In mammals both RNase H1 and H2 are required for cell viability and for embryonic development, and mutations in any of the three subunits of RNase H2 have been reported to cause the neuro-inflammatory disease Aicardi-Goutières syndrome (AGS) [19], [20], [21], [22]. Here, RNASEH1 is linked to Aicardi-Goutieres syndrome.