RESUMO
Signal transduction through the RAF-MEK-ERK pathway, the first described mitogen-associated protein kinase (MAPK) cascade, mediates multiple cellular processes and participates in early and late developmental programs. Aberrant signaling through this cascade contributes to oncogenesis and underlies the RASopathies, a family of cancer-prone disorders. Here, we report that de novo missense variants in MAPK1, encoding the mitogen-activated protein kinase 1 (i.e., extracellular signal-regulated protein kinase 2, ERK2), cause a neurodevelopmental disease within the RASopathy phenotypic spectrum, reminiscent of Noonan syndrome in some subjects. Pathogenic variants promote increased phosphorylation of the kinase, which enhances translocation to the nucleus and boosts MAPK signaling in vitro and in vivo. Two variant classes are identified, one of which directly disrupts binding to MKP3, a dual-specificity protein phosphatase negatively regulating ERK function. Importantly, signal dysregulation driven by pathogenic MAPK1 variants is stimulus reliant and retains dependence on MEK activity. Our data support a model in which the identified pathogenic variants operate with counteracting effects on MAPK1 function by differentially impacting the ability of the kinase to interact with regulators and substrates, which likely explains the minor role of these variants as driver events contributing to oncogenesis. After nearly 20 years from the discovery of the first gene implicated in Noonan syndrome, PTPN11, the last tier of the MAPK cascade joins the group of genes mutated in RASopathies.
Assuntos
Carcinogênese/genética , Proteína Quinase 1 Ativada por Mitógeno/genética , Transtornos do Neurodesenvolvimento/genética , Síndrome de Noonan/genética , Pré-Escolar , Feminino , Humanos , Sistema de Sinalização das MAP Quinases/genética , Masculino , Mutação de Sentido Incorreto/genética , Transtornos do Neurodesenvolvimento/patologia , Síndrome de Noonan/fisiopatologia , Fenótipo , Proteína Tirosina Fosfatase não Receptora Tipo 11/genética , Transdução de Sinais , Sequenciamento do Exoma , Proteínas ras/genéticaRESUMO
Developmental syndromes are characterized by numerous phenotypical signs and malformations. In most of them such as Turner, Noonan, Prader-Willi, Silver-Russel, Williams, Kabuki, Leri-Weill syndrome and skeletal dysplasias, short stature is a common feature. Growth defect is very often related to a defect in cellular growth, but some unknown abnormality in GH action is possible. Recently, the greater availability of recombinant GH has expanded the interest towards GH secretion and therapy also in developmental syndromes. We recognize syndromes associated with GH deficiency (GHD), showing a developmental midline defect such as Pallister-Hall syndrome, septo-optic dysplasia, but many of these conditions do not have a convincing link with GHD. Moreover, some conditions, in particular the well-studied Turner syndrome, that do not have a real GHD, have proven to benefit from GH therapy at supra-physiological doses obtaining a higher final height than the expected one according to the natural history. This has expanded the indications for GH therapy. The aim of our paper is to review the literature on GH secretion, on the effects and costs-benefits of GH therapy in many dysmorphic syndromes, presenting some results of GH secretion and therapy obtained in our experience.