Activating mutations in FGFR3 and HRAS reveal a shared genetic origin for congenital disorders and testicular tumors

Abstract

Andrew Wilkie and colleagues report that activating paternal-effect mutations in FGFR3 and HRAS promote clonal expansion in the testis, leading to spermatocytic seminomas. The same mutation in FGFR3 leads to the lethal disorder thanatophoric dysplasia, revealing a shared genetic mechanism for congenital disorders and testicular tumors. Genes mutated in congenital malformation syndromes are frequently implicated in oncogenesis1,2, but the causative germline and somatic mutations occur in separate cells at different times of an organism's life. Here we unify these processes to a single cellular event for mutations arising in male germ cells that show a paternal age effect3. Screening of 30 spermatocytic seminomas4,5 for oncogenic mutations in 17 genes identified 2 mutations in FGFR3 (both 1948A>G, encoding K650E, which causes thanatophoric dysplasia in the germline)6 and 5 mutations in HRAS. Massively parallel sequencing of sperm DNA showed that levels of the FGFR3 mutation increase with paternal age and that the mutation spectrum at the Lys650 codon is similar to that observed in bladder cancer7,8. Most spermatocytic seminomas show increased immunoreactivity for FGFR3 and/or HRAS. We propose that paternal age-effect mutations activate a common 'selfish' pathway supporting proliferation in the testis, leading to diverse phenotypes in the next generation including fetal lethality, congenital syndromes and cancer predisposition.