RAD50 and early-onset autosomal dominant Alzheimer disease: ,81 The MRN complex, consisting of MRE11 (meiotic recombination 11), RAD50 (DNA repair protein RAD50) and NBS1 (Nijmegen breakage syndrome 1), is involved in DNA damage sensing and was found to be expressed at substantially lower levels in cortical neurons of Alzheimer’s disease brain samples compared to control samples.82