 cases have been described, and one review has been published.5,6 Multiple lentigines LEOPARD syndrome shares many features with Noonan syndrome (MIM 163950),7–9 in which lentigines and deafness usually are not present. About 40% of patients with Noonan syndrome have missense mutations in the PTPN11 gene, which encodes for the protein tyrosine phosphatase SHP2.10–14 Multiple lentigines LEOPARD syndrome has proved to be allelic to Noonan syndrome,15,16 with two recurrent PTPN11 mutations in exons 7 (Tyr279Cys) and 12 (Thr468Met). Recently, we reported a novel PTPN11 mutation (Gln506Pro) in a unique patient with multiple lentigines LEOPARD syndrome, which suggests that mutations other than Tyr279Cys and Thr468Met could be found in these patients.17 As PTPN11 mutations in multiple lentigines LEOPARD syndrome and Noonan syndrome are exclusive to these conditions, the distinctive manifestations of these disorders likely result from different molecular mechanisms. For instance, as commented in a recent report, the cardiac phenotypes in patients with Noonan syndrome and those with multiple lentigines LEOPARD syndrome with PTPN11 mutations are rather dissimilar, with pulmonary valve stenosis prevailing in the former and hypertrophic cardiomyopathy in the latter.18 We examined the PTPN11 gene in a consecutive series …

MULTIPLE lentigenes have been reported in association with a variety of abnormalities and a familial occurrence. It is likely, on the basis of the following literature review and additional case material, that multiple lentigenes commonly represent one facet of a more generalized hereditary syndrome. Zeisler and Becker 1 described a 24-year-old woman who experienced a marked increase in number of lentigenes from birth to puberty. There were none on the face, but otherwise they were generally distributed. The patient also had pectus carinatum, ocular hypertelorism, and mandibular prognathism. Rosen 2 reported three siblings (two male and one female) with large numbers of lentigenes, but no mention was made of other disorders. A large pedigree in which eight individuals in three generations had lentigenes was reported by Pipkin and Pipkin. 3 Seven affected members had nystagmus, and photographs of some members gave evidence of mandibular prognathism. The pedigrees suggested an autosomal

AT THE meeting of the Mid-Western Society for Pediatric Research in 1962, I reported on nine patients with remarkably similar facies with a previously unrecognized syndrome of valvular pulmonary stenosis and multiple extra cardiac anomalies.1Review of the literature at that time showed that several males resembling these patients had been reported under several different headings, most commonly under the designation of, "the male Turner syndrome."2-5There were no definite reports of similarly affected female patients. In that report I spoke in terms of a "new syndrome" in order to stress that this condition could affect not only males but also females, and that it was also clinically and etiologically different from the true Turner6syndrome. Since that time, a further eight patients, five males and three females, with valvular pulmonary stenosis and similar associated lesions have been studied. An additional two patients, one of each sex