ATRX and myotonic dystrophy type 1: Indeed, CGG repeat expansion in a fragile X model is independent of DSBR-mediated by Pol θ, RAD52, RAD54 or RAD54B100, and loss of Rad 52 or Rad54 has little effect on somatic CTG expansion in the brains of myotonic dystrophy type 1 (DM1) mice99.