FANCD2 and Friedreich ataxia: Compared with Fancc−/− mice lacking FANCC, a component of the FA core complex, Helqgt/gt mice exhibited a mild of form of FA-like phenotypes including hypogonadism and cellular sensitivity to the crosslinker mitomycin C. However, unlike Fancc−/− primary fibroblasts, Helqgt/gt cells had intact FANCD2 mono-ubiquitination and focus formation.