title: Germline missense mutations affecting KRAS Isoform B are associated with a severe Noonan syndrome phenotype.
abstract: Noonan syndrome (NS) is a developmental disorder characterized by short stature, facial dysmorphia, congenital heart disease, and multiple skeletal and hematologic defects. NS is an autosomal dominant trait and is genetically heterogeneous. Gain of function of SHP-2, a protein tyrosine phosphatase that positively modulates RAS signaling, is observed in nearly 50% of affected individuals. Here, we report the identification of heterozygous KRAS gene mutations in two subjects exhibiting a severe NS phenotype with features overlapping those of cardiofaciocutaneous and Costello syndromes. Both mutations were de novo and affected exon 6, which encodes the C-terminal portion of KRAS isoform B but does not contribute to KRAS isoform A. Structural analysis indicated that both substitutions (Val152Gly and Asp153Val) perturb the conformation of the guanine ring-binding pocket of the protein, predicting an increase in the guanine diphosphate/guanine triphosphate (GTP) dissociation rate that would favor GTP binding to the KRASB isoform and bypass the requirement for a guanine nucleotide exchange factor.
authors.affiliation: Dipartimento di Biologia Cellulare e Neuroscienze, Istituto Superiore di Sanita, Rome, Italy.
authors.forename: Claudio
authors.initials: C
authors.lastname: Carta
authors.forename: Francesca
authors.initials: F
authors.lastname: Pantaleoni
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Bocchinfuso
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Stella
authors.forename: Isabella
authors.initials: I
authors.lastname: Vasta
authors.forename: Anna
authors.initials: A
authors.lastname: Sarkozy
authors.forename: Cristina
authors.initials: C
authors.lastname: Digilio
authors.forename: Antonio
authors.initials: A
authors.lastname: Palleschi
authors.forename: Antonio
authors.initials: A
authors.lastname: Pizzuti
authors.forename: Paola
authors.initials: P
authors.lastname: Grammatico
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Zampino
authors.forename: Bruno
authors.initials: B
authors.lastname: Dallapiccola
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Gelb
authors.forename: Marco
authors.initials: M
authors.lastname: Tartaglia
mesh_terms: D001483:Base Sequence; D017931:DNA Primers; D011905:Genes, ras; D018095:Germ-Line Mutation; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D009634:Noonan Syndrome / Q000235:genetics*; D010641:Phenotype
chemical_list: D017931:DNA Primers