Dataset Information

1p13.2 deletion displays clinical features overlapping Noonan syndrome, likely related to NRAS gene haploinsufficiency.

ABSTRACT: Deletion-induced hemizygosity may unmask deleterious autosomal recessive variants and be a cause of the phenotypic variability observed in microdeletion syndromes. We performed complete exome sequencing (WES) analysis to examine this possibility in a patient with 1p13.2 microdeletion. Since the patient displayed clinical features suggestive of Noonan Syndrome (NS), we also used WES to rule out the presence of pathogenic variants in any of the genes associated with the different types of NS. We concluded that the clinical findings could be attributed solely to the 1p13.2 haploinsufficiency. Retrospective analysis of other nine reported patients with 1p13.2 microdeletions showed that six of them also presented some characteristics of NS. In all these cases, the deleted segment included the NRAS gene. Gain-of-function mutations of NRAS gene are causally related to NS type 6. Thus, it is conceivable that NRAS haploinsufficiency and gain-of-function mutations may have similar clinical consequences. The same phenomenon has been described for two other genes belonging to the Ras/MAPK pathway: MAP2K2 and SHOC2. In conclusion, we here report genotype-phenotype correlations in patients with chromosome 1p13.2 microdeletions and we propose that NRAS may be a critical gene for the NS characteristics in the patients.

SUBMITTER: Linhares ND

PROVIDER: S-EPMC5004838 | biostudies-literature | 2016 Jul-Sep

REPOSITORIES: biostudies-literature

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1p13.2 deletion displays clinical features overlapping Noonan syndrome, likely related to NRAS gene haploinsufficiency.

Linhares Natália Duarte ND Freire Maíra Cristina Menezes MC Cardenas Raony Guimarães Corrêa do Carmo Lisboa RG Pena Heloisa Barbosa HB Lachlan Katherine K Dallapiccola Bruno B Bacino Carlos C Delobel Bruno B James Paul P Thuresson Ann-Charlotte AC Annerén Göran G Pena Sérgio D J SD

Genetics and molecular biology 20160701 3

Deletion-induced hemizygosity may unmask deleterious autosomal recessive variants and be a cause of the phenotypic variability observed in microdeletion syndromes. We performed complete exome sequencing (WES) analysis to examine this possibility in a patient with 1p13.2 microdeletion. Since the patient displayed clinical features suggestive of Noonan Syndrome (NS), we also used WES to rule out the presence of pathogenic variants in any of the genes associated with the different types of NS. We c ...[more]

PMID: 27561113

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Project description:BackgroundNoonan syndrome (NS), a heterogeneous developmental disorder associated with variable clinical expression including short stature, congenital heart defect, unusual pectus deformity and typical facial features, is caused by activating mutations in genes involved in the RAS-MAPK signaling pathway.Case presentationHere, we present a clinical and molecular characterization of a small family with Noonan syndrome. Comprehensive mutation analysis of NF1, PTPN11, SOS1, CBL, BRAF, RAF1, SHOC2, MAP2K2, MAP2K1, SPRED1, NRAS, HRAS and KRAS was performed using targeted next-generation sequencing. The result revealed a recurrent mutation in NRAS, c.179G > A (p.G60E), in the index patient. This mutation was inherited from the index patient's father, who also showed signs of NS.ConclusionsWe describe clinical features in this family and review the literature for genotype-phenotype correlations for NS patients with mutations in NRAS. Neither of affected individuals in this family presented with juvenile myelomonocytic leukemia (JMML), which together with previously published results suggest that the risk for NS individuals with a germline NRAS mutation developing JMML is not different from the proportion seen in other NS cases. Interestingly, 50% of NS individuals with an NRAS mutation (including our family) present with lentigines and/or Café-au-lait spots. This demonstrates a predisposition to hyperpigmented lesions in NRAS-positive NS individuals. In addition, the affected father in our family presented with a hearing deficit since birth, which together with lentigines are two characteristics of NS with multiple lentigines (previously LEOPARD syndrome), supporting the difficulties in diagnosing individuals with RASopathies correctly. The clinical and genetic heterogeneity observed in RASopathies is a challenge for genetic testing. However, next-generation sequencing technology, which allows screening of a large number of genes simultaneously, will facilitate an early and accurate diagnosis of patients with RASopathies.

Dataset Information

1p13.2 deletion displays clinical features overlapping Noonan syndrome, likely related to NRAS gene haploinsufficiency.

Publications

1p13.2 deletion displays clinical features overlapping Noonan syndrome, likely related to NRAS gene haploinsufficiency.

Similar Datasets

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