ATM and xeroderma pigmentosum: Dozens of genes, including Nijmegen Breakage Syndrome 1 (NBS1), ATM, ATR, xeroderma pigmentosum (XP), and CSB (among others, reviewed in Barzilai et al., 2008; O’Driscoll and Jeggo, 2008), which have functions in DNA damage signaling, activation of DDR pathways, and SSB and DSB repair pathways, have been characterized only as a result of their association to neurological diseases, including early and late onset.