Differential allelic expression of SOS1 and hyperexpression of the activating SOS1 c.755C variant in a Noonan syndrome family

Silvia Moncini, Maria Teresa Bonati, Ilaria Morella, Luca Ferrari, Riccardo Brambilla, Paola Riva

Research output: Contribution to journalArticle

Abstract

Noonan syndrome (NS) is a genetic condition characterized by congenital heart defects, short stature and characteristic facial features. We here present the case of a girl with moderate learning disabilities, delayed language development, craniofacial features and skin anomalies reminiscent of NS. After a mutation screening of the known NS genes PTPN11, SOS1, RAF1, KRAS, GRB2, BRAF and SHOC2 we found the heterozygous c.755T>C variant in SOS1 causing the p.I252T amino-acid substitution, which was considered possibly pathogenetic by bioinformatic predictions. The same variant was present in the proband's mother, displaying some NS features, and mateRNAl grandfather showing no NS traits, but also by a healthy subject in 1000 genomes project database without phenotype informations. The functional analysis revealed that SOS1 c.755C activated the RAS-ERK intracellular pathway, whereas no effects on RAC-JNK cascade have been detected. After a comparison between the sequence of SOS1 cDNA from peripheral blood and SOS1 genomic DNA, we showed for the first time a differential allelic expression of the SOS1 gene in healthy individuals, thus occurring as a physiologic condition. Interestingly, we found that the mutated allele C was 50% more expressed than the wild-type allele T in all familial carriers. The comparable amount of SOS1 mRNA between mutated individuals and the controls indicates that the variant does not affect SOS1 expression. The present study provides a first evidence of allelic imbalance of SOS1 and pinpoints this condition as a possible mechanism underlying a different penetrance of some SOS1-mutated alleles in unrelated carriers.

Original languageEnglish
Pages (from-to)1531-1537
Number of pages7
JournalEuropean Journal of Human Genetics
Volume23
Issue number11
DOIs
Publication statusPublished - Oct 1 2015

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Noonan Syndrome
Alleles
Mothers
Allelic Imbalance
Language Development
Congenital Heart Defects
Penetrance
MAP Kinase Signaling System
Learning Disorders
Amino Acid Substitution
Computational Biology
Healthy Volunteers
Complementary DNA
Genome
Databases
Phenotype
Gene Expression
Messenger RNA
Skin
Mutation

ASJC Scopus subject areas

  • Genetics(clinical)
  • Genetics

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Differential allelic expression of SOS1 and hyperexpression of the activating SOS1 c.755C variant in a Noonan syndrome family. / Moncini, Silvia; Bonati, Maria Teresa; Morella, Ilaria; Ferrari, Luca; Brambilla, Riccardo; Riva, Paola.

In: European Journal of Human Genetics, Vol. 23, No. 11, 01.10.2015, p. 1531-1537.

Research output: Contribution to journalArticle

Moncini, Silvia ; Bonati, Maria Teresa ; Morella, Ilaria ; Ferrari, Luca ; Brambilla, Riccardo ; Riva, Paola. / Differential allelic expression of SOS1 and hyperexpression of the activating SOS1 c.755C variant in a Noonan syndrome family. In: European Journal of Human Genetics. 2015 ; Vol. 23, No. 11. pp. 1531-1537.
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