Clinical and molecular analysis of 26 individuals with Noonan syndrome in a reference institution in Colombia.

Our aim was to characterize the phenotype and genotype of individuals with Noonan syndrome in Colombia. There are published cohorts of Noonan individuals from several countries in Latin America including Brazil, Chile, and Argentina, but none from Colombia. We described 26 individuals with NS from a single large referral center in the South West of Colombia using an established database in the genetics department and hospital records search using ICD-10 codes. All patients included in this study were evaluated by a medical geneticist and have molecular confirmation of NS diagnosis. The median age at referral was 3.5 years (range, 0-39), and at molecular diagnosis was 5 years (range, 0-40). Patients mostly originated from the southwest region of Colombia (19/26, 73%). Pathogenic variants in PTPN11 are the most common cause of NS in Colombian individuals followed by SHOC2 and SOS1 variants. The prevalence of cardiomyopathy was low in this population compared to other populations. Further research is needed with a larger sample size and including different regions of Colombia to correlate our findings. This study provides new information about time to diagnosis of NS in Colombia, genotypes, and provides important information to help develop guidelines for diagnosis and management of this disease in the region.

Clinical and molecular characterization of children with Noonan syndrome and other RASopathies in Argentina. / Caracterización clínica y molecular de niños con síndrome de Noonan y otras RASopatías en Argentina.

INTRODUCTION: RASopathies are a set of syndromes with phenotypic overlapping features caused by gene mutations involved in the RAS/MAPK pathway. They are autosomal dominantly inherited and share common clinical characteristics, including short stature, craniofacial dysmorphisms, congenital heart disease, ectodermal manifestations, and a higher risk for cancer. A molecular diagnosis is a key factor. OBJECTIVE: To identify PTPN11, SOS1, RAF1, BRAF, and HRAS mutations and compare the main clinical characteristics of patients with molecular confirmation. Population and methods. Children with a clinical diagnosis of RASopathy assessed between August 2013 and February 2017. RESULTS: Mutations were identified in 71 % (87/122) of patients. The molecular test confirmed diagnosis in 73 % of patients with Noonan syndrome. The most prevalent mutation was c.922A>G (p.Asn308Asp) in the PTPN11 gene. A previously undescribed variant in RAF1 was detected: c.1467G>>C (p.Leu489Phe). Cardiofaciocutaneous syndrome was confirmed in 67 % of cases with BRAF mutations. Costello syndrome and Noonan syndrome with multiple lentigines were confirmed in all cases. CONCLUSION: The confirmation of clinical diagnosis allowed for a more accurate differential diagnosis. The prevalence of PTPN11 (58 %), SOS1 (10 %), and RAF1 mutations (5 %) in children with Noonan syndrome, of PTPN11 mutations (100 %) in those with Noonan syndrome with multiple lentigines, of BRAF mutations (67 %) in those with cardiofaciocutaneous syndrome, and of HRAS mutations (100 %) in those with Costello syndrome was determined.

Introducción. Las RASopatías son un conjunto de síndromes fenotípicamente superpuestos causados por mutaciones en genes implicados en la vía RAS/MAPK. La herencia es autosómica dominante, presentan características clínicas comunes, como baja talla, dismorfias craneofaciales, cardiopatía congénita, manifestaciones ectodérmicas y mayor riesgo de cáncer. El diagnóstico molecular es clave. Objetivo. Identificar mutaciones en los genes PTPN11, SOS1, RAF1, BRAF y HRAS, y comparar las principales características clínicas en pacientes con confirmación molecular. Población y métodos. Se estudiaron niños con diagnóstico clínico de RASopatía evaluados entre agosto de 2013 y febrero de 2017. Resultados. Se identificaron mutaciones en el 71 % (87/122) de los pacientes. El estudio molecular confirmó el diagnóstico en el 73 % de los pacientes con síndrome de Noonan. La mutación más prevalente fue c.922A>G (p.Asn308Asp) en el gen PTPN11. Se detectó una variante no descrita en RAF1, c.1467G>C (p.Leu489Phe). Se confirmó el síndrome cardiofaciocutáneo en el 67 % de los casos con mutaciones en el gen BRAF. El síndrome de Costello y el síndrome de Noonan con múltiples lentigos se confirmaron en todos los casos. Conclusión. La confirmación del diagnóstico clínico permitió un diagnóstico diferencial más preciso. Se determinó la prevalencia de las mutaciones en PTPN11 (el 58 %), SOS1 (el 10 %) y RAF1 (el 5 %) en niños con síndrome de Noonan, en PTPN11 (el 100 %) en el síndrome de Noonan con múltiples lentigos, en BRAF (el 67 %) en el síndrome cardiofaciocutáneo y en HRAS (el 100 %) en el síndrome de Costello.

Study of Ras/MAPK pathway gene variants in Chilean patients with Cryptorchidism.

Cryptorchidism is one of the most common congenital disorders in boys, and several genetic, hormonal, and environmental factors have been proposed as possible causes for this genitourinary defect. Genetic factors have been intensively searched, but relatively few pathogenic variants have been described. Cryptorchidism is a frequent finding in patients with RASopathies, a group of syndrome caused by mutations in genes of the Ras/MAPK pathway. Our aim was to determine whether patients with isolated cryptorchidism (IC) exhibit Ras/MAPK pathway gene variants associated with RASopathies. Two hundred thirty-nine patients with IC were recruited after orchidopexy. Determination of Ras/MAPK pathway gene variants was performed by high-resolution melting (HRM) analysis followed by sequencing. Restriction or allele-specific amplification assay was applied to (i) variant confirmation; (ii) search in healthy controls; and (iii) segregation analysis. Controls correspond to 100 healthy Chilean adults without a history of cryptorchidism. Molecular analysis showed one synonymous substitution (BRAF_p.Q456Q) in two patients and four missense substitutions (SOS1_ p.R497Q, BRAF_ p.F595L, NRAS_ p.T50I, and MAP2K2_ p.Y134C) in five patients. Our results suggest that some patients with isolated cryptorchidism, but with no evidence of dysmorphic features suggestive of RASopathies, may harbor Ras/MAPK pathway gene alterations.

