SAMHD1 and Aicardi-Goutieres syndrome: Interestingly, recent genome-wide studies have demonstrated that RNA/DNA hybrids are particularly enriched at retrotransposon elements in yeast cells [22], suggesting that expansion of retroelements due to mutations in TREX1, ADAR1 or SAMHD1 may lead to increased RNA/DNA hybrid levels, contributing to autoimmunitity in AGS.