DiagnosisClinical DiagnosisThe diagnosis of LEOPARD syndrome (LS) is made on clinical grounds, by observation of key features.Gorlin et al [1969] named the disorder as an acronym alluding to the cardinal features lentigines, ECG conduction abnormalities, ocular hypertelorism, pulmonic stenosis, abnormal genitalia, retardation of growth, and sensorineural deafness.Additional features occurring frequently in LS:Variable degree of cognitive deficits Skeletal anomalies Hypertrophic cardiomyopathy Voron et al [1976] proposed diagnostic criteria for LS: Multiple lentigines plus two of the other cardinal features
ORIn the absence of lentigines, three of the other cardinal features plus a first-degree relative with LS TestingChromosome analysis. Affected individuals have normal chromosome studies. Molecular Genetic TestingGenes. PTPN11, RAF1, and BRAF are the genes known to be associated with LS. Other loci. It is likely that one or more additional, as-yet undefined genes, possibly related to RAS signal transduction, are associated with the 5% of LS cases without PTPN11, RAF1, or BRAF mutations. Clinical testing PTPN11 Sequence analysis of coding exons 7, 12, and 13 detects missense mutations in about 90% of individuals tested [Digilio et al 2002, Legius et al 2002, Sarkozy et al 2009].Deletion/duplication analysis. No exonic or whole-gene deletions or duplications involving PTPN11 as causative of LS have been reported. Based on the pathogenetic mechanism, intragenic or whole-gene deletions or duplications are not expected to occur in LS.RAF1 Sequence analysis of coding exons 6, 13, and 16 detects all reported missense mutations [Pandit et al 2007]. Deletion/duplication analysis. No exonic or whole-gene deletions or duplications involving RAF1 as causative of LS have been reported. Based on the pathogenetic mechanism, intragenic or whole-gene deletions or duplications are not expected to occur in LS.BRAF Sequence analysis of all coding exons detected missense mutations in two individuals with clinical features fitting LS [Sarkozy et al 2009, Koudova et al 2009]. Table 1. Summary of Molecular Genetic Testing Used in LEOPARD SyndromeView in own windowGene SymbolProportion of LEOPARD Syndrome Attributed to Mutations in This GeneTest MethodMutations DetectedMutation Detection Frequency by Test Method ^{1Test AvailabilityPTPN1190%Sequence analysis of select exons (i.e., coding exons 7, 12, and 13) 2Sequence variants 3 >90%ClinicalSequence analysisSequence variants 3>90%Deletion/duplication analysis 4Exonic or whole-gene deletions 5Unknown 5RAF1Sequence analysis of select exons (i.e., coding exons 6, 13 and 16) 2Sequence variants 3 in selected coding exons >90%ClinicalSequence analysisSequence variants 3>90%Deletion/duplication analysis 4Exonic or whole-gene deletions 5Unknown 5BRAFSequence analysis of select exons (i.e., coding exons 6, and 11 to 17) 2Sequence variants 3 in selected coding exons>90%ClinicalSequence analysisSequence variants 3>90%1. The ability of the test method used to detect a mutation that is present in the indicated gene2. Exons selected for testing may vary among laboratories.3. Examples of mutations detected by sequence analysis may include small intragenic deletions/insertions and missense, nonsense, and splice site mutations.4. Testing that identifies deletions/duplications not readily detectable by sequence analysis of genomic DNA; a variety of methods including quantitative PCR, long-range PCR, multiplex ligation-dependent probe amplification (MLPA), or targeted array GH (gene/segment-specific) may be used. A full array GH analysis that detects deletions/duplications across the genome may also include this gene/segment. 