Co-occurring PTPN11 and SOS1 gene mutations in Noonan syndrome: does this predict a more severe phenotype? / Coocorrência de mutações nos genes PTPN11 e SOS1 na síndrome de Noonan: este achado prediz um fenótipo mais grave?

Noonan syndrome (NS) is an autosomal dominant disorder, with variable phenotypic expression, characterized by short stature, facial dysmorphisms and heart disease. Different genes of the RAS/MAPK signaling pathway are responsible for the syndrome, the most common are: PTPN11, SOS1, RAF1, and KRAS. The objective of this study was to report a patient with Noonan syndrome presenting mutations in two genes of RAS/MAPK pathway in order to establish whether these mutations lead to a more severe expression of the phenotype. We used direct sequencing of the PTPN11, SOS1, RAF1, and KRAS genes. We have identified two described mutations in heterozygosity: p.N308D and p.R552G in the genes PTPN11 and SOS1, respectively. The patient has typical clinical features similar to the ones with NS and mutation in only one gene, even those with the same mutation identified in this patient. A more severe or atypical phenotype was not observed, suggesting that these mutations do not exhibit an additive effect.

A síndrome de Noonan (SN) é uma doença gênica autossômica dominante, com expressão clínica variável, caracterizada por baixa estatura, dismorfismos faciais e cardiopatia. Diferentes genes da via de sinalização RAS/MAPK são responsáveis pela síndrome, sendo as mais frequentes: PTPN11, SOS1, RAF1 e KRAS. O objetivo deste estudo foi relatar um paciente com SN que apresenta mutações em dois genes da via RAS/MAPK a fim de estabelecer se essas mutações levam a uma expressão mais grave do fenótipo. Utilizou-se sequenciamento direto dos genes PTPN11, SOS1, RAF1 e KRAS. Foram identificadas duas mutações em heterozigose previamente descritas: p.N308D e p.R552G nos genes PTPN11 e SOS1, respectivamente. A paciente apresenta quadro clínico típico semelhante ao dos pacientes com SN e mutação em um único gene, mesmo naqueles com a mesma mutação identificada na paciente. Não foi observado um fenótipo mais grave ou atípico na paciente, sugerindo que as mutações não apresentam um efeito aditivo.

Co-occurring PTPN11 and SOS1 gene mutations in Noonan syndrome: does this predict a more severe phenotype?

Noonan syndrome (NS) is an autosomal dominant disorder, with variable phenotypic expression, characterized by short stature, facial dysmorphisms and heart disease. Different genes of the RAS/MAPK signaling pathway are responsible for the syndrome, the most common are: PTPN11, SOS1, RAF1, and KRAS. The objective of this study was to report a patient with Noonan syndrome presenting mutations in two genes of RAS/MAPK pathway in order to establish whether these mutations lead to a more severe expression of the phenotype. We used direct sequencing of the PTPN11, SOS1, RAF1, and KRAS genes. We have identified two described mutations in heterozygosity: p.N308D and p.R552G in the genes PTPN11 and SOS1, respectively. The patient has typical clinical features similar to the ones with NS and mutation in only one gene, even those with the same mutation identified in this patient. A more severe or atypical phenotype was not observed, suggesting that these mutations do not exhibit an additive effect.

A mutation in the SOS1 gene causes hereditary gingival fibromatosis type 1.

Hereditary gingival fibromatosis (HGF) is a rare, autosomal dominant form of gingival overgrowth. Affected individuals have a benign, slowly progressive, nonhemorrhagic, fibrous enlargement of the oral masticatory mucosa. Genetic loci for autosomal dominant forms of HGF have been localized to chromosome 2p21-p22 (HGF1) and chromosome 5q13-q22 (HGF2). To identify the gene responsible for HGF1, we extended genetic linkage studies to refine the chromosome 2p21-p22 candidate interval to approximately 2.3 Mb. Development of an integrated physical and genetic map of the interval identified 16 genes. Sequencing of these genes, in affected and unaffected HGF1 family members, identified a mutation in the Son of sevenless-1 (SOS1) gene in affected individuals. In this report, we describe the genomic structure of the SOS1 gene and present evidence that insertion of a cytosine between nucleotides 126,142 and 126,143 in codon 1083 of the SOS1 gene is responsible for HGF1. This insertion mutation, which segregates in a dominant manner over four generations, introduces a frameshift and creates a premature stop codon, abolishing four functionally important proline-rich SH3 binding domains normally present in the carboxyl-terminal region of the SOS1 protein. The resultant protein chimera contains the wild-type SOS1 protein for the N-terminal amino acids 1-1083 fused to a novel 22-amino acid carboxyl terminus. Similar SOS1 deletion constructs are functional in animal models, and a transgenic mouse construct with a comparable SOS1 chimera produces a phenotype with skin hypertrophy. Clarification of the functional role of this SOS1 mutant has implications for understanding other forms of gingival fibromatosis and corrective gingival-tissue management.