HRAS mutants identified in Costello syndrome patients can induce cellular senescence: possible implications for the pathogenesis of Costello syndrome

Abstract

Costello syndrome (CS) is a congenital disease that is characterized by a distinctive facial appearance, failure to thrive, mental retardation and cardiomyopathy. In 2005, we discovered that heterozygous germline mutations in HRAS caused CS. Several studies have shown that CS-associated HRAS mutations are clustered in codons 12 and 13, and mutations in other codons have also been identified. However, a comprehensive comparison of the substitutions identified in patients with CS has not been conducted. In the current study, we identified four mutations (p.G12S, p.G12A, p.G12C and p.G12D) in 21 patients and analyzed the associated clinical manifestations of CS in these individuals. To examine functional differences among the identified mutations, we characterized a total of nine HRAS mutants, including seven distinct substitutions in codons 12 and 13, p.K117R and p.A146T. The p.A146T mutant demonstrated the weakest Raf-binding activity, and the p.K117R and p.A146T mutants had weaker effects on downstream c-Jun N-terminal kinase signaling than did codon 12 or 13 mutants. We demonstrated that these mutant HRAS proteins induced senescence when overexpressed in human fibroblasts. Oncogene-induced senescence is a cellular reaction that controls cell proliferation in response to oncogenic mutation and it has been considered one of the tumor suppression mechanisms in vivo. Our findings suggest that the HRAS mutations identified in CS are sufficient to cause oncogene-induced senescence and that cellular senescence might therefore contribute to the pathogenesis of CS.

Clinical and molecular characterization of children with Noonan syndrome and other RASopathies in Argentina

“…Patients with CS have a 13 % probability of developing tumors. 15 It is caused by heterozygous mutations in the HRAS protooncogene in more than 80 % of cases. 16 Given the overlapping clinical features of these syndromes and their variable expression, molecular testing is critical to establish an accurate diagnosis.…”

C4ST-1/CHST11-controlled chondroitin sulfation interferes with oncogenic HRAS signaling in Costello syndrome

“…The MAPK pathways are critical downstream mediators of RAS signal transduction, and have been shown to be upregulated in response to oncogenic HRAS mutations in Costello syndrome. 8,18,38,39 Thus, C7669 fibroblasts were treated with inhibitors of the MAP-kinases Erk (PD98059), p38 (SB203580) and SAPK/JNK (SP600125) for 48 h, and subsequently analyzed for C4ST-1 mRNA expression by qRT-PCR (Figure 2n). Blocking all three MAPK cascades was able to significantly elevate the C4ST-1 expression by approximately 2-to 3.5-fold when compared with a DMSO-treated control.…”

“…Recently, cellular senescence was reported in fibroblasts with forced expression of HRAS-activating mutations. 39 Strikingly, we previously demonstrated that mice homozygous for a C4st-1 loss-of-function …”

A computational panel of pathological RAS mutants with implications for personalized medicine and genetic medicine

“…In years since, the situation has become less clear. Consider that some of the germline mutations in the RASopathy Costello syndrome occur at codon 12 [29] which is also the most common codon mutated in RAS mutations found in cancer [30]. Our analysis demonstrates that the quantity of mutant expressed is an important variable for determining signal strength.…”