5. No exonic or whole-gene deletions or duplications involving PTPN11or RAF1 as causative of LEOPARD syndrome have been reported. Based on the molecular mechanisms implicated in disease pathogenesis, exonic or whole-gene deletions or duplications are not expected to cause LS.Interpretation of test results. For issues to consider in interpretation of sequence analysis results, click here.Testing StrategyTo confirm/establish the diagnosis in a proband. The diagnosis of LS is made on clinical grounds by observation of key features. Molecular genetic testing can be used to confirm the diagnosis. The following order of testing is recommended:1.PTPN11 sequence analysis of coding exons 7, 12, and 13. These exons encompass all the codons of the PTPN11 gene identified to be mutated in LS thus far. 2.If no mutation is identified, sequence analysis of coding exons 6, 13, and 16 of RAF1 and coding exons 6 and exons 11 to 17 of BRAF. 3.If no mutation is identified, sequence analysis of the remaining coding exons of PTPN11, RAF1, and BRAF. Deletion/duplication analysis is not recommended because the mutation detection frequency is unknown.Prenatal diagnosis and preimplantation genetic diagnosis (PGD) for at-risk pregnancies require prior identification of the disease-causing mutation in the family.Genetically Related (Allelic) DisordersThe phenotypic overlap that occurs in mutations in genes causing LEOPARD syndrome, Noonan syndrome, and cardiofaciocutaneous syndrome emphasizes that these disorders, previously defined as distinct clinical entities, constitute a phenotypic continuum and yet highlights the usefulness of phenotype-based management: PTPN11 Noonan syndrome (NS) (short stature, congenital heart defect, broad or webbed neck, pectus deformities, developmental delay of variable degree, cryptorchidism, and characteristic facies) is an autosomal dominant condition with variable expression. It shows significant overlap with LS, but affected individuals are unlikely to have the profusion of pigmented lesions, lentigines, and café au lait patches or to be deaf. Mutations in exons 2-14 of PTPN11 have been reported in approximately 50% of individuals with NS. These reports confirm that LS and NS are allelic conditions but that particular genotype-phenotype correlations exist with certain mutations in PTPN11 leading to the pigmentary changes and higher prevalence of HCM observed in LS. NS is genetically heterogeneous, with mutations also identified in KRAS, NRAS, SOS1, RAF1, and BRAF (<20% of cases). Leukemia and solid tumors. Juvenile myelomonocytic leukemia (JMML) accounts for one third of childhood cases of myelodysplastic syndrome (MDS) and about 2% of leukemia. Mutations in NRAS, KRAS, and NF1 have been shown to deregulate the RAS/MAPK pathway leading to JMML in about 40% of cases. Somatic mutations in exons 3 and 13 of PTPN11 have been demonstrated in 34% of a cohort of individuals with JMML [Tartaglia et al 2003b]. Mutations in exon 3 were also found in 19% of children with MDS with an excess of blast cells, which often evolves into acute myeloid leukemia (AML) and is associated with poor prognosis. Nonsyndromic AML, especially the monocyte subtype FAB-M5, has been shown to be caused by PTPN11 mutations. All of these mutations cause gain of function in protein tyrosine phosphatase non-receptor type 11 (SHP-2), likely leading to an early initiating lesion in JMML oncogenesis with increased cell proliferation attributable, in part, to prolonged activation of the RAS/MAPK pathway.
The spectrum of leukemogenesis associated with PTPN11 mutations has been extended to include childhood acute lymphoblastic leukemia (ALL). Mutations were observed in 8% of B-cell precursor ALL cases, but not among children with T-lineage ALL [Tartaglia et al 2004b]. Additionally, SHP-2-activating PTPN11 mutations have been found rarely in solid tumors including breast, lung, and gastric neoplasms and neuroblastoma [Bentires-Alj et al 2004].Noonan-like/multiple giant-cell lesion syndrome (NL/MGCLS) is characterized by some cardinal features of NS in association with giant cell lesions of bone and soft tissues (cherubism). PTPN11 mutations have been described in both familial and simplex (i.e., a single occurrence in a family) cases.
Sarkozy et al [2004] reported a girl whose early phenotype was typical of NS but who over time developed the hearing loss and lentigines characteristic of LS. Thus, NL/MGCLS may be too limited and inaccurate a term; a variety of PTPN11 mutations, some of them programming the phenotype of NS and others the phenotype of LS, may also program the development of giant cell lesions.
