Differential rates of germline heterozygote and mosaic variants inNF2may show varying propensity for meiotic or mitotic mutation

Abstract

NF2-related schwannomatosis is an autosomal dominant tumour predisposition condition that causes multiple benign tumours of the nervous system, especially schwannomas. This results from germline pathogenic variants in theNF2gene, which are most commonly de novo NF2 nonsense variants. Over half of these de novo variants occur at just six CpG dinucleotides. In this study, we show that the sixNF2CpG nonsense variants make up 54% (136/252) of de novo nonsense variants, despite constituting <10% of nonsense positions in the germline (total=62), and that this pattern is different from theAPCgene, which is also known to have a high rate of mosaicism. In addition, theNF2c.586C>T; p.(Arg196Ter) has a higher de novo heterozygote to mosaicism ratio than the five other CpG variants (73.1% vs 53.7%, p=0.03) and the neighbouring CpG variant (NF2c.592C>T; p.(Arg198Ter) 38.5%, p=0.02). This may be due to differences in rates of mutation at meiosis versus mitosis.