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Investigation of gene dosage imbalances in patients with Noonan syndrome using multiplex ligation-dependent probe amplification analysis
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Genetics and Pathology. (Bondeson/Annerén)
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology, Medical Genetics. (Bondeson/Annerén)
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology, Medical Genetics.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology, Molecular tools.
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2010 (English)In: European Journal of Medical Genetics, ISSN 1769-7212, E-ISSN 1878-0849, Vol. 53, no 3, 117-121 p.Article in journal (Refereed) Published
Abstract [en]

The RAS-MAPK syndromes are a group of clinically and genetically related disorders caused by dysregulation of the RAS-MAPK pathway. A member of this group of disorders, Noonan syndrome (NS), is associated with several different genes within the RAS-MAPK pathway. To date, mutations in PTPN11, SOS1, KRAS, RAF1 and SHOC2 are known to cause NS and a small group of patients harbour mutations in BRAF, MEK1 or NRAS. The majority of the mutations are predicted to cause an up-regulation of the pathway; hence they are gain-of-function mutations. Despite recent advances in gene identification in NS, the genetic aetiology is still unknown in about of patients.To investigate the contribution of gene dosage imbalances of RAS-MAPK-related genes to the pathogenesis of NS, a multiplex ligation-dependent probe amplification (MLPA) assaywas developed. Two probe sets were designed for seven RAS-MAPK-syndrome-related candidate genes: PTPN11, SOS1, RAF1, KRAS, BRAF, MEK1 and MEK2. The probe sets were validated in 15 healthy control individuals and in glioma tumour cell lines. Subsequently, 44 NS patients negative for mutations in known NS-associated genes were screened using the two probe sets. The MLPA results for the patients revealed no gene dosage imbalances. In conclusion, the present results exclude copy number variation of PTPN11, SOS1, RAF1, KRAS, BRAF, MEK1 and MEK2 as a common pathogenic mechanism of NS. The validated and optimised RAS-MAPK probe sets presented here enable rapid high throughput screening of further patients with RAS-MAPK syndromes.

Place, publisher, year, edition, pages
2010. Vol. 53, no 3, 117-121 p.
Keyword [en]
multiplex ligation- dependent probe amplification, MLPA, NS, CFC, RAS-MAPK, Noonan syndrome
National Category
Medical Genetics
Research subject
Clinical Genetics
Identifiers
URN: urn:nbn:se:uu:diva-100760DOI: 10.1016/j.ejmg.2010.03.001ISI: 000281579400001PubMedID: 20302979OAI: oai:DiVA.org:uu-100760DiVA: diva2:210979
Available from: 2009-04-07 Created: 2009-04-07 Last updated: 2017-12-13Bibliographically approved
In thesis
1. RAS-MAPK syndromes - a Clinical and Molecular Investigation
Open this publication in new window or tab >>RAS-MAPK syndromes - a Clinical and Molecular Investigation
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The RAS-MAPK syndromes are a group of clinically and genetically related disorders, characterized by cardiac defects, facial dysmorphism, cutaneous abnormalities and neurocognitive impairment. The pathogenesis is dysregulation of the RAS-MAPK pathway, and several genes within the pathway are involved.

The present thesis aimed at identifying genetic causes in three of the RAS-MAPK syndromes - Noonan syndrome (NS), cardio-facio-cutaneous syndrome (CFC) and Neurofibromatosis-Noonan syndrome (NFNS) - and at correlating genotype with phenotype.

A mutation analysis of six genes associated with the RAS-MAPK syndromes in NS and CFC patients revealed mutations in 10/31 patients. The results suggested more complex genetic overlap and genetic heterogeneity among these syndromes than previously believed. Subsequently, gene dosage imbalances of seven RAS-MAPK-syndrome-related genes were investigated in mutation-negative patients. A multiplex ligation-dependent probe amplification strategy was developed that excluded copy number changes of these genes as a common mechanism in NS.

Genetic causes of clinical variability in NS were investigated where an atypical and severe NS patient was described. In addition, multiple café-au-lait (CAL) spots affected the patient and four otherwise healthy family members. Molecular analysis of four candidate genes revealed a previously described de novo PTPN11 mutation and an inherited NF1 variant in the patient. Neither of them explained the CAL spots trait, which consequently represented a distinct entity. The results suggested that the atypical and severe phenotype in the patient could be a consequence of an additive effect.

Finally, a family displaying NFNS was investigated clinically and molecularly revealing a novel mutation in the GAP-domain of NF1. Furthermore, the results suggested that other RAS-MAPK-syndrome-related genes are not involved in NFNS. A proposal of prioritizing the GAP-domain of NF1 in NFNS was presented.

Conclusively, these studies contribute to further understanding of the RAS-MAPK syndromes and facilitate the diagnostic process and future prognosis prediction.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 92 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 452
Keyword
RAS-MAPK syndromes, Noonan syndrome, Neurofibromatosis type I, cardio-facio-cutaneous syndrome, mutation, multiplex ligation-dependent probe amplification, gene
National Category
Medical Genetics
Research subject
Clinical Genetics
Identifiers
urn:nbn:se:uu:diva-100804 (URN)978-91-554-7508-6 (ISBN)
Public defence
2009-05-20, Rudbecksalen, Rudbecklaboratoriet, Dag Hammarskjölds väg 20, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2009-04-29 Created: 2009-04-07 Last updated: 2011-02-24Bibliographically approved

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Ekvall, SaraThuresson, Ann-CharlotteKamali-Moghaddam, MasoodWestermark, BengtAnnerén, GöranBondeson, Marie-Louise

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