Overall, NL/MGCLS-associated PTPN11 mutations have been observed in individuals with NS, LS, or cardiofaciocutaneous syndrome (CFCS), including families segregating the trait without any bony involvement. Thus, additional genetic factors may be necessary for the giant cell proliferation to occur. Consistent with this view, this trait is genetically heterogeneous with documented germline mutations affecting other NS/CFCS disease genes coding for transducers participating in the RAS-MAPK signalling pathway [Beneteau et al 2009, Hanna et al 2009, Neumann et al 2009].RAF1 Noonan syndrome (NS) is also associated with RAF1 germline mutations, with a prevalence ranging between 5% and 15% [Pandit et al 2007, Razzaque et al 2007]. RAF1 mutations underlying NS or LS affect residues clustering in three regions of the protein: The N-terminal consensus 14-3-3 recognition sequence (residues 256 to 261) or adjacent residues. Amino acid substitutions within this region account for approximately 70% of all RAF1 mutations. Asp486 and Thr491 are residues within the activation segment region of the kinase domain; alterations in these amino acids constitute approximately 15% of RAF1 mutations. Of note, these same amino acids are mutated in the BRAF gene in solid tumors, thereby altering the functional activation segment; in BRAF the mutations are p.Asp594Gly and p.Thr599Ile [Pandit et al 2007].Mutation of two adjacent residues (Ser612 and Leu613) account for 15% of RAF1 mutations. These two residues are located at the C-terminus in proximity of Ser621, a residue that undergoes phosphorylation and is important for the regulation of the catalytic activation of RAF1. Almost none of the RAF1 residues mutated in NS (and LS) are altered in cancer. A large percentage (70%-90%) of persons with NS and a RAF1 mutation have hypertrophic cardiomyopathy (HCM), which is significantly lower than the 20% with HCM observed in the general NS population. Moreover, this genotype-phenotype correlation seems to be domain-specific, as HCM appears to be associated with mutations affecting the N-terminal 14-3-3 consensus site or the C-terminus.BRAF Cardiofaciocutaneous syndrome (CFCS). Mutations in four genes in the MAPK pathway (BRAF, KRAS, MEK1, and MEK2) have been demonstrated in individuals with CFCS [Niihori et al 2006, Rodriguez-Viciana et al 2006]. BRAF is mutated in 50%-75% of persons with CFCS [Niihori et al 2006, Rodriguez-Viciana et al 2006, Sarkozy et al 2009]. CFCS and LS have similar cardiac findings; however, in CFCS, intellectual disability is usually more severe, with a higher likelihood of structural central nervous system anomalies; more florid skin pathology; and more severe and long-lasting gastrointestinal problems. In CFCS facial appearance tends to be coarser; dolichocephaly and absent eyebrows are more common; and blue eyes are less common. Analysis of the clinical features of persons with CFCS who are BRAF mutation positive indicated a wide phenotypic variability, although all displayed typical dysmorphic facies, cardiac defects, and skin and skeletal anomalies. Moderate-to-severe intellectual disability, observed in most, is commonly associated with seizures or hypotonia. Pigmentary changes including café-au-lait spots, nevi, and lentigines are common [Niihori et al 2006, Rodriguez-Viciana et al 2006, Sarkozy et al 2009].Noonan syndrome (NS). BRAF is rarely mutated in NS (~2% of affected individuals) [Sarkozy et al 2009]. The BRAF mutations observed in NS largely do not overlap with those occurring in CFCS, suggesting a genotype-phenotype correlation. Note: No occurrence of the common BRAF oncogenic somatic p.Val600Glu amino acid substitution has been documented to occur as a germline event associated with CFCS, NS, or LS.}

Natural HistoryMales are more likely than females to be affected with LEOPARD syndrome (LS) [Voron et al 1976], either as a result of bias of ascertainment or preferential survival of affected male fetuses, as proposed for Noonan syndrome (NS) [Tartaglia et al 2004a].Dermatologic. Multiple lentigines present as dispersed flat, black-brown macules, mostly on the face, neck and upper part of the trunk with sparing of the mucosa. In general, lentigines do not appear until age four to five years but then increase into the thousands by puberty [Coppin & Temple 1997]. Some individuals with LS do not exhibit lentigines. Café au lait spots are also observed in up to 70%-80% of affected individuals [Digilio et al 2006], usually preceding the appearance of lentigines.Skin hyperelasticity has also been described.Cardiovascular. Approximately 85% of affected individuals have heart defects, which are similar to those observed in NS but with different frequencies [Limongelli et al 2007]. Hypertrophic cardiomyopathy is detected in up to 70% of individuals with heart defects (compared to 25% in NS). It most commonly appears during infancy and can be progressive.Pulmonary valve stenosis is noted in approximately 25% of affected individuals. Abnormalities of the aortic and mitral valves are also observed in a minority of persons with LS.ECG abnormalities, aside from those typically associated with hypertrophic cardiomyopathy, include conduction defects (23%).Facial features. The facial dysmorphism is similar to that of Noonan syndrome although usually milder [Digilio et al 2006]. Features include inverted triangular-shaped face, downslanting palpebral fissures, low-set posteriorly rotated ears with thickened helices, and hypertelorism. The neck can be short with excess nuchal skin and a low posterior hairline. Hearing. Sensorineural hearing deficits are present in approximately 20% of persons with LS. Minimal information is available about the progression of deafness in those with milder degrees of hearing impairment. Growth. Birth weight is usually normal but may be above the 97th percentile. Postnatal growth retardation resulting in short stature is noted in fewer than 50% of affected individuals. Issues such as adult height and response to growth hormone therapy have not been studied in this disorder. Psychomotor development. Intellectual disability, typically mild, is observed in approximately 30% of persons with LS. Specific information concerning the deficits typically found in these children is not available. Genitourinary. Cryptorchidism, unilateral or bilateral, is present in approximately one third of affected males. Other abnormalities including hypospadias, urinary tract defects, and ovarian abnormalities are observed infrequently.

