Journal Article

Contributions of intrinsic mutation rate and selfish selection to levels of de novo HRAS mutations in the paternal germline

Meyts, Ewa Rajpert-De, Looijenga, Leendert H. J., Gregory, Lorna, McGowan, Simon J., Iqbal, Zamin, Shorto, Jennifer, McVean, Gilean, Kerr, Bronwyn, Wilkie, Andrew O. M., Pfeifer, Susanne P., Turner, Karen, Buck, David, Giannoulatou, Eleni, Wright, Emma M. M. Burkitt, Itani, Aysha, Goriely, Anne, Taylor, Indira B., Turner, Isaac, Maher, Geoffrey J.

2013

Overview

The RAS proto-oncogene Harvey rat sarcoma viral oncogene homolog (HRAS) encodes a small GTPase that transduces signals from cell surface receptors to intracellular effectors to control cellular behavior. Although somatic HRAS mutations have been described in many cancers, germline mutations cause Costello syndrome (CS), a congenital disorder associated with predisposition to malignancy. Based on the epidemiology of CS and the occurrence of HRAS mutations in spermatocytic seminoma, we proposed that activating HRAS mutations become enriched in sperm through a process akin to tumorigenesis, termed selfish spermatogonial selection. To test this hypothesis, we quantified the levels, in blood and sperm samples, of HRAS mutations at the p.G12 codon and compared the results to changes at the p.A11 codon, at which activating mutations do not occur. The data strongly support the role of selection in determining HRAS mutation levels in sperm, and hence the occurrence of CS, but we also found differences from the mutation pattern in tumorigenesis. First, the relative prevalence of mutations in sperm correlates weakly with their in vitro activating properties and occurrence in cancers. Second, specific tandem base substitutions (predominantly GC>TT/AA) occur in sperm but not in cancers; genomewide analysis showed that this same mutation is also overrepresented in constitutional pathogenic and polymorphic variants, suggesting a heightened vulnerability to these mutations in the germline. We developed a statistical model to show how both intrinsic mutation rate and selfish selection contribute to the mutational burden borne by the paternal germline.

• Publisher: National Academy of Sciences,NATIONAL ACADEMY OF SCIENCES,National Acad Sciences
• Subject: Adult / Aged / Aging - blood / Aging - genetics / Alleles / Biological Sciences / blood / Cancer / carcinogenesis / Carcinogenesis - genetics / Cellular biology / Codon - genetics / Codons / Congenital diseases / Costello Syndrome - genetics / Epidemiology / Genetic mutation / Genomes / Genomics / Germ cells / Germ Cells - chemistry / Germline mutation / guanosinetriphosphatase / Humans / Male / Middle Aged / Models, Statistical / Mutation / Mutation - genetics / Nucleotides / Paternal age / Proto-Oncogene Mas / Proto-Oncogene Proteins p21(ras) - genetics / proto-oncogenes / rats / receptors / Sarcoma / Selection, Genetic - genetics / Signal transduction / Spermatozoa / Statistical models / Stem cells