ClinVar Genomic variation as it relates to human health

The Gly12Cys variant in HRAS has been reported in the literature in six individu als with severe neonatal Costello syndrome (Kerr 2006, Lo 2008, Lin 2009, Niihor i 2011, Lorenz 2012). This variant has been reported to have occurred de novo in one proband (Lorenz 2012). Several other DNA variants affecting codon 12 of HRA S are commonly observed in patients with Costello syndrome (Niihori 2011). There fore, this variant is highly likely to be pathogenic.

Variant summary: HRAS c.34G>T (p.Gly12Cys) results in a non-conservative amino acid change located in the Small GTP-binding protein domain (IPR005225) of the encoded protein sequence. Four of five in-silico tools predict a damaging effect of the variant on protein function. The variant was absent in 250294 control chromosomes (gnomAD). c.34G>T has been reported in the literature in multiple individuals affected with Costello Syndrome (e.g. Niihori_2011, McCormick_2013, Choi_2019). These data indicate that the variant is very likely to be associated with disease. In functional studies, Niihori et al (Niihori_2011) report that there was an increase in guanosine triphosphate (GTP)-bound HRAS and activation of RAS signaling pathway (as measured by the activation of ELK1 and c-Jun) in cells transfected with the variant of interest. In addition, HGMD database reports several other missense variants affecting the same codon and nearby codons (e.g. p.G12R, p.G12S, p.G12V, p.G12A, p.G13D, p.G13C) suggesting this area might be a mutational hotspot. Four ClinVar submitters (evaluation after 2014) cite the variant as pathogenic. Based on the evidence outlined above, the variant was classified as pathogenic.

The variant in c.34G>T (p.Gly12Cys) in HRAS gene is reported as pathogenic for Costello syndrome and other HRAS-related diseases in ClinVar (Variation ID: 12613) and in the Global Variome shared LOVD database v.3.0 (genomic variant: #0000345686). There is no information on frequency in gnomAD or 1000 Genomes Project. The variant has been reported in in multiple individuals affected with Costello Syndrome (Choi et al., 2019, PMID: 31394527; McCormick et al., 2013, PMID: 23429430; Niihori et al., 2011, PMID: 21850009).

Published functional studies of the G12C variant have shown that it results in increased active, GTP-bound HRAS (Niihori et al., 2011); In silico analysis supports that this missense variant has a deleterious effect on protein structure/function; Not observed in large population cohorts (gnomAD); The majority of missense variants in this gene are considered pathogenic (HGMD); This variant is associated with the following publications: (PMID: 16443854, 24224811, 23093928, 24803665, 31394527, 22926243, 21850009, 16155195, 18039947, 33258288, 29493581)

The HRAS c.34G>T; p.Gly12Cys variant (rs104894229; ClinVar Variation ID: 12613) is reported in the literature as a recurrent de novo variant in multiple individuals affected with Costello syndrome (Choi 2019, Kerr 2006, Lorenz 2012). This variant is absent from the Genome Aggregation Database, indicating it is not a common polymorphism. The glycine residues at codons 12 and 13 are frequently altered in both Costello syndrome patients (Aoki 2005, Estep 2006, Gripp 2005, Kerr 2006, Niihori 2011). Functional characterization of the p.Gly12Cys protein indicates increased downstream MEK signaling activity (Niihori 2011), consistent with the established disease mechanism of Costello syndrome. Based on available information, this variant is considered to be pathogenic. References: Choi N et al. Phenotypic and Genetic Characteristics of Five Korean Patients with Costello Syndrome. Cytogenet Genome Res. 2019;158(4):184-191. PMID: 31394527. Kerr B et al. Genotype-phenotype correlation in Costello syndrome: HRAS mutation analysis in 43 cases. J Med Genet. 2006 May;43(5):401-5. PMID: 16443854 Lorenz S et al Two cases with severe lethal course of Costello syndrome associated with HRAS p.G12C and p.G12D. Eur J Med Genet. 2012 Nov;55(11):615-9. PMID: 22926243. Niihori T et al. HRAS mutants identified in Costello syndrome patients can induce cellular senescence: possible implications for the pathogenesis of Costello syndrome. J Hum Genet. 2011 Oct;56(10):707-15. PMID: 21850009.

ACMG Criteria:PP3, PP5, PM2_P, PM1, PM5, PS3; Variant was found in heterozygous state

This sequence change replaces glycine, which is neutral and non-polar, with cysteine, which is neutral and slightly polar, at codon 12 of the HRAS protein (p.Gly12Cys). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individuals with Costello syndrome (PMID: 16443854, 18039947, 22926243). ClinVar contains an entry for this variant (Variation ID: 12613). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is expected to disrupt HRAS protein function. Experimental studies have shown that this missense change affects HRAS function (PMID: 21850009). This variant disrupts the p.Gly12 amino acid residue in HRAS. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 16170316, 16372351, 16443854, 16835863, 17601930, 18042262, 21850009, 22420426, 28027064). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. For these reasons, this variant has been classified as Pathogenic.

Variant classified using ACMG guidelines