Genotype-Phenotype CorrelationsNo clear-cut genotype-phenotype correlations have been observed among the PTPN11 mutations causing LS.The two RAF1 mutations observed in LS reside in mutational hot spots strongly associated with hypertrophic cardiomyopathy [Pandit et al 2007]. Of note, p.Ser257Leu mutation was associated with both NS and LS [Pandit et al 2007].In addition to LS in two persons, one third of persons with NS and a RAF1 mutation had other findings including multiple nevi, lentigines and/or café-au-lait spots, suggesting a predisposition to hyperpigmented cutaneous lesions associated with these mutations. Koudova et al [2009] reported a person with LS and normal intelligence who had a novel sequence change in BRAF, further illustrating that the phenotypic spectrum caused by BRAF mutations is broader than previously assumed and does not always include intellectual disability.

Differential DiagnosisTurner syndrome, found only in females, is distinguished from LEOPARD syndrome (LS) by demonstration of an X-chromosome abnormality on cytogenetic studies. The characteristic facial features are also distinct, and in Turner syndrome renal anomalies are more common, developmental delay is much less frequently found, and left-sided heart defects are the rule. The Watson syndrome phenotype also overlaps with that of neurofibromatosis type 1 and the two are now known to be allelic. Variably present in both Watson syndrome and LS are short stature, pulmonary valve stenosis, variable intellectual development, and skin pigment changes including café au lait patches. Lentigines are not described in Watson syndrome.Costello syndrome (CS) shares features with LS, NS, and CFCS. Two series of individuals with CS have been studied molecularly and no PTPN11 mutation has been identified [Tartaglia et al 2003a, Tröger et al 2003]. Germline mutations occurring in the first and third coding exons of the HRAS proto-oncogene have been shown to cause CS [Aoki et al 2005]. Other. LS should be distinguished from other syndromes with developmental delay, short stature, congenital heart defects, and distinctive facies, especially Williams syndrome. Note to clinicians: For a patient-specific ‘simultaneous consult’ related to this disorder, go to , an interactive diagnostic decision support software tool that provides differential diagnoses based on patient findings (registration or institutional access required).

ManagementEvaluations Following Initial DiagnosisTo establish the extent of disease in an individual diagnosed with LEOPARD syndrome (LS), the following evaluations are recommended:Complete physical and neurologic examination Plotting of growth parameters on Noonan syndrome growth charts by Witt et al [1986] (Specific growth charts for LS are not available.) Cardiac evaluation with echocardiography and electrocardiography Ophthalmologic evaluation Hearing evaluation including complete assessment of auditory acuity using age-appropriate tests (e.g., ABR testing, auditory steady-state response (ASSR) testing, pure tone audiometry) Renal ultrasound examination; urinalysis if urinary tract abnormalities are identified Clinical and radiographic assessment of spine and rib cage Brain and cervical spine MRI if neurologic symptoms are present Multidisciplinary developmental evaluation Genetics consultation Treatment of ManifestationsTreatment of cardiovascular anomalies and cryptorchidism is usually the same as in the general population.Treatment of hearing loss may include the following:Fitting with appropriate hearing aids Enrollment in an appropriate educational program for the hearing impaired Consideration for cochlear implantation, a promising habilitation option for persons with profound deafness Recognition that, as distinct from many clinical conditions, the management and treatment of severe-to-profound congenital deafness involves primarily the social welfare and educational systems rather than the medical care system [Smith et al 2005] Any developmental disability should be addressed by early intervention programs and individualized education strategies.Treatment of cryptorchidism in males is usually the same as in the general population.SurveillanceIf anomalies are found in any system, periodic follow-up should be planned and lifelong monitoring may be necessary, especially of cardiovascular abnormalities.For hearing loss, twice-yearly examination by a physician familiar with hereditary hearing impairment and repeat audiometry to confirm the stability of the hearing loss are recommended.Evaluation of Relatives at RiskSee Genetic Counseling for issues related to testing of at-risk relatives for genetic counseling purposes.Therapies Under InvestigationSearch ClinicalTrials.gov for access to information on clinical studies for a wide range of diseases and conditions. Note: There may not be clinical trials for this disorder.

