Analysis of correlated mutations in Ras G-domain

Duplications in the G3 domain or switch II region in HRAS identified in patients with Costello syndrome

Costello syndrome (CS) is an autosomal-dominant disorder characterized by distinctive facial features, hypertrophic cardiomyopathy, skeletal abnormalities, intellectual disability, and predisposition to cancers. Germline variants in HRAS have been identified in patients with CS. Intragenic HRAS duplications have been reported in three patients with a milder phenotype of CS. In this study, we identified two known HRAS variants, p.(Glu63_Asp69dup), p.(Glu62_Arg68dup), and one novel HRAS variant, p.(Ile55_Asp57dup), in patients with CS, including a patient with craniosynostosis. These intragenic duplications are located in the G3 domain and the switch II region. Cells expressing cDNA with these three intragenic duplications showed an increase in ELK-1 transactivation. Injection of wild-type or mutant HRAS mRNAs with intragenic duplications in zebrafish embryos showed significant elongation of the yolk at 11 h postfertilization, which was improved by MEK inhibitor treatment, and a variety of developmental abnormalities at 3 days post fertilization was observed. These results indicate that small in-frame duplications affecting the G3 domain and switch II region of HRAS increase the activation of the ERK pathway, resulting in developmental abnormalities in zebrafish or patients with CS.

LvRas and LvRap are both important for WSSV replication in Litopenaeus vannamei

The white Spot Syndrome Virus (WSSV) is a pathogen that causes huge economic losses in the shrimp-farming industry globally. At the WSSV genome replication stage (12 hpi) in WSSV-infected shrimp hemocytes, activation of the PI3K-Akt-mTOR pathway triggers metabolic changes that resemble the Warburg effect. In shrimp, the upstream regulators of this pathway are still unknown, and in the present study, we isolate, characterize and investigate two candidate factors, i.e. the shrimp Ras GTPase isoforms LvRas and LvRap, both of which are upregulated after WSSV infection. dsRNA silencing experiments show that virus replication is significantly reduced when expression of either of these genes is suppressed. Pretreatment with the Ras inhibitor Salirasib further suggests that LvRas, which is a homolog to a commonly overexpressed human oncoprotein, may be involved in regulating the WSSV-induced Warburg effect. We also show that while both the PI3K-Akt-mTOR and Raf-MEK-ERK pathways are activated by WSSV infection, LvRas appears to be involved only in the regulation of the mTOR pathway.