SAMHD1 and Aicardi-Goutieres syndrome: On the other hand, SAMHD1-deficient fibroblasts showed insignificant DRIP-seq read-count enrichment at CD collision sub-regions (adjusted P = 0.0707, Fisher’s exact test), while other AGS associated gene-deficient fibroblasts showed even lower R-loop accumulation in comparison to that of healthy control (S1D Fig).