Molecular GeneticsInformation in the Molecular Genetics and OMIM tables may differ from that elsewhere in the GeneReview: tables may contain more recent information. —ED.Table A. LEOPARD Syndrome: Genes and DatabasesView in own windowGene SymbolChromosomal LocusProtein NameLocus SpecificHGMDPTPN1112q24​.13Tyrosine-protein phosphatase non-receptor type 11Catalogue of Somatic Mutations in Cancer (COSMIC)
PTPN11base: Database for pathogenic mutations in the SHP-2 SH2 domain
PTPN11 homepage - Mendelian genesPTPN11BRAF7q34B-Raf proto-oncogene serine/threonine-protein kinaseCatalogue of Somatic Mutations in Cancer (COSMIC)
BRAF homepage - Mendelian genesBRAFRAF13p25​.2RAF proto-oncogene serine/threonine-protein kinaseCatalogue of Somatic Mutations in Cancer (COSMIC)RAF1Data are compiled from the following standard references: gene symbol from HGNC; chromosomal locus, locus name, critical region, complementation group from OMIM; protein name from UniProt. For a description of databases (Locus Specific, HGMD) to which links are provided, click here.Table B. OMIM Entries for LEOPARD Syndrome (View All in OMIM) View in own window 151100LEOPARD SYNDROME 1 164757V-RAF MURINE SARCOMA VIRAL ONCOGENE HOMOLOG B1; BRAF 164760V-RAF-1 MURINE LEUKEMIA VIRAL ONCOGENE HOMOLOG 1; RAF1 176876PROTEIN-TYROSINE PHOSPHATASE, NONRECEPTOR-TYPE, 11; PTPN11 611554LEOPARD SYNDROME 2PTPN11Normal allelic variants. The gene has 15 exons. Pathologic allelic variants. See Table 2. Missense mutations in PTPN11 were identified in 90% of individuals with LEOPARD syndrome (LS) examined. Mutations alter residues at or close to the N-SH2/PTP interacting surfaces, which are involved in switching between active and inactive conformations of the protein, and participating in catalysis. Biochemical characterization of a panel of mutants documented that LS-associated mutations impair catalytic activity [Hanna et al 2006, Kontaridis et al 2006, Tartaglia et al 2006]. Table 2. Selected PTPN11 Pathologic Allelic Variants Causing LEOPARD SyndromeView in own windowDNA Nucleotide ChangeProtein Amino Acid ChangeReference Sequencesc.836A>Gp.Tyr279CysNM_002834​.3
NP_002825​.3c.836A>Cp.Tyr279Serc.1381G>Ap.Ala461Thrc.1391G>Cp.Gly464Alac.1403C>Tp.Thr468Met c.1492C>Tp.Arg498Leuc.1493G>Tp.Arg498Trpc.1517A>Cp.Gln506Proc.1528C>Gp.Gln510GluSee Quick Reference for an explanation of nomenclature. GeneReviews follows the standard naming conventions of the Human Genome Variation Society (www​.hgvs.org).Normal gene product. PTPN11 encodes tyrosine-protein phosphatase non-receptor type 11 (also known as protein tyrosine phosphatase non-receptor type 11, or SHP-2), a widely expressed intracellular protein. The protein is a key molecule in the cellular response to growth factors, hormones, cytokines, and cell adhesion molecules [Neel et al 2003]. It is required in several intracellular signal transduction pathways that control diverse developmental processes (including cardiac semilunar valvulogenesis and blood cell progenitor commitment and differentiation) and has a role in modulating cellular proliferation, differentiation, migration, and apoptosis. The protein has two tandemly arranged SRC-homology 2 (SH2) domains at the N-terminus (N-SH2 and C-SH2), a single catalytic protein tyrosine phosphatase (PTP) domain, and a C-terminal tail with two tyrosyl phosphorylation sites and a proline-rich stretch. The N-SH2-PTP interaction maintains the protein in an inactive state. Abnormal gene product. Aberrant function of SHP-2 causes dysregulation of growth factor and cytokine-mediated RAS/ERK/MAPK and PI3K/AKT signal flow, perturbing cell proliferation [Fragale et al 2004, Chan et al 2005, Keilhack et al 2005, Hanna et al 2006, Kontaridis et al 2006]. RAF1 Normal allelic variants. Human RAF1 comprises 17 exons. It has three conserved regions (CR). CR1, exons 2-5, contains a RAS-binding domain (RBD) and a cysteine-rich domain (CRD). CR2 lies in exon 7, while CR3, which spans exons 10-17, contains the kinase domain and its regulatory element, the activation segment. The gene is highly regulated with numerous serine and threonine residues that can be phosphorylated, resulting in activation or inactivation. The serine at residue 259, which is in CR2, is particularly important. In the inactive state, the N-terminus of RAF1 interacts with and inactivates the kinase domain at the C-terminus. This conformation is stabilized by 14-3-3 protein dimers that bind to phosphorylated Ser259 and Ser261. Dephosphorylation of Ser259 facilitates binding of RAF1 to RAS-GTP and propagation of the signal through the RAS-MAPK cascade via RAF1 MEK kinase activity. Pathologic allelic variants. See Table 3. The consensus 14-3-3 recognition site includes residues Arg256, Ser257, Ser259, and Pro261, and is encoded by exon 7 (coding exon 6). One mutation identified in LS (p.Ser257Leu) altered this CR2 domain, interfered with 14-3-3 binding, and caused greater kinase activity than wild-type protein, both basally and after stimulation [Pandit et al 2007]. The other LS-associated mutation, p.Leu613Val, altered the C-terminal portion of RAF1 (coding exon 16). This mutation also caused greater kinase activity than wild-type protein, both basally and after EGF stimulation.Table 3. RAF1 Pathologic Allelic Variants Causing LEOPARD SyndromeView in own windowDNA Nucleotide ChangeProtein Amino Acid ChangeReference Sequencec.770C>Tp.Ser257LeuNM_002880​.2
NP_002871​.1 c.1837C>Gp.Leu613ValSee Quick Reference for an explanation of nomenclature. GeneReviews follows the standard naming conventions of the Human Genome Variation Society (www​.hgvs.org). Normal gene product. RAF1 is ubiquitously expressed and encodes a protein of 648 amino acids with three domains. CR1 contains a Ras-binding domain; CR2 is a site of regulatory phosphorylation and association with the 14-3-3 protein. CR1 and CR2 both have negative regulatory function, removal of which results in oncogenic activity. The kinase domain, CR3, also associates with 14-3-3. Abnormal gene product. LS-associated RAF1 mutations increase and prolong RAS downstream signaling through enhanced kinase activity, leading to increased activation of MAP kinase kinases (MEK1 and 2). BRAF Pathologic allelic variants. Two germline missense changes affecting exon 6 have been reported in two persons with a diagnosis of LS (see Table 4) [Koudova et al 2009, Sarkozy et al 2009]. Table 4. BRAF Pathologic Allelic Variants Causing LEOPARD SyndromeView in own windowDNA Nucleotide ChangeProtein Amino Acid ChangeReference Sequencec.721A>Cp.Thr241ProNM_004333​.4
NP_004324​.2 c.735A>Tp.Leu245PheSee Quick Reference for an explanation of nomenclature. GeneReviews follows the standard naming conventions of the Human Genome Variation Society (www​.hgvs.org). Normal gene product. Human BRAF comprises 18 coding exons. Exons 3-6, encode a RAS-binding domain (RBD) and a cysteine-rich domain (CRD), while the kinase domain is encoded by exons 11-17. BRAF is ubiquitously expressed and encodes a protein of 766 amino acids. It is activated following GTP-bound RAS binding, and phosphorylates and activates the dual specificity mitogen-activated protein kinase kinases (MEK1 and MEK2).Abnormal gene product. The LS-associated p.Thr241Pro BRAF mutation enhances RAS signaling through increased activation of MEK and ERK kinases [Sarkozy et al 2009]. NIH-3T3 cell colony focus formation assay data indicate that associated (p.Thr241Pro) BRAF mutants do not confer enhanced transformation to cells [Sarkozy et al 2009].